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* [PATCH 1/2] apparmor: Use a memory pool instead per-CPU caches
@ 2019-04-05 13:34 Sebastian Andrzej Siewior
  2019-04-05 13:34 ` [PATCH 2/2] apparmor: Switch to GFP_KERNEL where possible Sebastian Andrzej Siewior
                   ` (2 more replies)
  0 siblings, 3 replies; 20+ messages in thread
From: Sebastian Andrzej Siewior @ 2019-04-05 13:34 UTC (permalink / raw)
  To: linux-security-module
  Cc: John Johansen, James Morris, Serge E. Hallyn, tglx,
	Sebastian Andrzej Siewior

The get_buffers() macro may provide one or two buffers to the caller.
Those buffers are preallocated on init for each CPU. By default it
allocates
	2* 2 * MAX_PATH * POSSIBLE_CPU

which equals 64KiB on a system with 4 CPUs or 1MiB with 64 CPUs and so
on.

Replace the per-CPU buffers with a common memory pool which is shared
across all CPUs. The pool grows on demand and never shrinks.
By using this pool it is possible to request a buffer and keeping
preemption enabled which avoids the hack in profile_transition().

During light testing I didn't get more than two buffers in total with
this patch. So it seems to make sense to allocate the buffers on demand
and keep them for further use for a quick access.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 security/apparmor/domain.c       | 19 ++-----
 security/apparmor/file.c         | 15 +++---
 security/apparmor/include/path.h | 49 +----------------
 security/apparmor/lsm.c          | 90 +++++++++++++++-----------------
 security/apparmor/mount.c        | 36 ++++++++-----
 5 files changed, 77 insertions(+), 132 deletions(-)

diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
index ca2dccf5b445e..1f4a6e420b6d3 100644
--- a/security/apparmor/domain.c
+++ b/security/apparmor/domain.c
@@ -689,20 +689,9 @@ static struct aa_label *profile_transition(struct aa_profile *profile,
 	} else if (COMPLAIN_MODE(profile)) {
 		/* no exec permission - learning mode */
 		struct aa_profile *new_profile = NULL;
-		char *n = kstrdup(name, GFP_ATOMIC);
 
-		if (n) {
-			/* name is ptr into buffer */
-			long pos = name - buffer;
-			/* break per cpu buffer hold */
-			put_buffers(buffer);
-			new_profile = aa_new_null_profile(profile, false, n,
-							  GFP_KERNEL);
-			get_buffers(buffer);
-			name = buffer + pos;
-			strcpy((char *)name, n);
-			kfree(n);
-		}
+		new_profile = aa_new_null_profile(profile, false, name,
+						  GFP_KERNEL);
 		if (!new_profile) {
 			error = -ENOMEM;
 			info = "could not create null profile";
@@ -907,7 +896,7 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
 		ctx->nnp = aa_get_label(label);
 
 	/* buffer freed below, name is pointer into buffer */
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
 	/* Test for onexec first as onexec override other x transitions. */
 	if (ctx->onexec)
 		new = handle_onexec(label, ctx->onexec, ctx->token,
@@ -979,7 +968,7 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
 
 done:
 	aa_put_label(label);
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 
diff --git a/security/apparmor/file.c b/security/apparmor/file.c
index d0afed9ebd0ed..e422a3f59e80c 100644
--- a/security/apparmor/file.c
+++ b/security/apparmor/file.c
@@ -336,12 +336,12 @@ int aa_path_perm(const char *op, struct aa_label *label,
 
 	flags |= PATH_DELEGATE_DELETED | (S_ISDIR(cond->mode) ? PATH_IS_DIR :
 								0);
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
 	error = fn_for_each_confined(label, profile,
 			profile_path_perm(op, profile, path, buffer, request,
 					  cond, flags, &perms));
 
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
@@ -479,12 +479,13 @@ int aa_path_link(struct aa_label *label, struct dentry *old_dentry,
 	int error;
 
 	/* buffer freed below, lname is pointer in buffer */
-	get_buffers(buffer, buffer2);
+	buffer = aa_get_buffer();
+	buffer2 = aa_get_buffer();
 	error = fn_for_each_confined(label, profile,
 			profile_path_link(profile, &link, buffer, &target,
 					  buffer2, &cond));
-	put_buffers(buffer, buffer2);
-
+	aa_put_buffer(buffer);
+	aa_put_buffer(buffer2);
 	return error;
 }
 
@@ -528,7 +529,7 @@ static int __file_path_perm(const char *op, struct aa_label *label,
 		return 0;
 
 	flags = PATH_DELEGATE_DELETED | (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0);
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
 
 	/* check every profile in task label not in current cache */
 	error = fn_for_each_not_in_set(flabel, label, profile,
@@ -557,7 +558,7 @@ static int __file_path_perm(const char *op, struct aa_label *label,
 	if (!error)
 		update_file_ctx(file_ctx(file), label, request);
 
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
diff --git a/security/apparmor/include/path.h b/security/apparmor/include/path.h
index b6380c5f00972..b0b2ab85e42d8 100644
--- a/security/apparmor/include/path.h
+++ b/security/apparmor/include/path.h
@@ -15,7 +15,6 @@
 #ifndef __AA_PATH_H
 #define __AA_PATH_H
 
-
 enum path_flags {
 	PATH_IS_DIR = 0x1,		/* path is a directory */
 	PATH_CONNECT_PATH = 0x4,	/* connect disconnected paths to / */
@@ -30,51 +29,7 @@ int aa_path_name(const struct path *path, int flags, char *buffer,
 		 const char **name, const char **info,
 		 const char *disconnected);
 
-#define MAX_PATH_BUFFERS 2
-
-/* Per cpu buffers used during mediation */
-/* preallocated buffers to use during path lookups */
-struct aa_buffers {
-	char *buf[MAX_PATH_BUFFERS];
-};
-
-#include <linux/percpu.h>
-#include <linux/preempt.h>
-
-DECLARE_PER_CPU(struct aa_buffers, aa_buffers);
-
-#define ASSIGN(FN, A, X, N) ((X) = FN(A, N))
-#define EVAL1(FN, A, X) ASSIGN(FN, A, X, 0) /*X = FN(0)*/
-#define EVAL2(FN, A, X, Y...)	\
-	do { ASSIGN(FN, A, X, 1);  EVAL1(FN, A, Y); } while (0)
-#define EVAL(FN, A, X...) CONCATENATE(EVAL, COUNT_ARGS(X))(FN, A, X)
-
-#define for_each_cpu_buffer(I) for ((I) = 0; (I) < MAX_PATH_BUFFERS; (I)++)
-
-#ifdef CONFIG_DEBUG_PREEMPT
-#define AA_BUG_PREEMPT_ENABLED(X) AA_BUG(preempt_count() <= 0, X)
-#else
-#define AA_BUG_PREEMPT_ENABLED(X) /* nop */
-#endif
-
-#define __get_buffer(C, N) ({						\
-	AA_BUG_PREEMPT_ENABLED("__get_buffer without preempt disabled");  \
-	(C)->buf[(N)]; })
-
-#define __get_buffers(C, X...)    EVAL(__get_buffer, C, X)
-
-#define __put_buffers(X, Y...) ((void)&(X))
-
-#define get_buffers(X...)						\
-do {									\
-	struct aa_buffers *__cpu_var = get_cpu_ptr(&aa_buffers);	\
-	__get_buffers(__cpu_var, X);					\
-} while (0)
-
-#define put_buffers(X, Y...)		\
-do {					\
-	__put_buffers(X, Y);		\
-	put_cpu_ptr(&aa_buffers);	\
-} while (0)
+char *aa_get_buffer(void);
+void aa_put_buffer(char *buf);
 
 #endif /* __AA_PATH_H */
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 49d664ddff444..224a99b12bc54 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -47,8 +47,13 @@
 /* Flag indicating whether initialization completed */
 int apparmor_initialized;
 
-DEFINE_PER_CPU(struct aa_buffers, aa_buffers);
-
+/* aa_g_path_max */
+union aa_buffer {
+	struct list_head list;
+	char buffer[1];
+};
+static LIST_HEAD(aa_global_buffers);
+static DEFINE_SPINLOCK(aa_buffers_lock);
 
 /*
  * LSM hook functions
@@ -1399,6 +1404,7 @@ static int param_set_aauint(const char *val, const struct kernel_param *kp)
 		return -EPERM;
 
 	error = param_set_uint(val, kp);
+	aa_g_path_max = min_t(uint32_t, aa_g_path_max, sizeof(union aa_buffer));
 	pr_info("AppArmor: buffer size set to %d bytes\n", aa_g_path_max);
 
 	return error;
@@ -1471,6 +1477,38 @@ static int param_set_mode(const char *val, const struct kernel_param *kp)
 	return 0;
 }
 
+char *aa_get_buffer(void)
+{
+	union aa_buffer *aa_buf;
+
+try_again:
+	spin_lock(&aa_buffers_lock);
+	if (!list_empty(&aa_global_buffers)) {
+		aa_buf = list_first_entry(&aa_global_buffers, union aa_buffer,
+					  list);
+		list_del(&aa_buf->list);
+		spin_unlock(&aa_buffers_lock);
+		return &aa_buf->buffer[0];
+	}
+	spin_unlock(&aa_buffers_lock);
+
+	aa_buf = kmalloc(aa_g_path_max, GFP_KERNEL);
+	if (WARN_ON_ONCE(!aa_buf))
+		goto try_again;
+	return &aa_buf->buffer[0];
+}
+
+void aa_put_buffer(char *buf)
+{
+	union aa_buffer *aa_buf;
+
+	aa_buf = container_of(buf, union aa_buffer, buffer[0]);
+
+	spin_lock(&aa_buffers_lock);
+	list_add(&aa_buf->list, &aa_global_buffers);
+	spin_unlock(&aa_buffers_lock);
+}
+
 /*
  * AppArmor init functions
  */
@@ -1489,43 +1527,6 @@ static int __init set_init_ctx(void)
 	return 0;
 }
 
-static void destroy_buffers(void)
-{
-	u32 i, j;
-
-	for_each_possible_cpu(i) {
-		for_each_cpu_buffer(j) {
-			kfree(per_cpu(aa_buffers, i).buf[j]);
-			per_cpu(aa_buffers, i).buf[j] = NULL;
-		}
-	}
-}
-
-static int __init alloc_buffers(void)
-{
-	u32 i, j;
-
-	for_each_possible_cpu(i) {
-		for_each_cpu_buffer(j) {
-			char *buffer;
-
-			if (cpu_to_node(i) > num_online_nodes())
-				/* fallback to kmalloc for offline nodes */
-				buffer = kmalloc(aa_g_path_max, GFP_KERNEL);
-			else
-				buffer = kmalloc_node(aa_g_path_max, GFP_KERNEL,
-						      cpu_to_node(i));
-			if (!buffer) {
-				destroy_buffers();
-				return -ENOMEM;
-			}
-			per_cpu(aa_buffers, i).buf[j] = buffer;
-		}
-	}
-
-	return 0;
-}
-
 #ifdef CONFIG_SYSCTL
 static int apparmor_dointvec(struct ctl_table *table, int write,
 			     void __user *buffer, size_t *lenp, loff_t *ppos)
@@ -1684,17 +1685,11 @@ static int __init apparmor_init(void)
 
 	}
 
-	error = alloc_buffers();
-	if (error) {
-		AA_ERROR("Unable to allocate work buffers\n");
-		goto buffers_out;
-	}
-
 	error = set_init_ctx();
 	if (error) {
 		AA_ERROR("Failed to set context on init task\n");
 		aa_free_root_ns();
-		goto buffers_out;
+		goto alloc_out;
 	}
 	security_add_hooks(apparmor_hooks, ARRAY_SIZE(apparmor_hooks),
 				"apparmor");
@@ -1710,9 +1705,6 @@ static int __init apparmor_init(void)
 
 	return error;
 
-buffers_out:
-	destroy_buffers();
-
 alloc_out:
 	aa_destroy_aafs();
 	aa_teardown_dfa_engine();
diff --git a/security/apparmor/mount.c b/security/apparmor/mount.c
index 8c3787399356b..8a6cf1c14e82a 100644
--- a/security/apparmor/mount.c
+++ b/security/apparmor/mount.c
@@ -412,11 +412,11 @@ int aa_remount(struct aa_label *label, const struct path *path,
 
 	binary = path->dentry->d_sb->s_type->fs_flags & FS_BINARY_MOUNTDATA;
 
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
 	error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, NULL, NULL, NULL,
 				  flags, data, binary));
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
@@ -441,11 +441,13 @@ int aa_bind_mount(struct aa_label *label, const struct path *path,
 	if (error)
 		return error;
 
-	get_buffers(buffer, old_buffer);
+	buffer = aa_get_buffer();
+	old_buffer = aa_get_buffer();
 	error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, &old_path, old_buffer,
 				  NULL, flags, NULL, false));
-	put_buffers(buffer, old_buffer);
+	aa_put_buffer(buffer);
+	aa_put_buffer(old_buffer);
 	path_put(&old_path);
 
 	return error;
@@ -465,11 +467,11 @@ int aa_mount_change_type(struct aa_label *label, const struct path *path,
 	flags &= (MS_REC | MS_SILENT | MS_SHARED | MS_PRIVATE | MS_SLAVE |
 		  MS_UNBINDABLE);
 
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
 	error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, NULL, NULL, NULL,
 				  flags, NULL, false));
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
@@ -492,11 +494,13 @@ int aa_move_mount(struct aa_label *label, const struct path *path,
 	if (error)
 		return error;
 
-	get_buffers(buffer, old_buffer);
+	buffer = aa_get_buffer();
+	old_buffer = aa_get_buffer();
 	error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, &old_path, old_buffer,
 				  NULL, MS_MOVE, NULL, false));
-	put_buffers(buffer, old_buffer);
+	aa_put_buffer(buffer);
+	aa_put_buffer(old_buffer);
 	path_put(&old_path);
 
 	return error;
@@ -537,17 +541,19 @@ int aa_new_mount(struct aa_label *label, const char *dev_name,
 		}
 	}
 
-	get_buffers(buffer, dev_buffer);
+	buffer = aa_get_buffer();
 	if (dev_path) {
 		error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, dev_path, dev_buffer,
 				  type, flags, data, binary));
 	} else {
+		dev_buffer = aa_get_buffer();
 		error = fn_for_each_confined(label, profile,
 			match_mnt_path_str(profile, path, buffer, dev_name,
 					   type, flags, data, binary, NULL));
+		aa_put_buffer(dev_buffer);
 	}
-	put_buffers(buffer, dev_buffer);
+	aa_put_buffer(buffer);
 	if (dev_path)
 		path_put(dev_path);
 
@@ -595,10 +601,10 @@ int aa_umount(struct aa_label *label, struct vfsmount *mnt, int flags)
 	AA_BUG(!label);
 	AA_BUG(!mnt);
 
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
 	error = fn_for_each_confined(label, profile,
 			profile_umount(profile, &path, buffer));
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
@@ -671,7 +677,8 @@ int aa_pivotroot(struct aa_label *label, const struct path *old_path,
 	AA_BUG(!old_path);
 	AA_BUG(!new_path);
 
-	get_buffers(old_buffer, new_buffer);
+	old_buffer = aa_get_buffer();
+	new_buffer = aa_get_buffer();
 	target = fn_label_build(label, profile, GFP_ATOMIC,
 			build_pivotroot(profile, new_path, new_buffer,
 					old_path, old_buffer));
@@ -690,7 +697,8 @@ int aa_pivotroot(struct aa_label *label, const struct path *old_path,
 		/* already audited error */
 		error = PTR_ERR(target);
 out:
-	put_buffers(old_buffer, new_buffer);
+	aa_put_buffer(old_buffer);
+	aa_put_buffer(new_buffer);
 
 	return error;
 
-- 
2.20.1


^ permalink raw reply	[flat|nested] 20+ messages in thread

* [PATCH 2/2] apparmor: Switch to GFP_KERNEL where possible
  2019-04-05 13:34 [PATCH 1/2] apparmor: Use a memory pool instead per-CPU caches Sebastian Andrzej Siewior
@ 2019-04-05 13:34 ` Sebastian Andrzej Siewior
  2019-05-07 19:57   ` John Johansen
  2019-04-15 10:50 ` [PATCH 1/2] apparmor: Use a memory pool instead per-CPU caches Sebastian Andrzej Siewior
  2019-04-28 23:56 ` John Johansen
  2 siblings, 1 reply; 20+ messages in thread
From: Sebastian Andrzej Siewior @ 2019-04-05 13:34 UTC (permalink / raw)
  To: linux-security-module
  Cc: John Johansen, James Morris, Serge E. Hallyn, tglx,
	Sebastian Andrzej Siewior

After removing preempt_disable() from get_buffers() it is possible to
replace a few GFP_ATOMIC allocations with GFP_KERNEL.

Replace GFP_ATOMIC allocations with GFP_KERNEL where the context looks
to bee preepmtible.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 security/apparmor/domain.c | 20 ++++++++++----------
 security/apparmor/file.c   |  2 +-
 security/apparmor/mount.c  |  2 +-
 3 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
index 1f4a6e420b6d3..b8114d9988bac 100644
--- a/security/apparmor/domain.c
+++ b/security/apparmor/domain.c
@@ -524,7 +524,7 @@ struct aa_label *x_table_lookup(struct aa_profile *profile, u32 xindex,
 				label = &new_profile->label;
 			continue;
 		}
-		label = aa_label_parse(&profile->label, *name, GFP_ATOMIC,
+		label = aa_label_parse(&profile->label, *name, GFP_KERNEL,
 				       true, false);
 		if (IS_ERR(label))
 			label = NULL;
@@ -604,7 +604,7 @@ static struct aa_label *x_to_label(struct aa_profile *profile,
 		/* base the stack on post domain transition */
 		struct aa_label *base = new;
 
-		new = aa_label_parse(base, stack, GFP_ATOMIC, true, false);
+		new = aa_label_parse(base, stack, GFP_KERNEL, true, false);
 		if (IS_ERR(new))
 			new = NULL;
 		aa_put_label(base);
@@ -712,7 +712,7 @@ static struct aa_label *profile_transition(struct aa_profile *profile,
 		if (DEBUG_ON) {
 			dbg_printk("apparmor: scrubbing environment variables"
 				   " for %s profile=", name);
-			aa_label_printk(new, GFP_ATOMIC);
+			aa_label_printk(new, GFP_KERNEL);
 			dbg_printk("\n");
 		}
 		*secure_exec = true;
@@ -788,7 +788,7 @@ static int profile_onexec(struct aa_profile *profile, struct aa_label *onexec,
 		if (DEBUG_ON) {
 			dbg_printk("apparmor: scrubbing environment "
 				   "variables for %s label=", xname);
-			aa_label_printk(onexec, GFP_ATOMIC);
+			aa_label_printk(onexec, GFP_KERNEL);
 			dbg_printk("\n");
 		}
 		*secure_exec = true;
@@ -822,7 +822,7 @@ static struct aa_label *handle_onexec(struct aa_label *label,
 					       bprm, buffer, cond, unsafe));
 		if (error)
 			return ERR_PTR(error);
-		new = fn_label_build_in_ns(label, profile, GFP_ATOMIC,
+		new = fn_label_build_in_ns(label, profile, GFP_KERNEL,
 				aa_get_newest_label(onexec),
 				profile_transition(profile, bprm, buffer,
 						   cond, unsafe));
@@ -834,9 +834,9 @@ static struct aa_label *handle_onexec(struct aa_label *label,
 					       buffer, cond, unsafe));
 		if (error)
 			return ERR_PTR(error);
-		new = fn_label_build_in_ns(label, profile, GFP_ATOMIC,
+		new = fn_label_build_in_ns(label, profile, GFP_KERNEL,
 				aa_label_merge(&profile->label, onexec,
-					       GFP_ATOMIC),
+					       GFP_KERNEL),
 				profile_transition(profile, bprm, buffer,
 						   cond, unsafe));
 	}
@@ -902,7 +902,7 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
 		new = handle_onexec(label, ctx->onexec, ctx->token,
 				    bprm, buffer, &cond, &unsafe);
 	else
-		new = fn_label_build(label, profile, GFP_ATOMIC,
+		new = fn_label_build(label, profile, GFP_KERNEL,
 				profile_transition(profile, bprm, buffer,
 						   &cond, &unsafe));
 
@@ -946,7 +946,7 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
 		if (DEBUG_ON) {
 			dbg_printk("scrubbing environment variables for %s "
 				   "label=", bprm->filename);
-			aa_label_printk(new, GFP_ATOMIC);
+			aa_label_printk(new, GFP_KERNEL);
 			dbg_printk("\n");
 		}
 		bprm->secureexec = 1;
@@ -957,7 +957,7 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
 		if (DEBUG_ON) {
 			dbg_printk("apparmor: clearing unsafe personality "
 				   "bits. %s label=", bprm->filename);
-			aa_label_printk(new, GFP_ATOMIC);
+			aa_label_printk(new, GFP_KERNEL);
 			dbg_printk("\n");
 		}
 		bprm->per_clear |= PER_CLEAR_ON_SETID;
diff --git a/security/apparmor/file.c b/security/apparmor/file.c
index e422a3f59e80c..3eb2c5369711c 100644
--- a/security/apparmor/file.c
+++ b/security/apparmor/file.c
@@ -80,7 +80,7 @@ static void file_audit_cb(struct audit_buffer *ab, void *va)
 	if (aad(sa)->peer) {
 		audit_log_format(ab, " target=");
 		aa_label_xaudit(ab, labels_ns(aad(sa)->label), aad(sa)->peer,
-				FLAG_VIEW_SUBNS, GFP_ATOMIC);
+				FLAG_VIEW_SUBNS, GFP_KERNEL);
 	} else if (aad(sa)->fs.target) {
 		audit_log_format(ab, " target=");
 		audit_log_untrustedstring(ab, aad(sa)->fs.target);
diff --git a/security/apparmor/mount.c b/security/apparmor/mount.c
index 8a6cf1c14e82a..d73bc3ceaf9f5 100644
--- a/security/apparmor/mount.c
+++ b/security/apparmor/mount.c
@@ -679,7 +679,7 @@ int aa_pivotroot(struct aa_label *label, const struct path *old_path,
 
 	old_buffer = aa_get_buffer();
 	new_buffer = aa_get_buffer();
-	target = fn_label_build(label, profile, GFP_ATOMIC,
+	target = fn_label_build(label, profile, GFP_KERNEL,
 			build_pivotroot(profile, new_path, new_buffer,
 					old_path, old_buffer));
 	if (!target) {
-- 
2.20.1


^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH 1/2] apparmor: Use a memory pool instead per-CPU caches
  2019-04-05 13:34 [PATCH 1/2] apparmor: Use a memory pool instead per-CPU caches Sebastian Andrzej Siewior
  2019-04-05 13:34 ` [PATCH 2/2] apparmor: Switch to GFP_KERNEL where possible Sebastian Andrzej Siewior
@ 2019-04-15 10:50 ` Sebastian Andrzej Siewior
  2019-04-28 23:56 ` John Johansen
  2 siblings, 0 replies; 20+ messages in thread
From: Sebastian Andrzej Siewior @ 2019-04-15 10:50 UTC (permalink / raw)
  To: linux-security-module, John Johansen, James Morris, Serge E. Hallyn; +Cc: tglx

On 2019-04-05 15:34:57 [+0200], To linux-security-module@vger.kernel.org wrote:
> The get_buffers() macro may provide one or two buffers to the caller.
> Those buffers are preallocated on init for each CPU. By default it
> allocates
> 	2* 2 * MAX_PATH * POSSIBLE_CPU
> 
> which equals 64KiB on a system with 4 CPUs or 1MiB with 64 CPUs and so
> on.
> 
> Replace the per-CPU buffers with a common memory pool which is shared
> across all CPUs. The pool grows on demand and never shrinks.
> By using this pool it is possible to request a buffer and keeping
> preemption enabled which avoids the hack in profile_transition().
> 
> During light testing I didn't get more than two buffers in total with
> this patch. So it seems to make sense to allocate the buffers on demand
> and keep them for further use for a quick access.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

a gentle ping.

Sebastian

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH 1/2] apparmor: Use a memory pool instead per-CPU caches
  2019-04-05 13:34 [PATCH 1/2] apparmor: Use a memory pool instead per-CPU caches Sebastian Andrzej Siewior
  2019-04-05 13:34 ` [PATCH 2/2] apparmor: Switch to GFP_KERNEL where possible Sebastian Andrzej Siewior
  2019-04-15 10:50 ` [PATCH 1/2] apparmor: Use a memory pool instead per-CPU caches Sebastian Andrzej Siewior
@ 2019-04-28 23:56 ` John Johansen
  2019-04-30 14:47   ` Sebastian Andrzej Siewior
  2 siblings, 1 reply; 20+ messages in thread
From: John Johansen @ 2019-04-28 23:56 UTC (permalink / raw)
  To: Sebastian Andrzej Siewior, linux-security-module
  Cc: James Morris, Serge E. Hallyn, tglx

On 4/5/19 6:34 AM, Sebastian Andrzej Siewior wrote:
> The get_buffers() macro may provide one or two buffers to the caller.
> Those buffers are preallocated on init for each CPU. By default it
> allocates
> 	2* 2 * MAX_PATH * POSSIBLE_CPU
> 
> which equals 64KiB on a system with 4 CPUs or 1MiB with 64 CPUs and so
> on.
> 
> Replace the per-CPU buffers with a common memory pool which is shared
> across all CPUs. The pool grows on demand and never shrinks.
> By using this pool it is possible to request a buffer and keeping
> preemption enabled which avoids the hack in profile_transition().
> 
> During light testing I didn't get more than two buffers in total with
> this patch. So it seems to make sense to allocate the buffers on demand
> and keep them for further use for a quick access.
> 

So digging into why the history of the per cpu buffers in apparmor.
We used to do buffer allocations via kmalloc and there were a few reasons
for the switch 

* speed/lockless: speaks for it self, mediation is already slow enough

* some buffer allocations had to be done with GFP_ATOMIC, making them
  more likely to fail. Since we fail closed that means failure would
  block access. This actually became a serious problem in a couple
  places. Switching to per cpu buffers and blocking pre-empt was
  the solution.

* in heavy use cases we would see a lot of buffers being allocated
  and freed. Which resulted in locking slow downs and also buffer
  allocation failures. So having the buffers preallocated allowed us
  to bound this potential problem.

This was all 6 years ago. Going to a mem pool certainly could help,
reduce the memory foot print, and would definitely help with
preempt/real time kernels.

A big concern with this patchset is reverting back to GFP_KERNEL
for everything. We definitely were getting failures due to allocations
in atomic context. There have been lots of changes in the kernel over
the last six years so it possible these cases don't exist anymore. I
went through and built some kernels with this patchset and have run
through some testing without tripping that problem but I don't think
it has seen enough testing yet.


> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
>  security/apparmor/domain.c       | 19 ++-----
>  security/apparmor/file.c         | 15 +++---
>  security/apparmor/include/path.h | 49 +----------------
>  security/apparmor/lsm.c          | 90 +++++++++++++++-----------------
>  security/apparmor/mount.c        | 36 ++++++++-----
>  5 files changed, 77 insertions(+), 132 deletions(-)
> 
> diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
> index ca2dccf5b445e..1f4a6e420b6d3 100644
> --- a/security/apparmor/domain.c
> +++ b/security/apparmor/domain.c
> @@ -689,20 +689,9 @@ static struct aa_label *profile_transition(struct aa_profile *profile,
>  	} else if (COMPLAIN_MODE(profile)) {
>  		/* no exec permission - learning mode */
>  		struct aa_profile *new_profile = NULL;
> -		char *n = kstrdup(name, GFP_ATOMIC);
>  
> -		if (n) {
> -			/* name is ptr into buffer */
> -			long pos = name - buffer;
> -			/* break per cpu buffer hold */
> -			put_buffers(buffer);
> -			new_profile = aa_new_null_profile(profile, false, n,
> -							  GFP_KERNEL);
> -			get_buffers(buffer);
> -			name = buffer + pos;
> -			strcpy((char *)name, n);
> -			kfree(n);
> -		}
> +		new_profile = aa_new_null_profile(profile, false, name,
> +						  GFP_KERNEL);
>  		if (!new_profile) {
>  			error = -ENOMEM;
>  			info = "could not create null profile";
> @@ -907,7 +896,7 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
>  		ctx->nnp = aa_get_label(label);
>  
>  	/* buffer freed below, name is pointer into buffer */
> -	get_buffers(buffer);
> +	buffer = aa_get_buffer();
>  	/* Test for onexec first as onexec override other x transitions. */
>  	if (ctx->onexec)
>  		new = handle_onexec(label, ctx->onexec, ctx->token,
> @@ -979,7 +968,7 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
>  
>  done:
>  	aa_put_label(label);
> -	put_buffers(buffer);
> +	aa_put_buffer(buffer);
>  
>  	return error;
>  
> diff --git a/security/apparmor/file.c b/security/apparmor/file.c
> index d0afed9ebd0ed..e422a3f59e80c 100644
> --- a/security/apparmor/file.c
> +++ b/security/apparmor/file.c
> @@ -336,12 +336,12 @@ int aa_path_perm(const char *op, struct aa_label *label,
>  
>  	flags |= PATH_DELEGATE_DELETED | (S_ISDIR(cond->mode) ? PATH_IS_DIR :
>  								0);
> -	get_buffers(buffer);
> +	buffer = aa_get_buffer();
>  	error = fn_for_each_confined(label, profile,
>  			profile_path_perm(op, profile, path, buffer, request,
>  					  cond, flags, &perms));
>  
> -	put_buffers(buffer);
> +	aa_put_buffer(buffer);
>  
>  	return error;
>  }
> @@ -479,12 +479,13 @@ int aa_path_link(struct aa_label *label, struct dentry *old_dentry,
>  	int error;
>  
>  	/* buffer freed below, lname is pointer in buffer */
> -	get_buffers(buffer, buffer2);
> +	buffer = aa_get_buffer();
> +	buffer2 = aa_get_buffer();
>  	error = fn_for_each_confined(label, profile,
>  			profile_path_link(profile, &link, buffer, &target,
>  					  buffer2, &cond));
> -	put_buffers(buffer, buffer2);
> -
> +	aa_put_buffer(buffer);
> +	aa_put_buffer(buffer2);
>  	return error;
>  }
>  
> @@ -528,7 +529,7 @@ static int __file_path_perm(const char *op, struct aa_label *label,
>  		return 0;
>  
>  	flags = PATH_DELEGATE_DELETED | (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0);
> -	get_buffers(buffer);
> +	buffer = aa_get_buffer();
>  
>  	/* check every profile in task label not in current cache */
>  	error = fn_for_each_not_in_set(flabel, label, profile,
> @@ -557,7 +558,7 @@ static int __file_path_perm(const char *op, struct aa_label *label,
>  	if (!error)
>  		update_file_ctx(file_ctx(file), label, request);
>  
> -	put_buffers(buffer);
> +	aa_put_buffer(buffer);
>  
>  	return error;
>  }
> diff --git a/security/apparmor/include/path.h b/security/apparmor/include/path.h
> index b6380c5f00972..b0b2ab85e42d8 100644
> --- a/security/apparmor/include/path.h
> +++ b/security/apparmor/include/path.h
> @@ -15,7 +15,6 @@
>  #ifndef __AA_PATH_H
>  #define __AA_PATH_H
>  
> -
>  enum path_flags {
>  	PATH_IS_DIR = 0x1,		/* path is a directory */
>  	PATH_CONNECT_PATH = 0x4,	/* connect disconnected paths to / */
> @@ -30,51 +29,7 @@ int aa_path_name(const struct path *path, int flags, char *buffer,
>  		 const char **name, const char **info,
>  		 const char *disconnected);
>  
> -#define MAX_PATH_BUFFERS 2
> -
> -/* Per cpu buffers used during mediation */
> -/* preallocated buffers to use during path lookups */
> -struct aa_buffers {
> -	char *buf[MAX_PATH_BUFFERS];
> -};
> -
> -#include <linux/percpu.h>
> -#include <linux/preempt.h>
> -
> -DECLARE_PER_CPU(struct aa_buffers, aa_buffers);
> -
> -#define ASSIGN(FN, A, X, N) ((X) = FN(A, N))
> -#define EVAL1(FN, A, X) ASSIGN(FN, A, X, 0) /*X = FN(0)*/
> -#define EVAL2(FN, A, X, Y...)	\
> -	do { ASSIGN(FN, A, X, 1);  EVAL1(FN, A, Y); } while (0)
> -#define EVAL(FN, A, X...) CONCATENATE(EVAL, COUNT_ARGS(X))(FN, A, X)
> -
> -#define for_each_cpu_buffer(I) for ((I) = 0; (I) < MAX_PATH_BUFFERS; (I)++)
> -
> -#ifdef CONFIG_DEBUG_PREEMPT
> -#define AA_BUG_PREEMPT_ENABLED(X) AA_BUG(preempt_count() <= 0, X)
> -#else
> -#define AA_BUG_PREEMPT_ENABLED(X) /* nop */
> -#endif
> -
> -#define __get_buffer(C, N) ({						\
> -	AA_BUG_PREEMPT_ENABLED("__get_buffer without preempt disabled");  \
> -	(C)->buf[(N)]; })
> -
> -#define __get_buffers(C, X...)    EVAL(__get_buffer, C, X)
> -
> -#define __put_buffers(X, Y...) ((void)&(X))
> -
> -#define get_buffers(X...)						\
> -do {									\
> -	struct aa_buffers *__cpu_var = get_cpu_ptr(&aa_buffers);	\
> -	__get_buffers(__cpu_var, X);					\
> -} while (0)
> -
> -#define put_buffers(X, Y...)		\
> -do {					\
> -	__put_buffers(X, Y);		\
> -	put_cpu_ptr(&aa_buffers);	\
> -} while (0)
> +char *aa_get_buffer(void);
> +void aa_put_buffer(char *buf);
>  
>  #endif /* __AA_PATH_H */
> diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
> index 49d664ddff444..224a99b12bc54 100644
> --- a/security/apparmor/lsm.c
> +++ b/security/apparmor/lsm.c
> @@ -47,8 +47,13 @@
>  /* Flag indicating whether initialization completed */
>  int apparmor_initialized;
>  
> -DEFINE_PER_CPU(struct aa_buffers, aa_buffers);
> -
> +/* aa_g_path_max */
> +union aa_buffer {
> +	struct list_head list;
> +	char buffer[1];
> +};
> +static LIST_HEAD(aa_global_buffers);
> +static DEFINE_SPINLOCK(aa_buffers_lock);
>  
>  /*
>   * LSM hook functions
> @@ -1399,6 +1404,7 @@ static int param_set_aauint(const char *val, const struct kernel_param *kp)
>  		return -EPERM;
>  
>  	error = param_set_uint(val, kp);
> +	aa_g_path_max = min_t(uint32_t, aa_g_path_max, sizeof(union aa_buffer));
>  	pr_info("AppArmor: buffer size set to %d bytes\n", aa_g_path_max);
>  
>  	return error;
> @@ -1471,6 +1477,38 @@ static int param_set_mode(const char *val, const struct kernel_param *kp)
>  	return 0;
>  }
>  
> +char *aa_get_buffer(void)
> +{
> +	union aa_buffer *aa_buf;
> +
> +try_again:
> +	spin_lock(&aa_buffers_lock);
> +	if (!list_empty(&aa_global_buffers)) {
> +		aa_buf = list_first_entry(&aa_global_buffers, union aa_buffer,
> +					  list);
> +		list_del(&aa_buf->list);
> +		spin_unlock(&aa_buffers_lock);
> +		return &aa_buf->buffer[0];
> +	}
> +	spin_unlock(&aa_buffers_lock);
> +
> +	aa_buf = kmalloc(aa_g_path_max, GFP_KERNEL);
> +	if (WARN_ON_ONCE(!aa_buf))
> +		goto try_again;
> +	return &aa_buf->buffer[0];
> +}
> +
> +void aa_put_buffer(char *buf)
> +{
> +	union aa_buffer *aa_buf;
> +
> +	aa_buf = container_of(buf, union aa_buffer, buffer[0]);
> +
> +	spin_lock(&aa_buffers_lock);
> +	list_add(&aa_buf->list, &aa_global_buffers);
> +	spin_unlock(&aa_buffers_lock);
> +}
> +
>  /*
>   * AppArmor init functions
>   */
> @@ -1489,43 +1527,6 @@ static int __init set_init_ctx(void)
>  	return 0;
>  }
>  
> -static void destroy_buffers(void)
> -{
> -	u32 i, j;
> -
> -	for_each_possible_cpu(i) {
> -		for_each_cpu_buffer(j) {
> -			kfree(per_cpu(aa_buffers, i).buf[j]);
> -			per_cpu(aa_buffers, i).buf[j] = NULL;
> -		}
> -	}
> -}
> -
> -static int __init alloc_buffers(void)
> -{
> -	u32 i, j;
> -
> -	for_each_possible_cpu(i) {
> -		for_each_cpu_buffer(j) {
> -			char *buffer;
> -
> -			if (cpu_to_node(i) > num_online_nodes())
> -				/* fallback to kmalloc for offline nodes */
> -				buffer = kmalloc(aa_g_path_max, GFP_KERNEL);
> -			else
> -				buffer = kmalloc_node(aa_g_path_max, GFP_KERNEL,
> -						      cpu_to_node(i));
> -			if (!buffer) {
> -				destroy_buffers();
> -				return -ENOMEM;
> -			}
> -			per_cpu(aa_buffers, i).buf[j] = buffer;
> -		}
> -	}
> -
> -	return 0;
> -}
> -
>  #ifdef CONFIG_SYSCTL
>  static int apparmor_dointvec(struct ctl_table *table, int write,
>  			     void __user *buffer, size_t *lenp, loff_t *ppos)
> @@ -1684,17 +1685,11 @@ static int __init apparmor_init(void)
>  
>  	}
>  
> -	error = alloc_buffers();
> -	if (error) {
> -		AA_ERROR("Unable to allocate work buffers\n");
> -		goto buffers_out;
> -	}
> -
>  	error = set_init_ctx();
>  	if (error) {
>  		AA_ERROR("Failed to set context on init task\n");
>  		aa_free_root_ns();
> -		goto buffers_out;
> +		goto alloc_out;
>  	}
>  	security_add_hooks(apparmor_hooks, ARRAY_SIZE(apparmor_hooks),
>  				"apparmor");
> @@ -1710,9 +1705,6 @@ static int __init apparmor_init(void)
>  
>  	return error;
>  
> -buffers_out:
> -	destroy_buffers();
> -
>  alloc_out:
>  	aa_destroy_aafs();
>  	aa_teardown_dfa_engine();
> diff --git a/security/apparmor/mount.c b/security/apparmor/mount.c
> index 8c3787399356b..8a6cf1c14e82a 100644
> --- a/security/apparmor/mount.c
> +++ b/security/apparmor/mount.c
> @@ -412,11 +412,11 @@ int aa_remount(struct aa_label *label, const struct path *path,
>  
>  	binary = path->dentry->d_sb->s_type->fs_flags & FS_BINARY_MOUNTDATA;
>  
> -	get_buffers(buffer);
> +	buffer = aa_get_buffer();
>  	error = fn_for_each_confined(label, profile,
>  			match_mnt(profile, path, buffer, NULL, NULL, NULL,
>  				  flags, data, binary));
> -	put_buffers(buffer);
> +	aa_put_buffer(buffer);
>  
>  	return error;
>  }
> @@ -441,11 +441,13 @@ int aa_bind_mount(struct aa_label *label, const struct path *path,
>  	if (error)
>  		return error;
>  
> -	get_buffers(buffer, old_buffer);
> +	buffer = aa_get_buffer();
> +	old_buffer = aa_get_buffer();
>  	error = fn_for_each_confined(label, profile,
>  			match_mnt(profile, path, buffer, &old_path, old_buffer,
>  				  NULL, flags, NULL, false));
> -	put_buffers(buffer, old_buffer);
> +	aa_put_buffer(buffer);
> +	aa_put_buffer(old_buffer);
>  	path_put(&old_path);
>  
>  	return error;
> @@ -465,11 +467,11 @@ int aa_mount_change_type(struct aa_label *label, const struct path *path,
>  	flags &= (MS_REC | MS_SILENT | MS_SHARED | MS_PRIVATE | MS_SLAVE |
>  		  MS_UNBINDABLE);
>  
> -	get_buffers(buffer);
> +	buffer = aa_get_buffer();
>  	error = fn_for_each_confined(label, profile,
>  			match_mnt(profile, path, buffer, NULL, NULL, NULL,
>  				  flags, NULL, false));
> -	put_buffers(buffer);
> +	aa_put_buffer(buffer);
>  
>  	return error;
>  }
> @@ -492,11 +494,13 @@ int aa_move_mount(struct aa_label *label, const struct path *path,
>  	if (error)
>  		return error;
>  
> -	get_buffers(buffer, old_buffer);
> +	buffer = aa_get_buffer();
> +	old_buffer = aa_get_buffer();
>  	error = fn_for_each_confined(label, profile,
>  			match_mnt(profile, path, buffer, &old_path, old_buffer,
>  				  NULL, MS_MOVE, NULL, false));
> -	put_buffers(buffer, old_buffer);
> +	aa_put_buffer(buffer);
> +	aa_put_buffer(old_buffer);
>  	path_put(&old_path);
>  
>  	return error;
> @@ -537,17 +541,19 @@ int aa_new_mount(struct aa_label *label, const char *dev_name,
>  		}
>  	}
>  
> -	get_buffers(buffer, dev_buffer);
> +	buffer = aa_get_buffer();
>  	if (dev_path) {
>  		error = fn_for_each_confined(label, profile,
>  			match_mnt(profile, path, buffer, dev_path, dev_buffer,
>  				  type, flags, data, binary));
>  	} else {
> +		dev_buffer = aa_get_buffer();
>  		error = fn_for_each_confined(label, profile,
>  			match_mnt_path_str(profile, path, buffer, dev_name,
>  					   type, flags, data, binary, NULL));
> +		aa_put_buffer(dev_buffer);
>  	}
> -	put_buffers(buffer, dev_buffer);
> +	aa_put_buffer(buffer);
>  	if (dev_path)
>  		path_put(dev_path);
>  
> @@ -595,10 +601,10 @@ int aa_umount(struct aa_label *label, struct vfsmount *mnt, int flags)
>  	AA_BUG(!label);
>  	AA_BUG(!mnt);
>  
> -	get_buffers(buffer);
> +	buffer = aa_get_buffer();
>  	error = fn_for_each_confined(label, profile,
>  			profile_umount(profile, &path, buffer));
> -	put_buffers(buffer);
> +	aa_put_buffer(buffer);
>  
>  	return error;
>  }
> @@ -671,7 +677,8 @@ int aa_pivotroot(struct aa_label *label, const struct path *old_path,
>  	AA_BUG(!old_path);
>  	AA_BUG(!new_path);
>  
> -	get_buffers(old_buffer, new_buffer);
> +	old_buffer = aa_get_buffer();
> +	new_buffer = aa_get_buffer();
>  	target = fn_label_build(label, profile, GFP_ATOMIC,
>  			build_pivotroot(profile, new_path, new_buffer,
>  					old_path, old_buffer));
> @@ -690,7 +697,8 @@ int aa_pivotroot(struct aa_label *label, const struct path *old_path,
>  		/* already audited error */
>  		error = PTR_ERR(target);
>  out:
> -	put_buffers(old_buffer, new_buffer);
> +	aa_put_buffer(old_buffer);
> +	aa_put_buffer(new_buffer);
>  
>  	return error;
>  
> 


^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH 1/2] apparmor: Use a memory pool instead per-CPU caches
  2019-04-28 23:56 ` John Johansen
@ 2019-04-30 14:47   ` Sebastian Andrzej Siewior
  2019-05-01 21:29     ` John Johansen
  0 siblings, 1 reply; 20+ messages in thread
From: Sebastian Andrzej Siewior @ 2019-04-30 14:47 UTC (permalink / raw)
  To: John Johansen; +Cc: linux-security-module, James Morris, Serge E. Hallyn, tglx

On 2019-04-28 16:56:59 [-0700], John Johansen wrote:
> So digging into why the history of the per cpu buffers in apparmor.
> We used to do buffer allocations via kmalloc and there were a few reasons
> for the switch 
> 
> * speed/lockless: speaks for it self, mediation is already slow enough

it is shared among all CPUs but it is a small/quick operation to
add/return a buffer.

> * some buffer allocations had to be done with GFP_ATOMIC, making them
>   more likely to fail. Since we fail closed that means failure would
>   block access. This actually became a serious problem in a couple
>   places. Switching to per cpu buffers and blocking pre-empt was
>   the solution.

GFP_KERNEL is allowed to use IO/SWAP and ATOMIC has emergency pools. The
new approach won't return a NULL pointer, simply spin to either allocate
new memory or get one which was just returned.

> * in heavy use cases we would see a lot of buffers being allocated
>   and freed. Which resulted in locking slow downs and also buffer
>   allocation failures. So having the buffers preallocated allowed us
>   to bound this potential problem.
> 
> This was all 6 years ago. Going to a mem pool certainly could help,
> reduce the memory foot print, and would definitely help with
> preempt/real time kernels.
> 
> A big concern with this patchset is reverting back to GFP_KERNEL
> for everything. We definitely were getting failures due to allocations
> in atomic context. There have been lots of changes in the kernel over
> the last six years so it possible these cases don't exist anymore. I
> went through and built some kernels with this patchset and have run
> through some testing without tripping that problem but I don't think
> it has seen enough testing yet.

Do you want apply #1 now and #2 later? I audited the ATOMIC->KERNEL
changes manually and I didn't see any atomic context. It looked like the
only reason for ATOMIC was the preempt_disable() due to the memory pool.

Sebastian

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH 1/2] apparmor: Use a memory pool instead per-CPU caches
  2019-04-30 14:47   ` Sebastian Andrzej Siewior
@ 2019-05-01 21:29     ` John Johansen
  2019-05-02 10:51       ` Sebastian Andrzej Siewior
  0 siblings, 1 reply; 20+ messages in thread
From: John Johansen @ 2019-05-01 21:29 UTC (permalink / raw)
  To: Sebastian Andrzej Siewior
  Cc: linux-security-module, James Morris, Serge E. Hallyn, tglx

On 4/30/19 7:47 AM, Sebastian Andrzej Siewior wrote:
> On 2019-04-28 16:56:59 [-0700], John Johansen wrote:
>> So digging into why the history of the per cpu buffers in apparmor.
>> We used to do buffer allocations via kmalloc and there were a few reasons
>> for the switch 
>>
>> * speed/lockless: speaks for it self, mediation is already slow enough
> 
> it is shared among all CPUs but it is a small/quick operation to
> add/return a buffer.
> 
I wouldn't exactly call taking a lock speedy. Getting an available buffer
or returning it is indeed quick. The allocation fall back not so much.


>> * some buffer allocations had to be done with GFP_ATOMIC, making them
>>   more likely to fail. Since we fail closed that means failure would
>>   block access. This actually became a serious problem in a couple
>>   places. Switching to per cpu buffers and blocking pre-empt was
>>   the solution.
> 
> GFP_KERNEL is allowed to use IO/SWAP and ATOMIC has emergency pools. The
> new approach won't return a NULL pointer, simply spin to either allocate
> new memory or get one which was just returned.
> 

yeah, I am not really a fan of a potential infinite loop trying to allocate
memory. It may be worth retrying once or twice but potentially infinitely
spinning on failed allocation really isn't acceptable.

>> * in heavy use cases we would see a lot of buffers being allocated
>>   and freed. Which resulted in locking slow downs and also buffer
>>   allocation failures. So having the buffers preallocated allowed us
>>   to bound this potential problem.
>>
>> This was all 6 years ago. Going to a mem pool certainly could help,
>> reduce the memory foot print, and would definitely help with
>> preempt/real time kernels.
>>
>> A big concern with this patchset is reverting back to GFP_KERNEL
>> for everything. We definitely were getting failures due to allocations
>> in atomic context. There have been lots of changes in the kernel over
>> the last six years so it possible these cases don't exist anymore. I
>> went through and built some kernels with this patchset and have run
>> through some testing without tripping that problem but I don't think
>> it has seen enough testing yet.
> 
> Do you want apply #1 now and #2 later? I audited the ATOMIC->KERNEL
> changes manually and I didn't see any atomic context. It looked like the
> only reason for ATOMIC was the preempt_disable() due to the memory pool.
> 

Indeed most if not all (I'd have to dig to be sure) the changes made in #2
were original done because of the move to the per cpu buffers and blocking
pre-emption.

The problem was with the allocation of the buffer needing to be GFP_ATOMIC
some times.

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH 1/2] apparmor: Use a memory pool instead per-CPU caches
  2019-05-01 21:29     ` John Johansen
@ 2019-05-02 10:51       ` Sebastian Andrzej Siewior
  2019-05-02 13:17         ` Tetsuo Handa
  2019-05-02 19:33         ` [PATCH 1/2] " John Johansen
  0 siblings, 2 replies; 20+ messages in thread
From: Sebastian Andrzej Siewior @ 2019-05-02 10:51 UTC (permalink / raw)
  To: John Johansen; +Cc: linux-security-module, James Morris, Serge E. Hallyn, tglx

On 2019-05-01 14:29:17 [-0700], John Johansen wrote:
> On 4/30/19 7:47 AM, Sebastian Andrzej Siewior wrote:
> > On 2019-04-28 16:56:59 [-0700], John Johansen wrote:
> >> So digging into why the history of the per cpu buffers in apparmor.
> >> We used to do buffer allocations via kmalloc and there were a few reasons
> >> for the switch 
> >>
> >> * speed/lockless: speaks for it self, mediation is already slow enough
> > 
> > it is shared among all CPUs but it is a small/quick operation to
> > add/return a buffer.
> > 
> I wouldn't exactly call taking a lock speedy. Getting an available buffer
> or returning it is indeed quick. The allocation fall back not so much.

Based on testing it happens only in the beginning. We could also start
with 2,3,4 pre allocated buffers or so.
My testing was most likely limited and I did not exceed two.

> >> * some buffer allocations had to be done with GFP_ATOMIC, making them
> >>   more likely to fail. Since we fail closed that means failure would
> >>   block access. This actually became a serious problem in a couple
> >>   places. Switching to per cpu buffers and blocking pre-empt was
> >>   the solution.
> > 
> > GFP_KERNEL is allowed to use IO/SWAP and ATOMIC has emergency pools. The
> > new approach won't return a NULL pointer, simply spin to either allocate
> > new memory or get one which was just returned.
> > 
> 
> yeah, I am not really a fan of a potential infinite loop trying to allocate
> memory. It may be worth retrying once or twice but potentially infinitely
> spinning on failed allocation really isn't acceptable.

It shouldn't spin infinitely because even if kmalloc() does not return
any memory, one of the other CPUs should return their buffer at some
point. However, if you don't like it I could add two retries and return
NULL + fixup callers. On the other hand if the other CPUs BUG() with the
buffers then yes, we may spin.
So limited retries it is?

> >> * in heavy use cases we would see a lot of buffers being allocated
> >>   and freed. Which resulted in locking slow downs and also buffer
> >>   allocation failures. So having the buffers preallocated allowed us
> >>   to bound this potential problem.
> >>
> >> This was all 6 years ago. Going to a mem pool certainly could help,
> >> reduce the memory foot print, and would definitely help with
> >> preempt/real time kernels.
> >>
> >> A big concern with this patchset is reverting back to GFP_KERNEL
> >> for everything. We definitely were getting failures due to allocations
> >> in atomic context. There have been lots of changes in the kernel over
> >> the last six years so it possible these cases don't exist anymore. I
> >> went through and built some kernels with this patchset and have run
> >> through some testing without tripping that problem but I don't think
> >> it has seen enough testing yet.
> > 
> > Do you want apply #1 now and #2 later? I audited the ATOMIC->KERNEL
> > changes manually and I didn't see any atomic context. It looked like the
> > only reason for ATOMIC was the preempt_disable() due to the memory pool.
> > 
> 
> Indeed most if not all (I'd have to dig to be sure) the changes made in #2
> were original done because of the move to the per cpu buffers and blocking
> pre-emption.
> 
> The problem was with the allocation of the buffer needing to be GFP_ATOMIC
> some times.
yup, that is what I saw, too.

Sebastian

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH 1/2] apparmor: Use a memory pool instead per-CPU caches
  2019-05-02 10:51       ` Sebastian Andrzej Siewior
@ 2019-05-02 13:17         ` Tetsuo Handa
  2019-05-02 13:47           ` Sebastian Andrzej Siewior
  2019-05-02 19:33         ` [PATCH 1/2] " John Johansen
  1 sibling, 1 reply; 20+ messages in thread
From: Tetsuo Handa @ 2019-05-02 13:17 UTC (permalink / raw)
  To: Sebastian Andrzej Siewior, John Johansen
  Cc: linux-security-module, James Morris, Serge E. Hallyn, tglx

On 2019/05/02 19:51, Sebastian Andrzej Siewior wrote:
>>>> * some buffer allocations had to be done with GFP_ATOMIC, making them
>>>>   more likely to fail. Since we fail closed that means failure would
>>>>   block access. This actually became a serious problem in a couple
>>>>   places. Switching to per cpu buffers and blocking pre-empt was
>>>>   the solution.
>>>
>>> GFP_KERNEL is allowed to use IO/SWAP and ATOMIC has emergency pools. The
>>> new approach won't return a NULL pointer, simply spin to either allocate
>>> new memory or get one which was just returned.
>>>
>>
>> yeah, I am not really a fan of a potential infinite loop trying to allocate
>> memory. It may be worth retrying once or twice but potentially infinitely
>> spinning on failed allocation really isn't acceptable.
> 
> It shouldn't spin infinitely because even if kmalloc() does not return
> any memory, one of the other CPUs should return their buffer at some
> point. However, if you don't like it I could add two retries and return
> NULL + fixup callers. On the other hand if the other CPUs BUG() with the
> buffers then yes, we may spin.
> So limited retries it is?

There is 'The "too small to fail" memory-allocation rule'
( https://lwn.net/Articles/627419/ ) where GFP_KERNEL allocation for
size <= 32768 bytes never fails unless current thread was killed by
the OOM killer. This means that kmalloc() in

+char *aa_get_buffer(void)
+{
+	union aa_buffer *aa_buf;
+
+try_again:
+	spin_lock(&aa_buffers_lock);
+	if (!list_empty(&aa_global_buffers)) {
+		aa_buf = list_first_entry(&aa_global_buffers, union aa_buffer,
+					  list);
+		list_del(&aa_buf->list);
+		spin_unlock(&aa_buffers_lock);
+		return &aa_buf->buffer[0];
+	}
+	spin_unlock(&aa_buffers_lock);
+
+	aa_buf = kmalloc(aa_g_path_max, GFP_KERNEL);
+	if (WARN_ON_ONCE(!aa_buf))
+		goto try_again;
+	return &aa_buf->buffer[0];
+}

can't return NULL unless current thread was killed by the OOM killer
if aa_g_path_max <= 32768. On the other hand, if aa_g_path_max > 32768,
this allocation can easily fail, and retrying forever is very bad.

If current thread was killed by the OOM killer, current thread should be
able to bail out without retrying. If allocation can never succeed (e.g.
aa_g_path_max == 1073741824 was specified), we must bail out.



By the way, did you really test your patch?

> @@ -1399,6 +1404,7 @@ static int param_set_aauint(const char *val, const struct kernel_param *kp)
>  		return -EPERM;
>  
>  	error = param_set_uint(val, kp);
> +	aa_g_path_max = min_t(uint32_t, aa_g_path_max, sizeof(union aa_buffer));

I think that this will guarantee that aa_g_path_max <= sizeof(struct list_head)
which is too small to succeed. :-(

>  	pr_info("AppArmor: buffer size set to %d bytes\n", aa_g_path_max);
>  
>  	return error;


^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH 1/2] apparmor: Use a memory pool instead per-CPU caches
  2019-05-02 13:17         ` Tetsuo Handa
@ 2019-05-02 13:47           ` Sebastian Andrzej Siewior
  2019-05-02 14:10             ` Tetsuo Handa
  0 siblings, 1 reply; 20+ messages in thread
From: Sebastian Andrzej Siewior @ 2019-05-02 13:47 UTC (permalink / raw)
  To: Tetsuo Handa
  Cc: John Johansen, linux-security-module, James Morris,
	Serge E. Hallyn, tglx

On 2019-05-02 22:17:35 [+0900], Tetsuo Handa wrote:
> There is 'The "too small to fail" memory-allocation rule'
> ( https://lwn.net/Articles/627419/ ) where GFP_KERNEL allocation for
> size <= 32768 bytes never fails unless current thread was killed by
> the OOM killer. This means that kmalloc() in
> 
> +char *aa_get_buffer(void)
> +{
> +	union aa_buffer *aa_buf;
> +
> +try_again:
> +	spin_lock(&aa_buffers_lock);
> +	if (!list_empty(&aa_global_buffers)) {
> +		aa_buf = list_first_entry(&aa_global_buffers, union aa_buffer,
> +					  list);
> +		list_del(&aa_buf->list);
> +		spin_unlock(&aa_buffers_lock);
> +		return &aa_buf->buffer[0];
> +	}
> +	spin_unlock(&aa_buffers_lock);
> +
> +	aa_buf = kmalloc(aa_g_path_max, GFP_KERNEL);
> +	if (WARN_ON_ONCE(!aa_buf))
> +		goto try_again;
> +	return &aa_buf->buffer[0];
> +}
> 
> can't return NULL unless current thread was killed by the OOM killer
> if aa_g_path_max <= 32768. On the other hand, if aa_g_path_max > 32768,
> this allocation can easily fail, and retrying forever is very bad.

as I pointed out in the other email, it shouldn't retry forever because
we should have something in the pool which will be returned.

> If current thread was killed by the OOM killer, current thread should be
> able to bail out without retrying. If allocation can never succeed (e.g.
> aa_g_path_max == 1073741824 was specified), we must bail out.

okay. That is obviously too much and we would loop, indeed.

> By the way, did you really test your patch?

I booted Debian on a 112 core which has apparmor enabled and debian
ships a few profiles. And then I used the box for a while.

> > @@ -1399,6 +1404,7 @@ static int param_set_aauint(const char *val, const struct kernel_param *kp)
> >  		return -EPERM;
> >  
> >  	error = param_set_uint(val, kp);
> > +	aa_g_path_max = min_t(uint32_t, aa_g_path_max, sizeof(union aa_buffer));
> 
> I think that this will guarantee that aa_g_path_max <= sizeof(struct list_head)
> which is too small to succeed. :-(

Ach right, this should have been max instead of min. Btw: are there any
sane upper/lower limits while at it?

> >  	pr_info("AppArmor: buffer size set to %d bytes\n", aa_g_path_max);
> >  
> >  	return error;

Sebastian

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH 1/2] apparmor: Use a memory pool instead per-CPU caches
  2019-05-02 13:47           ` Sebastian Andrzej Siewior
@ 2019-05-02 14:10             ` Tetsuo Handa
  2019-05-03 11:48               ` [PATCH v2] " Sebastian Andrzej Siewior
  0 siblings, 1 reply; 20+ messages in thread
From: Tetsuo Handa @ 2019-05-02 14:10 UTC (permalink / raw)
  To: Sebastian Andrzej Siewior
  Cc: John Johansen, linux-security-module, James Morris,
	Serge E. Hallyn, tglx

On 2019/05/02 22:47, Sebastian Andrzej Siewior wrote:
> On 2019-05-02 22:17:35 [+0900], Tetsuo Handa wrote:
>> There is 'The "too small to fail" memory-allocation rule'
>> ( https://lwn.net/Articles/627419/ ) where GFP_KERNEL allocation for
>> size <= 32768 bytes never fails unless current thread was killed by
>> the OOM killer. This means that kmalloc() in
>>
>> +char *aa_get_buffer(void)
>> +{
>> +	union aa_buffer *aa_buf;
>> +
>> +try_again:
>> +	spin_lock(&aa_buffers_lock);
>> +	if (!list_empty(&aa_global_buffers)) {
>> +		aa_buf = list_first_entry(&aa_global_buffers, union aa_buffer,
>> +					  list);
>> +		list_del(&aa_buf->list);
>> +		spin_unlock(&aa_buffers_lock);
>> +		return &aa_buf->buffer[0];
>> +	}
>> +	spin_unlock(&aa_buffers_lock);
>> +
>> +	aa_buf = kmalloc(aa_g_path_max, GFP_KERNEL);
>> +	if (WARN_ON_ONCE(!aa_buf))
>> +		goto try_again;
>> +	return &aa_buf->buffer[0];
>> +}
>>
>> can't return NULL unless current thread was killed by the OOM killer
>> if aa_g_path_max <= 32768. On the other hand, if aa_g_path_max > 32768,
>> this allocation can easily fail, and retrying forever is very bad.
> 
> as I pointed out in the other email, it shouldn't retry forever because
> we should have something in the pool which will be returned.
> 

The point of 'The "too small to fail" memory-allocation rule' is that kmalloc(GFP_KERNEL)
can't return NULL after current thread once reached kmalloc(GFP_KERNEL). That is, current
thread loops forever inside __alloc_pages_nodemask() unless killed by the OOM killer.
If you want to use aa_get_buffer() as if a memory pool, you need to specify __GFP_NORETRY
(or __GFP_RETRY_MAYFAIL).



>>> @@ -1399,6 +1404,7 @@ static int param_set_aauint(const char *val, const struct kernel_param *kp)
>>>  		return -EPERM;
>>>  
>>>  	error = param_set_uint(val, kp);
>>> +	aa_g_path_max = min_t(uint32_t, aa_g_path_max, sizeof(union aa_buffer));
>>
>> I think that this will guarantee that aa_g_path_max <= sizeof(struct list_head)
>> which is too small to succeed. :-(
> 
> Ach right, this should have been max instead of min. Btw: are there any
> sane upper/lower limits while at it?

Although PATH_MAX is a limit which can be passed as a string argument to syscalls,
there is no limit for a pathname calculated by d_path() etc. The pathname can grow
until memory allocation for dentry cache fails after OOM-killer killed almost all
userspace processes.

But for pathname based access control, returning an error to userspace due to memory
allocation failure for d_path() etc. might result in unexpected termination of that
process. Therefore, you don't want to give up easily.

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH 1/2] apparmor: Use a memory pool instead per-CPU caches
  2019-05-02 10:51       ` Sebastian Andrzej Siewior
  2019-05-02 13:17         ` Tetsuo Handa
@ 2019-05-02 19:33         ` " John Johansen
  1 sibling, 0 replies; 20+ messages in thread
From: John Johansen @ 2019-05-02 19:33 UTC (permalink / raw)
  To: Sebastian Andrzej Siewior
  Cc: linux-security-module, James Morris, Serge E. Hallyn, tglx

On 5/2/19 3:51 AM, Sebastian Andrzej Siewior wrote:
> On 2019-05-01 14:29:17 [-0700], John Johansen wrote:
>> On 4/30/19 7:47 AM, Sebastian Andrzej Siewior wrote:
>>> On 2019-04-28 16:56:59 [-0700], John Johansen wrote:
>>>> So digging into why the history of the per cpu buffers in apparmor.
>>>> We used to do buffer allocations via kmalloc and there were a few reasons
>>>> for the switch 
>>>>
>>>> * speed/lockless: speaks for it self, mediation is already slow enough
>>>
>>> it is shared among all CPUs but it is a small/quick operation to
>>> add/return a buffer.
>>>
>> I wouldn't exactly call taking a lock speedy. Getting an available buffer
>> or returning it is indeed quick. The allocation fall back not so much.
> 
> Based on testing it happens only in the beginning. We could also start
> with 2,3,4 pre allocated buffers or so.
> My testing was most likely limited and I did not exceed two.
> 

yeah lets have a few preallocated

>>>> * some buffer allocations had to be done with GFP_ATOMIC, making them
>>>>   more likely to fail. Since we fail closed that means failure would
>>>>   block access. This actually became a serious problem in a couple
>>>>   places. Switching to per cpu buffers and blocking pre-empt was
>>>>   the solution.
>>>
>>> GFP_KERNEL is allowed to use IO/SWAP and ATOMIC has emergency pools. The
>>> new approach won't return a NULL pointer, simply spin to either allocate
>>> new memory or get one which was just returned.
>>>
>>
>> yeah, I am not really a fan of a potential infinite loop trying to allocate
>> memory. It may be worth retrying once or twice but potentially infinitely
>> spinning on failed allocation really isn't acceptable.
> 
> It shouldn't spin infinitely because even if kmalloc() does not return
> any memory, one of the other CPUs should return their buffer at some
> point. However, if you don't like it I could add two retries and return
> NULL + fixup callers. On the other hand if the other CPUs BUG() with the
> buffers then yes, we may spin.
> So limited retries it is?
> 
yes please


^ permalink raw reply	[flat|nested] 20+ messages in thread

* [PATCH v2] apparmor: Use a memory pool instead per-CPU caches
  2019-05-02 14:10             ` Tetsuo Handa
@ 2019-05-03 11:48               ` " Sebastian Andrzej Siewior
  2019-05-03 11:51                 ` [PATCH v3] " Sebastian Andrzej Siewior
  0 siblings, 1 reply; 20+ messages in thread
From: Sebastian Andrzej Siewior @ 2019-05-03 11:48 UTC (permalink / raw)
  To: Tetsuo Handa
  Cc: John Johansen, linux-security-module, James Morris,
	Serge E. Hallyn, tglx

The get_buffers() macro may provide one or two buffers to the caller.
Those buffers are pre-allocated on init for each CPU. By default it
allocates
	2* 2 * MAX_PATH * POSSIBLE_CPU

which equals 64KiB on a system with 4 CPUs or 1MiB with 64 CPUs and so
on.

Replace the per-CPU buffers with a common memory pool which is shared
across all CPUs. The pool grows on demand and never shrinks. The pool
starts with two (UP) or four (SMP) elements. By using this pool it is
possible to request a buffer and keeping preemption enabled which avoids
the hack in profile_transition().

It has been pointed out by Tetsuo Handa that GFP_KERNEL allocations for
small amount of memory do not fail. In order not to have an endless
retry, __GFP_RETRY_MAYFAIL is passed (so the memory allocation is not
repeated until success) and retried once hoping that in the meantime a
buffer has been returned to the pool. Since now NULL is possible all
allocation paths check the buffer pointer and return -ENOMEM on failure.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
v1…v2:
   - Use max_t instead min_t for a minimal buffer.
   - Pre-allocate 2 buffers on UP and 4 buffers on SMP systems.
   - Use __GFP_RETRY_MAYFAIL | __GFP_NOWARN on memory allocation. The
     allocation may fail under pressure and we will retry once.
   - Add an error path to each caller of aa_get_buffer() if the memory
     allocation fails.

 security/apparmor/domain.c       |  24 +++----
 security/apparmor/file.c         |  24 +++++--
 security/apparmor/include/path.h |  49 +-------------
 security/apparmor/lsm.c          | 106 +++++++++++++++++++++++--------
 security/apparmor/mount.c        |  65 +++++++++++++++----
 5 files changed, 160 insertions(+), 108 deletions(-)

diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
index ca2dccf5b445e..cae0e619ff4fe 100644
--- a/security/apparmor/domain.c
+++ b/security/apparmor/domain.c
@@ -689,20 +689,9 @@ static struct aa_label *profile_transition(struct aa_profile *profile,
 	} else if (COMPLAIN_MODE(profile)) {
 		/* no exec permission - learning mode */
 		struct aa_profile *new_profile = NULL;
-		char *n = kstrdup(name, GFP_ATOMIC);
 
-		if (n) {
-			/* name is ptr into buffer */
-			long pos = name - buffer;
-			/* break per cpu buffer hold */
-			put_buffers(buffer);
-			new_profile = aa_new_null_profile(profile, false, n,
-							  GFP_KERNEL);
-			get_buffers(buffer);
-			name = buffer + pos;
-			strcpy((char *)name, n);
-			kfree(n);
-		}
+		new_profile = aa_new_null_profile(profile, false, name,
+						  GFP_KERNEL);
 		if (!new_profile) {
 			error = -ENOMEM;
 			info = "could not create null profile";
@@ -907,7 +896,12 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
 		ctx->nnp = aa_get_label(label);
 
 	/* buffer freed below, name is pointer into buffer */
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
+	if (!buffer) {
+		error = -ENOMEM;
+		goto done;
+	}
+
 	/* Test for onexec first as onexec override other x transitions. */
 	if (ctx->onexec)
 		new = handle_onexec(label, ctx->onexec, ctx->token,
@@ -979,7 +973,7 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
 
 done:
 	aa_put_label(label);
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 
diff --git a/security/apparmor/file.c b/security/apparmor/file.c
index d0afed9ebd0ed..7b424e73a8c74 100644
--- a/security/apparmor/file.c
+++ b/security/apparmor/file.c
@@ -336,12 +336,14 @@ int aa_path_perm(const char *op, struct aa_label *label,
 
 	flags |= PATH_DELEGATE_DELETED | (S_ISDIR(cond->mode) ? PATH_IS_DIR :
 								0);
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
+	if (!buffer)
+		return -ENOMEM;
 	error = fn_for_each_confined(label, profile,
 			profile_path_perm(op, profile, path, buffer, request,
 					  cond, flags, &perms));
 
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
@@ -479,12 +481,18 @@ int aa_path_link(struct aa_label *label, struct dentry *old_dentry,
 	int error;
 
 	/* buffer freed below, lname is pointer in buffer */
-	get_buffers(buffer, buffer2);
+	buffer = aa_get_buffer();
+	buffer2 = aa_get_buffer();
+	error = -ENOMEM;
+	if (!buffer || !buffer2)
+		goto out;
+
 	error = fn_for_each_confined(label, profile,
 			profile_path_link(profile, &link, buffer, &target,
 					  buffer2, &cond));
-	put_buffers(buffer, buffer2);
-
+out:
+	aa_put_buffer(buffer);
+	aa_put_buffer(buffer2);
 	return error;
 }
 
@@ -528,7 +536,9 @@ static int __file_path_perm(const char *op, struct aa_label *label,
 		return 0;
 
 	flags = PATH_DELEGATE_DELETED | (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0);
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
+	if (!buffer)
+		return -ENOMEM;
 
 	/* check every profile in task label not in current cache */
 	error = fn_for_each_not_in_set(flabel, label, profile,
@@ -557,7 +567,7 @@ static int __file_path_perm(const char *op, struct aa_label *label,
 	if (!error)
 		update_file_ctx(file_ctx(file), label, request);
 
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
diff --git a/security/apparmor/include/path.h b/security/apparmor/include/path.h
index b6380c5f00972..b0b2ab85e42d8 100644
--- a/security/apparmor/include/path.h
+++ b/security/apparmor/include/path.h
@@ -15,7 +15,6 @@
 #ifndef __AA_PATH_H
 #define __AA_PATH_H
 
-
 enum path_flags {
 	PATH_IS_DIR = 0x1,		/* path is a directory */
 	PATH_CONNECT_PATH = 0x4,	/* connect disconnected paths to / */
@@ -30,51 +29,7 @@ int aa_path_name(const struct path *path, int flags, char *buffer,
 		 const char **name, const char **info,
 		 const char *disconnected);
 
-#define MAX_PATH_BUFFERS 2
-
-/* Per cpu buffers used during mediation */
-/* preallocated buffers to use during path lookups */
-struct aa_buffers {
-	char *buf[MAX_PATH_BUFFERS];
-};
-
-#include <linux/percpu.h>
-#include <linux/preempt.h>
-
-DECLARE_PER_CPU(struct aa_buffers, aa_buffers);
-
-#define ASSIGN(FN, A, X, N) ((X) = FN(A, N))
-#define EVAL1(FN, A, X) ASSIGN(FN, A, X, 0) /*X = FN(0)*/
-#define EVAL2(FN, A, X, Y...)	\
-	do { ASSIGN(FN, A, X, 1);  EVAL1(FN, A, Y); } while (0)
-#define EVAL(FN, A, X...) CONCATENATE(EVAL, COUNT_ARGS(X))(FN, A, X)
-
-#define for_each_cpu_buffer(I) for ((I) = 0; (I) < MAX_PATH_BUFFERS; (I)++)
-
-#ifdef CONFIG_DEBUG_PREEMPT
-#define AA_BUG_PREEMPT_ENABLED(X) AA_BUG(preempt_count() <= 0, X)
-#else
-#define AA_BUG_PREEMPT_ENABLED(X) /* nop */
-#endif
-
-#define __get_buffer(C, N) ({						\
-	AA_BUG_PREEMPT_ENABLED("__get_buffer without preempt disabled");  \
-	(C)->buf[(N)]; })
-
-#define __get_buffers(C, X...)    EVAL(__get_buffer, C, X)
-
-#define __put_buffers(X, Y...) ((void)&(X))
-
-#define get_buffers(X...)						\
-do {									\
-	struct aa_buffers *__cpu_var = get_cpu_ptr(&aa_buffers);	\
-	__get_buffers(__cpu_var, X);					\
-} while (0)
-
-#define put_buffers(X, Y...)		\
-do {					\
-	__put_buffers(X, Y);		\
-	put_cpu_ptr(&aa_buffers);	\
-} while (0)
+char *aa_get_buffer(void);
+void aa_put_buffer(char *buf);
 
 #endif /* __AA_PATH_H */
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 87500bde5a92d..942702dc3c0a2 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -47,8 +47,13 @@
 /* Flag indicating whether initialization completed */
 int apparmor_initialized;
 
-DEFINE_PER_CPU(struct aa_buffers, aa_buffers);
+union aa_buffer {
+	struct list_head list;
+	char buffer[1];
+};
 
+static LIST_HEAD(aa_global_buffers);
+static DEFINE_SPINLOCK(aa_buffers_lock);
 
 /*
  * LSM hook functions
@@ -1406,6 +1411,7 @@ static int param_set_aauint(const char *val, const struct kernel_param *kp)
 		return -EPERM;
 
 	error = param_set_uint(val, kp);
+	aa_g_path_max = max_t(uint32_t, aa_g_path_max, sizeof(union aa_buffer));
 	pr_info("AppArmor: buffer size set to %d bytes\n", aa_g_path_max);
 
 	return error;
@@ -1518,6 +1524,46 @@ static int param_set_mode(const char *val, const struct kernel_param *kp)
 	return 0;
 }
 
+char *aa_get_buffer(void)
+{
+	union aa_buffer *aa_buf;
+	bool try_again = true;
+
+retry:
+	spin_lock(&aa_buffers_lock);
+	if (!list_empty(&aa_global_buffers)) {
+		aa_buf = list_first_entry(&aa_global_buffers, union aa_buffer,
+					  list);
+		list_del(&aa_buf->list);
+		spin_unlock(&aa_buffers_lock);
+		return &aa_buf->buffer[0];
+	}
+	spin_unlock(&aa_buffers_lock);
+
+	aa_buf = kmalloc(aa_g_path_max, GFP_KERNEL | __GFP_RETRY_MAYFAIL |
+			 __GFP_NOWARN);
+	if (!aa_buf) {
+		if (try_again) {
+			try_again = false;
+			goto retry;
+		}
+		pr_warn_once("AppArmor: Failed to allocate a memory buffer.\n");
+		return NULL;
+	}
+	return &aa_buf->buffer[0];
+}
+
+void aa_put_buffer(char *buf)
+{
+	union aa_buffer *aa_buf;
+
+	aa_buf = container_of(buf, union aa_buffer, buffer[0]);
+
+	spin_lock(&aa_buffers_lock);
+	list_add(&aa_buf->list, &aa_global_buffers);
+	spin_unlock(&aa_buffers_lock);
+}
+
 /*
  * AppArmor init functions
  */
@@ -1538,38 +1584,49 @@ static int __init set_init_ctx(void)
 
 static void destroy_buffers(void)
 {
-	u32 i, j;
+	union aa_buffer *aa_buf;
 
-	for_each_possible_cpu(i) {
-		for_each_cpu_buffer(j) {
-			kfree(per_cpu(aa_buffers, i).buf[j]);
-			per_cpu(aa_buffers, i).buf[j] = NULL;
-		}
+	spin_lock(&aa_buffers_lock);
+	while (!list_empty(&aa_global_buffers)) {
+		aa_buf = list_first_entry(&aa_global_buffers, union aa_buffer,
+					 list);
+		list_del(&aa_buf->list);
+		spin_unlock(&aa_buffers_lock);
+		kfree(aa_buf);
+		spin_lock(&aa_buffers_lock);
 	}
+	spin_unlock(&aa_buffers_lock);
 }
 
 static int __init alloc_buffers(void)
 {
-	u32 i, j;
+	union aa_buffer *aa_buf;
+	int i, num;
 
-	for_each_possible_cpu(i) {
-		for_each_cpu_buffer(j) {
-			char *buffer;
+	/*
+	 * A function may require two buffers at once. Usually the buffers are
+	 * used for a short period of time and are shared. On UP kernel buffers
+	 * two should be enough, with more CPUs it is possible that more
+	 * buffers will be used simultaneously. The preallocated pool may grow.
+	 * This preallocation has also the side-effect that AppArmor will be
+	 * disabled early at boot if aa_g_path_max is extremly high.
+	 */
+	if (num_online_cpus() > 1)
+		num = 4;
+	else
+		num = 2;
 
-			if (cpu_to_node(i) > num_online_nodes())
-				/* fallback to kmalloc for offline nodes */
-				buffer = kmalloc(aa_g_path_max, GFP_KERNEL);
-			else
-				buffer = kmalloc_node(aa_g_path_max, GFP_KERNEL,
-						      cpu_to_node(i));
-			if (!buffer) {
-				destroy_buffers();
-				return -ENOMEM;
-			}
-			per_cpu(aa_buffers, i).buf[j] = buffer;
+	for (i = 0; i < num; i++) {
+		gfp_t flags;
+
+		aa_buf = kmalloc(aa_g_path_max, GFP_KERNEL |
+				 __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
+		if (!aa_buf) {
+			destroy_buffers();
+			return -ENOMEM;
 		}
+		aa_put_buffer(&aa_buf->buffer[0]);
 	}
-
 	return 0;
 }
 
@@ -1734,7 +1791,7 @@ static int __init apparmor_init(void)
 	error = alloc_buffers();
 	if (error) {
 		AA_ERROR("Unable to allocate work buffers\n");
-		goto buffers_out;
+		goto alloc_out;
 	}
 
 	error = set_init_ctx();
@@ -1759,7 +1816,6 @@ static int __init apparmor_init(void)
 
 buffers_out:
 	destroy_buffers();
-
 alloc_out:
 	aa_destroy_aafs();
 	aa_teardown_dfa_engine();
diff --git a/security/apparmor/mount.c b/security/apparmor/mount.c
index 8c3787399356b..267a26fba14e1 100644
--- a/security/apparmor/mount.c
+++ b/security/apparmor/mount.c
@@ -412,11 +412,13 @@ int aa_remount(struct aa_label *label, const struct path *path,
 
 	binary = path->dentry->d_sb->s_type->fs_flags & FS_BINARY_MOUNTDATA;
 
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
+	if (!buffer)
+		return -ENOMEM;
 	error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, NULL, NULL, NULL,
 				  flags, data, binary));
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
@@ -441,11 +443,18 @@ int aa_bind_mount(struct aa_label *label, const struct path *path,
 	if (error)
 		return error;
 
-	get_buffers(buffer, old_buffer);
+	buffer = aa_get_buffer();
+	old_buffer = aa_get_buffer();
+	error = -ENOMEM;
+	if (!buffer || old_buffer)
+		goto out;
+
 	error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, &old_path, old_buffer,
 				  NULL, flags, NULL, false));
-	put_buffers(buffer, old_buffer);
+out:
+	aa_put_buffer(buffer);
+	aa_put_buffer(old_buffer);
 	path_put(&old_path);
 
 	return error;
@@ -465,11 +474,13 @@ int aa_mount_change_type(struct aa_label *label, const struct path *path,
 	flags &= (MS_REC | MS_SILENT | MS_SHARED | MS_PRIVATE | MS_SLAVE |
 		  MS_UNBINDABLE);
 
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
+	if (!buffer)
+		return -ENOMEM;
 	error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, NULL, NULL, NULL,
 				  flags, NULL, false));
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
@@ -492,11 +503,17 @@ int aa_move_mount(struct aa_label *label, const struct path *path,
 	if (error)
 		return error;
 
-	get_buffers(buffer, old_buffer);
+	buffer = aa_get_buffer();
+	old_buffer = aa_get_buffer();
+	error = -ENOMEM;
+	if (!buffer || !old_buffer)
+		goto out;
 	error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, &old_path, old_buffer,
 				  NULL, MS_MOVE, NULL, false));
-	put_buffers(buffer, old_buffer);
+out:
+	aa_put_buffer(buffer);
+	aa_put_buffer(old_buffer);
 	path_put(&old_path);
 
 	return error;
@@ -537,17 +554,29 @@ int aa_new_mount(struct aa_label *label, const char *dev_name,
 		}
 	}
 
-	get_buffers(buffer, dev_buffer);
+	buffer = aa_get_buffer();
+	if (!buffer) {
+		error = -ENOMEM;
+		goto out;
+	}
 	if (dev_path) {
 		error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, dev_path, dev_buffer,
 				  type, flags, data, binary));
 	} else {
+		dev_buffer = aa_get_buffer();
+		if (!dev_buffer) {
+			error = -ENOMEM;
+			goto out;
+		}
 		error = fn_for_each_confined(label, profile,
 			match_mnt_path_str(profile, path, buffer, dev_name,
 					   type, flags, data, binary, NULL));
 	}
-	put_buffers(buffer, dev_buffer);
+
+out:
+	aa_put_buffer(buffer);
+	aa_put_buffer(dev_buffer);
 	if (dev_path)
 		path_put(dev_path);
 
@@ -595,10 +624,13 @@ int aa_umount(struct aa_label *label, struct vfsmount *mnt, int flags)
 	AA_BUG(!label);
 	AA_BUG(!mnt);
 
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
+	if (!buffer)
+		return -ENOMEM;
+
 	error = fn_for_each_confined(label, profile,
 			profile_umount(profile, &path, buffer));
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
@@ -671,7 +703,11 @@ int aa_pivotroot(struct aa_label *label, const struct path *old_path,
 	AA_BUG(!old_path);
 	AA_BUG(!new_path);
 
-	get_buffers(old_buffer, new_buffer);
+	old_buffer = aa_get_buffer();
+	new_buffer = aa_get_buffer();
+	error = -ENOMEM;
+	if (!old_buffer || !new_buffer)
+		goto out;
 	target = fn_label_build(label, profile, GFP_ATOMIC,
 			build_pivotroot(profile, new_path, new_buffer,
 					old_path, old_buffer));
@@ -690,7 +726,8 @@ int aa_pivotroot(struct aa_label *label, const struct path *old_path,
 		/* already audited error */
 		error = PTR_ERR(target);
 out:
-	put_buffers(old_buffer, new_buffer);
+	aa_put_buffer(old_buffer);
+	aa_put_buffer(new_buffer);
 
 	return error;
 
-- 
2.20.1


^ permalink raw reply	[flat|nested] 20+ messages in thread

* [PATCH v3] apparmor: Use a memory pool instead per-CPU caches
  2019-05-03 11:48               ` [PATCH v2] " Sebastian Andrzej Siewior
@ 2019-05-03 11:51                 ` " Sebastian Andrzej Siewior
  2019-05-03 12:41                   ` Tetsuo Handa
  0 siblings, 1 reply; 20+ messages in thread
From: Sebastian Andrzej Siewior @ 2019-05-03 11:51 UTC (permalink / raw)
  To: Tetsuo Handa
  Cc: John Johansen, linux-security-module, James Morris,
	Serge E. Hallyn, tglx

The get_buffers() macro may provide one or two buffers to the caller.
Those buffers are pre-allocated on init for each CPU. By default it
allocates
	2* 2 * MAX_PATH * POSSIBLE_CPU

which equals 64KiB on a system with 4 CPUs or 1MiB with 64 CPUs and so
on.

Replace the per-CPU buffers with a common memory pool which is shared
across all CPUs. The pool grows on demand and never shrinks. The pool
starts with two (UP) or four (SMP) elements. By using this pool it is
possible to request a buffer and keeping preemption enabled which avoids
the hack in profile_transition().

It has been pointed out by Tetsuo Handa that GFP_KERNEL allocations for
small amount of memory do not fail. In order not to have an endless
retry, __GFP_RETRY_MAYFAIL is passed (so the memory allocation is not
repeated until success) and retried once hoping that in the meantime a
buffer has been returned to the pool. Since now NULL is possible all
allocation paths check the buffer pointer and return -ENOMEM on failure.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
v2…v3:
   - remove an unused flags variable.

v1…v2:
   - Use max_t instead min_t for a minimal buffer.
   - Pre-allocate 2 buffers on UP and 4 buffers on SMP systems.
   - Use __GFP_RETRY_MAYFAIL | __GFP_NOWARN on memory allocation. The
     allocation may fail under pressure and we will retry once.
   - Add an error path to each caller of aa_get_buffer() if the memory
     allocation fails.

 security/apparmor/domain.c       |  24 +++----
 security/apparmor/file.c         |  24 ++++---
 security/apparmor/include/path.h |  49 +--------------
 security/apparmor/lsm.c          | 105 +++++++++++++++++++++++--------
 security/apparmor/mount.c        |  65 ++++++++++++++-----
 5 files changed, 159 insertions(+), 108 deletions(-)

diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
index ca2dccf5b445e..cae0e619ff4fe 100644
--- a/security/apparmor/domain.c
+++ b/security/apparmor/domain.c
@@ -689,20 +689,9 @@ static struct aa_label *profile_transition(struct aa_profile *profile,
 	} else if (COMPLAIN_MODE(profile)) {
 		/* no exec permission - learning mode */
 		struct aa_profile *new_profile = NULL;
-		char *n = kstrdup(name, GFP_ATOMIC);
 
-		if (n) {
-			/* name is ptr into buffer */
-			long pos = name - buffer;
-			/* break per cpu buffer hold */
-			put_buffers(buffer);
-			new_profile = aa_new_null_profile(profile, false, n,
-							  GFP_KERNEL);
-			get_buffers(buffer);
-			name = buffer + pos;
-			strcpy((char *)name, n);
-			kfree(n);
-		}
+		new_profile = aa_new_null_profile(profile, false, name,
+						  GFP_KERNEL);
 		if (!new_profile) {
 			error = -ENOMEM;
 			info = "could not create null profile";
@@ -907,7 +896,12 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
 		ctx->nnp = aa_get_label(label);
 
 	/* buffer freed below, name is pointer into buffer */
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
+	if (!buffer) {
+		error = -ENOMEM;
+		goto done;
+	}
+
 	/* Test for onexec first as onexec override other x transitions. */
 	if (ctx->onexec)
 		new = handle_onexec(label, ctx->onexec, ctx->token,
@@ -979,7 +973,7 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
 
 done:
 	aa_put_label(label);
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 
diff --git a/security/apparmor/file.c b/security/apparmor/file.c
index d0afed9ebd0ed..7b424e73a8c74 100644
--- a/security/apparmor/file.c
+++ b/security/apparmor/file.c
@@ -336,12 +336,14 @@ int aa_path_perm(const char *op, struct aa_label *label,
 
 	flags |= PATH_DELEGATE_DELETED | (S_ISDIR(cond->mode) ? PATH_IS_DIR :
 								0);
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
+	if (!buffer)
+		return -ENOMEM;
 	error = fn_for_each_confined(label, profile,
 			profile_path_perm(op, profile, path, buffer, request,
 					  cond, flags, &perms));
 
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
@@ -479,12 +481,18 @@ int aa_path_link(struct aa_label *label, struct dentry *old_dentry,
 	int error;
 
 	/* buffer freed below, lname is pointer in buffer */
-	get_buffers(buffer, buffer2);
+	buffer = aa_get_buffer();
+	buffer2 = aa_get_buffer();
+	error = -ENOMEM;
+	if (!buffer || !buffer2)
+		goto out;
+
 	error = fn_for_each_confined(label, profile,
 			profile_path_link(profile, &link, buffer, &target,
 					  buffer2, &cond));
-	put_buffers(buffer, buffer2);
-
+out:
+	aa_put_buffer(buffer);
+	aa_put_buffer(buffer2);
 	return error;
 }
 
@@ -528,7 +536,9 @@ static int __file_path_perm(const char *op, struct aa_label *label,
 		return 0;
 
 	flags = PATH_DELEGATE_DELETED | (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0);
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
+	if (!buffer)
+		return -ENOMEM;
 
 	/* check every profile in task label not in current cache */
 	error = fn_for_each_not_in_set(flabel, label, profile,
@@ -557,7 +567,7 @@ static int __file_path_perm(const char *op, struct aa_label *label,
 	if (!error)
 		update_file_ctx(file_ctx(file), label, request);
 
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
diff --git a/security/apparmor/include/path.h b/security/apparmor/include/path.h
index b6380c5f00972..b0b2ab85e42d8 100644
--- a/security/apparmor/include/path.h
+++ b/security/apparmor/include/path.h
@@ -15,7 +15,6 @@
 #ifndef __AA_PATH_H
 #define __AA_PATH_H
 
-
 enum path_flags {
 	PATH_IS_DIR = 0x1,		/* path is a directory */
 	PATH_CONNECT_PATH = 0x4,	/* connect disconnected paths to / */
@@ -30,51 +29,7 @@ int aa_path_name(const struct path *path, int flags, char *buffer,
 		 const char **name, const char **info,
 		 const char *disconnected);
 
-#define MAX_PATH_BUFFERS 2
-
-/* Per cpu buffers used during mediation */
-/* preallocated buffers to use during path lookups */
-struct aa_buffers {
-	char *buf[MAX_PATH_BUFFERS];
-};
-
-#include <linux/percpu.h>
-#include <linux/preempt.h>
-
-DECLARE_PER_CPU(struct aa_buffers, aa_buffers);
-
-#define ASSIGN(FN, A, X, N) ((X) = FN(A, N))
-#define EVAL1(FN, A, X) ASSIGN(FN, A, X, 0) /*X = FN(0)*/
-#define EVAL2(FN, A, X, Y...)	\
-	do { ASSIGN(FN, A, X, 1);  EVAL1(FN, A, Y); } while (0)
-#define EVAL(FN, A, X...) CONCATENATE(EVAL, COUNT_ARGS(X))(FN, A, X)
-
-#define for_each_cpu_buffer(I) for ((I) = 0; (I) < MAX_PATH_BUFFERS; (I)++)
-
-#ifdef CONFIG_DEBUG_PREEMPT
-#define AA_BUG_PREEMPT_ENABLED(X) AA_BUG(preempt_count() <= 0, X)
-#else
-#define AA_BUG_PREEMPT_ENABLED(X) /* nop */
-#endif
-
-#define __get_buffer(C, N) ({						\
-	AA_BUG_PREEMPT_ENABLED("__get_buffer without preempt disabled");  \
-	(C)->buf[(N)]; })
-
-#define __get_buffers(C, X...)    EVAL(__get_buffer, C, X)
-
-#define __put_buffers(X, Y...) ((void)&(X))
-
-#define get_buffers(X...)						\
-do {									\
-	struct aa_buffers *__cpu_var = get_cpu_ptr(&aa_buffers);	\
-	__get_buffers(__cpu_var, X);					\
-} while (0)
-
-#define put_buffers(X, Y...)		\
-do {					\
-	__put_buffers(X, Y);		\
-	put_cpu_ptr(&aa_buffers);	\
-} while (0)
+char *aa_get_buffer(void);
+void aa_put_buffer(char *buf);
 
 #endif /* __AA_PATH_H */
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 87500bde5a92d..d8a3b8fe4de00 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -47,8 +47,13 @@
 /* Flag indicating whether initialization completed */
 int apparmor_initialized;
 
-DEFINE_PER_CPU(struct aa_buffers, aa_buffers);
+union aa_buffer {
+	struct list_head list;
+	char buffer[1];
+};
 
+static LIST_HEAD(aa_global_buffers);
+static DEFINE_SPINLOCK(aa_buffers_lock);
 
 /*
  * LSM hook functions
@@ -1406,6 +1411,7 @@ static int param_set_aauint(const char *val, const struct kernel_param *kp)
 		return -EPERM;
 
 	error = param_set_uint(val, kp);
+	aa_g_path_max = max_t(uint32_t, aa_g_path_max, sizeof(union aa_buffer));
 	pr_info("AppArmor: buffer size set to %d bytes\n", aa_g_path_max);
 
 	return error;
@@ -1518,6 +1524,46 @@ static int param_set_mode(const char *val, const struct kernel_param *kp)
 	return 0;
 }
 
+char *aa_get_buffer(void)
+{
+	union aa_buffer *aa_buf;
+	bool try_again = true;
+
+retry:
+	spin_lock(&aa_buffers_lock);
+	if (!list_empty(&aa_global_buffers)) {
+		aa_buf = list_first_entry(&aa_global_buffers, union aa_buffer,
+					  list);
+		list_del(&aa_buf->list);
+		spin_unlock(&aa_buffers_lock);
+		return &aa_buf->buffer[0];
+	}
+	spin_unlock(&aa_buffers_lock);
+
+	aa_buf = kmalloc(aa_g_path_max, GFP_KERNEL | __GFP_RETRY_MAYFAIL |
+			 __GFP_NOWARN);
+	if (!aa_buf) {
+		if (try_again) {
+			try_again = false;
+			goto retry;
+		}
+		pr_warn_once("AppArmor: Failed to allocate a memory buffer.\n");
+		return NULL;
+	}
+	return &aa_buf->buffer[0];
+}
+
+void aa_put_buffer(char *buf)
+{
+	union aa_buffer *aa_buf;
+
+	aa_buf = container_of(buf, union aa_buffer, buffer[0]);
+
+	spin_lock(&aa_buffers_lock);
+	list_add(&aa_buf->list, &aa_global_buffers);
+	spin_unlock(&aa_buffers_lock);
+}
+
 /*
  * AppArmor init functions
  */
@@ -1538,38 +1584,48 @@ static int __init set_init_ctx(void)
 
 static void destroy_buffers(void)
 {
-	u32 i, j;
+	union aa_buffer *aa_buf;
 
-	for_each_possible_cpu(i) {
-		for_each_cpu_buffer(j) {
-			kfree(per_cpu(aa_buffers, i).buf[j]);
-			per_cpu(aa_buffers, i).buf[j] = NULL;
-		}
+	spin_lock(&aa_buffers_lock);
+	while (!list_empty(&aa_global_buffers)) {
+		aa_buf = list_first_entry(&aa_global_buffers, union aa_buffer,
+					 list);
+		list_del(&aa_buf->list);
+		spin_unlock(&aa_buffers_lock);
+		kfree(aa_buf);
+		spin_lock(&aa_buffers_lock);
 	}
+	spin_unlock(&aa_buffers_lock);
 }
 
 static int __init alloc_buffers(void)
 {
-	u32 i, j;
+	union aa_buffer *aa_buf;
+	int i, num;
 
-	for_each_possible_cpu(i) {
-		for_each_cpu_buffer(j) {
-			char *buffer;
+	/*
+	 * A function may require two buffers at once. Usually the buffers are
+	 * used for a short period of time and are shared. On UP kernel buffers
+	 * two should be enough, with more CPUs it is possible that more
+	 * buffers will be used simultaneously. The preallocated pool may grow.
+	 * This preallocation has also the side-effect that AppArmor will be
+	 * disabled early at boot if aa_g_path_max is extremly high.
+	 */
+	if (num_online_cpus() > 1)
+		num = 4;
+	else
+		num = 2;
 
-			if (cpu_to_node(i) > num_online_nodes())
-				/* fallback to kmalloc for offline nodes */
-				buffer = kmalloc(aa_g_path_max, GFP_KERNEL);
-			else
-				buffer = kmalloc_node(aa_g_path_max, GFP_KERNEL,
-						      cpu_to_node(i));
-			if (!buffer) {
-				destroy_buffers();
-				return -ENOMEM;
-			}
-			per_cpu(aa_buffers, i).buf[j] = buffer;
+	for (i = 0; i < num; i++) {
+
+		aa_buf = kmalloc(aa_g_path_max, GFP_KERNEL |
+				 __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
+		if (!aa_buf) {
+			destroy_buffers();
+			return -ENOMEM;
 		}
+		aa_put_buffer(&aa_buf->buffer[0]);
 	}
-
 	return 0;
 }
 
@@ -1734,7 +1790,7 @@ static int __init apparmor_init(void)
 	error = alloc_buffers();
 	if (error) {
 		AA_ERROR("Unable to allocate work buffers\n");
-		goto buffers_out;
+		goto alloc_out;
 	}
 
 	error = set_init_ctx();
@@ -1759,7 +1815,6 @@ static int __init apparmor_init(void)
 
 buffers_out:
 	destroy_buffers();
-
 alloc_out:
 	aa_destroy_aafs();
 	aa_teardown_dfa_engine();
diff --git a/security/apparmor/mount.c b/security/apparmor/mount.c
index 8c3787399356b..267a26fba14e1 100644
--- a/security/apparmor/mount.c
+++ b/security/apparmor/mount.c
@@ -412,11 +412,13 @@ int aa_remount(struct aa_label *label, const struct path *path,
 
 	binary = path->dentry->d_sb->s_type->fs_flags & FS_BINARY_MOUNTDATA;
 
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
+	if (!buffer)
+		return -ENOMEM;
 	error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, NULL, NULL, NULL,
 				  flags, data, binary));
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
@@ -441,11 +443,18 @@ int aa_bind_mount(struct aa_label *label, const struct path *path,
 	if (error)
 		return error;
 
-	get_buffers(buffer, old_buffer);
+	buffer = aa_get_buffer();
+	old_buffer = aa_get_buffer();
+	error = -ENOMEM;
+	if (!buffer || old_buffer)
+		goto out;
+
 	error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, &old_path, old_buffer,
 				  NULL, flags, NULL, false));
-	put_buffers(buffer, old_buffer);
+out:
+	aa_put_buffer(buffer);
+	aa_put_buffer(old_buffer);
 	path_put(&old_path);
 
 	return error;
@@ -465,11 +474,13 @@ int aa_mount_change_type(struct aa_label *label, const struct path *path,
 	flags &= (MS_REC | MS_SILENT | MS_SHARED | MS_PRIVATE | MS_SLAVE |
 		  MS_UNBINDABLE);
 
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
+	if (!buffer)
+		return -ENOMEM;
 	error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, NULL, NULL, NULL,
 				  flags, NULL, false));
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
@@ -492,11 +503,17 @@ int aa_move_mount(struct aa_label *label, const struct path *path,
 	if (error)
 		return error;
 
-	get_buffers(buffer, old_buffer);
+	buffer = aa_get_buffer();
+	old_buffer = aa_get_buffer();
+	error = -ENOMEM;
+	if (!buffer || !old_buffer)
+		goto out;
 	error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, &old_path, old_buffer,
 				  NULL, MS_MOVE, NULL, false));
-	put_buffers(buffer, old_buffer);
+out:
+	aa_put_buffer(buffer);
+	aa_put_buffer(old_buffer);
 	path_put(&old_path);
 
 	return error;
@@ -537,17 +554,29 @@ int aa_new_mount(struct aa_label *label, const char *dev_name,
 		}
 	}
 
-	get_buffers(buffer, dev_buffer);
+	buffer = aa_get_buffer();
+	if (!buffer) {
+		error = -ENOMEM;
+		goto out;
+	}
 	if (dev_path) {
 		error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, dev_path, dev_buffer,
 				  type, flags, data, binary));
 	} else {
+		dev_buffer = aa_get_buffer();
+		if (!dev_buffer) {
+			error = -ENOMEM;
+			goto out;
+		}
 		error = fn_for_each_confined(label, profile,
 			match_mnt_path_str(profile, path, buffer, dev_name,
 					   type, flags, data, binary, NULL));
 	}
-	put_buffers(buffer, dev_buffer);
+
+out:
+	aa_put_buffer(buffer);
+	aa_put_buffer(dev_buffer);
 	if (dev_path)
 		path_put(dev_path);
 
@@ -595,10 +624,13 @@ int aa_umount(struct aa_label *label, struct vfsmount *mnt, int flags)
 	AA_BUG(!label);
 	AA_BUG(!mnt);
 
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
+	if (!buffer)
+		return -ENOMEM;
+
 	error = fn_for_each_confined(label, profile,
 			profile_umount(profile, &path, buffer));
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
@@ -671,7 +703,11 @@ int aa_pivotroot(struct aa_label *label, const struct path *old_path,
 	AA_BUG(!old_path);
 	AA_BUG(!new_path);
 
-	get_buffers(old_buffer, new_buffer);
+	old_buffer = aa_get_buffer();
+	new_buffer = aa_get_buffer();
+	error = -ENOMEM;
+	if (!old_buffer || !new_buffer)
+		goto out;
 	target = fn_label_build(label, profile, GFP_ATOMIC,
 			build_pivotroot(profile, new_path, new_buffer,
 					old_path, old_buffer));
@@ -690,7 +726,8 @@ int aa_pivotroot(struct aa_label *label, const struct path *old_path,
 		/* already audited error */
 		error = PTR_ERR(target);
 out:
-	put_buffers(old_buffer, new_buffer);
+	aa_put_buffer(old_buffer);
+	aa_put_buffer(new_buffer);
 
 	return error;
 
-- 
2.20.1


^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH v3] apparmor: Use a memory pool instead per-CPU caches
  2019-05-03 11:51                 ` [PATCH v3] " Sebastian Andrzej Siewior
@ 2019-05-03 12:41                   ` Tetsuo Handa
  2019-05-03 14:12                     ` [PATCH v4] " Sebastian Andrzej Siewior
  0 siblings, 1 reply; 20+ messages in thread
From: Tetsuo Handa @ 2019-05-03 12:41 UTC (permalink / raw)
  To: Sebastian Andrzej Siewior
  Cc: John Johansen, linux-security-module, James Morris,
	Serge E. Hallyn, tglx

On 2019/05/03 20:51, Sebastian Andrzej Siewior wrote:
> +void aa_put_buffer(char *buf)
> +{
> +	union aa_buffer *aa_buf;
> +

buf == NULL if aa_put_buffer() was called due to aa_get_buffer() == NULL.

> +	aa_buf = container_of(buf, union aa_buffer, buffer[0]);
> +
> +	spin_lock(&aa_buffers_lock);
> +	list_add(&aa_buf->list, &aa_global_buffers);
> +	spin_unlock(&aa_buffers_lock);
> +}
> +
>  /*
>   * AppArmor init functions
>   */

^ permalink raw reply	[flat|nested] 20+ messages in thread

* [PATCH v4] apparmor: Use a memory pool instead per-CPU caches
  2019-05-03 12:41                   ` Tetsuo Handa
@ 2019-05-03 14:12                     ` " Sebastian Andrzej Siewior
  2019-05-07 19:57                       ` John Johansen
  0 siblings, 1 reply; 20+ messages in thread
From: Sebastian Andrzej Siewior @ 2019-05-03 14:12 UTC (permalink / raw)
  To: Tetsuo Handa
  Cc: John Johansen, linux-security-module, James Morris,
	Serge E. Hallyn, tglx

The get_buffers() macro may provide one or two buffers to the caller.
Those buffers are pre-allocated on init for each CPU. By default it
allocates
	2* 2 * MAX_PATH * POSSIBLE_CPU

which equals 64KiB on a system with 4 CPUs or 1MiB with 64 CPUs and so
on.

Replace the per-CPU buffers with a common memory pool which is shared
across all CPUs. The pool grows on demand and never shrinks. The pool
starts with two (UP) or four (SMP) elements. By using this pool it is
possible to request a buffer and keeping preemption enabled which avoids
the hack in profile_transition().

It has been pointed out by Tetsuo Handa that GFP_KERNEL allocations for
small amount of memory do not fail. In order not to have an endless
retry, __GFP_RETRY_MAYFAIL is passed (so the memory allocation is not
repeated until success) and retried once hoping that in the meantime a
buffer has been returned to the pool. Since now NULL is possible all
allocation paths check the buffer pointer and return -ENOMEM on failure.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
v3…v4:
   - let aa_put_buffer() accept a NULL pointer, noticed by Tetsuo Handa

v2…v3:
   - remove an unused flags variable.

v1…v2:
   - Use max_t instead min_t for a minimal buffer.
   - Pre-allocate 2 buffers on UP and 4 buffers on SMP systems.
   - Use __GFP_RETRY_MAYFAIL | __GFP_NOWARN on memory allocation. The
     allocation may fail under pressure and we will retry once.
   - Add an error path to each caller of aa_get_buffer() if the memory
     allocation fails.

 security/apparmor/domain.c       |  24 +++----
 security/apparmor/file.c         |  24 +++++--
 security/apparmor/include/path.h |  49 +-------------
 security/apparmor/lsm.c          | 107 +++++++++++++++++++++++--------
 security/apparmor/mount.c        |  65 +++++++++++++++----
 5 files changed, 161 insertions(+), 108 deletions(-)

diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
index ca2dccf5b445e..cae0e619ff4fe 100644
--- a/security/apparmor/domain.c
+++ b/security/apparmor/domain.c
@@ -689,20 +689,9 @@ static struct aa_label *profile_transition(struct aa_profile *profile,
 	} else if (COMPLAIN_MODE(profile)) {
 		/* no exec permission - learning mode */
 		struct aa_profile *new_profile = NULL;
-		char *n = kstrdup(name, GFP_ATOMIC);
 
-		if (n) {
-			/* name is ptr into buffer */
-			long pos = name - buffer;
-			/* break per cpu buffer hold */
-			put_buffers(buffer);
-			new_profile = aa_new_null_profile(profile, false, n,
-							  GFP_KERNEL);
-			get_buffers(buffer);
-			name = buffer + pos;
-			strcpy((char *)name, n);
-			kfree(n);
-		}
+		new_profile = aa_new_null_profile(profile, false, name,
+						  GFP_KERNEL);
 		if (!new_profile) {
 			error = -ENOMEM;
 			info = "could not create null profile";
@@ -907,7 +896,12 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
 		ctx->nnp = aa_get_label(label);
 
 	/* buffer freed below, name is pointer into buffer */
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
+	if (!buffer) {
+		error = -ENOMEM;
+		goto done;
+	}
+
 	/* Test for onexec first as onexec override other x transitions. */
 	if (ctx->onexec)
 		new = handle_onexec(label, ctx->onexec, ctx->token,
@@ -979,7 +973,7 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
 
 done:
 	aa_put_label(label);
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 
diff --git a/security/apparmor/file.c b/security/apparmor/file.c
index d0afed9ebd0ed..7b424e73a8c74 100644
--- a/security/apparmor/file.c
+++ b/security/apparmor/file.c
@@ -336,12 +336,14 @@ int aa_path_perm(const char *op, struct aa_label *label,
 
 	flags |= PATH_DELEGATE_DELETED | (S_ISDIR(cond->mode) ? PATH_IS_DIR :
 								0);
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
+	if (!buffer)
+		return -ENOMEM;
 	error = fn_for_each_confined(label, profile,
 			profile_path_perm(op, profile, path, buffer, request,
 					  cond, flags, &perms));
 
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
@@ -479,12 +481,18 @@ int aa_path_link(struct aa_label *label, struct dentry *old_dentry,
 	int error;
 
 	/* buffer freed below, lname is pointer in buffer */
-	get_buffers(buffer, buffer2);
+	buffer = aa_get_buffer();
+	buffer2 = aa_get_buffer();
+	error = -ENOMEM;
+	if (!buffer || !buffer2)
+		goto out;
+
 	error = fn_for_each_confined(label, profile,
 			profile_path_link(profile, &link, buffer, &target,
 					  buffer2, &cond));
-	put_buffers(buffer, buffer2);
-
+out:
+	aa_put_buffer(buffer);
+	aa_put_buffer(buffer2);
 	return error;
 }
 
@@ -528,7 +536,9 @@ static int __file_path_perm(const char *op, struct aa_label *label,
 		return 0;
 
 	flags = PATH_DELEGATE_DELETED | (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0);
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
+	if (!buffer)
+		return -ENOMEM;
 
 	/* check every profile in task label not in current cache */
 	error = fn_for_each_not_in_set(flabel, label, profile,
@@ -557,7 +567,7 @@ static int __file_path_perm(const char *op, struct aa_label *label,
 	if (!error)
 		update_file_ctx(file_ctx(file), label, request);
 
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
diff --git a/security/apparmor/include/path.h b/security/apparmor/include/path.h
index b6380c5f00972..b0b2ab85e42d8 100644
--- a/security/apparmor/include/path.h
+++ b/security/apparmor/include/path.h
@@ -15,7 +15,6 @@
 #ifndef __AA_PATH_H
 #define __AA_PATH_H
 
-
 enum path_flags {
 	PATH_IS_DIR = 0x1,		/* path is a directory */
 	PATH_CONNECT_PATH = 0x4,	/* connect disconnected paths to / */
@@ -30,51 +29,7 @@ int aa_path_name(const struct path *path, int flags, char *buffer,
 		 const char **name, const char **info,
 		 const char *disconnected);
 
-#define MAX_PATH_BUFFERS 2
-
-/* Per cpu buffers used during mediation */
-/* preallocated buffers to use during path lookups */
-struct aa_buffers {
-	char *buf[MAX_PATH_BUFFERS];
-};
-
-#include <linux/percpu.h>
-#include <linux/preempt.h>
-
-DECLARE_PER_CPU(struct aa_buffers, aa_buffers);
-
-#define ASSIGN(FN, A, X, N) ((X) = FN(A, N))
-#define EVAL1(FN, A, X) ASSIGN(FN, A, X, 0) /*X = FN(0)*/
-#define EVAL2(FN, A, X, Y...)	\
-	do { ASSIGN(FN, A, X, 1);  EVAL1(FN, A, Y); } while (0)
-#define EVAL(FN, A, X...) CONCATENATE(EVAL, COUNT_ARGS(X))(FN, A, X)
-
-#define for_each_cpu_buffer(I) for ((I) = 0; (I) < MAX_PATH_BUFFERS; (I)++)
-
-#ifdef CONFIG_DEBUG_PREEMPT
-#define AA_BUG_PREEMPT_ENABLED(X) AA_BUG(preempt_count() <= 0, X)
-#else
-#define AA_BUG_PREEMPT_ENABLED(X) /* nop */
-#endif
-
-#define __get_buffer(C, N) ({						\
-	AA_BUG_PREEMPT_ENABLED("__get_buffer without preempt disabled");  \
-	(C)->buf[(N)]; })
-
-#define __get_buffers(C, X...)    EVAL(__get_buffer, C, X)
-
-#define __put_buffers(X, Y...) ((void)&(X))
-
-#define get_buffers(X...)						\
-do {									\
-	struct aa_buffers *__cpu_var = get_cpu_ptr(&aa_buffers);	\
-	__get_buffers(__cpu_var, X);					\
-} while (0)
-
-#define put_buffers(X, Y...)		\
-do {					\
-	__put_buffers(X, Y);		\
-	put_cpu_ptr(&aa_buffers);	\
-} while (0)
+char *aa_get_buffer(void);
+void aa_put_buffer(char *buf);
 
 #endif /* __AA_PATH_H */
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 87500bde5a92d..c5915a6853738 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -47,8 +47,13 @@
 /* Flag indicating whether initialization completed */
 int apparmor_initialized;
 
-DEFINE_PER_CPU(struct aa_buffers, aa_buffers);
+union aa_buffer {
+	struct list_head list;
+	char buffer[1];
+};
 
+static LIST_HEAD(aa_global_buffers);
+static DEFINE_SPINLOCK(aa_buffers_lock);
 
 /*
  * LSM hook functions
@@ -1406,6 +1411,7 @@ static int param_set_aauint(const char *val, const struct kernel_param *kp)
 		return -EPERM;
 
 	error = param_set_uint(val, kp);
+	aa_g_path_max = max_t(uint32_t, aa_g_path_max, sizeof(union aa_buffer));
 	pr_info("AppArmor: buffer size set to %d bytes\n", aa_g_path_max);
 
 	return error;
@@ -1518,6 +1524,48 @@ static int param_set_mode(const char *val, const struct kernel_param *kp)
 	return 0;
 }
 
+char *aa_get_buffer(void)
+{
+	union aa_buffer *aa_buf;
+	bool try_again = true;
+
+retry:
+	spin_lock(&aa_buffers_lock);
+	if (!list_empty(&aa_global_buffers)) {
+		aa_buf = list_first_entry(&aa_global_buffers, union aa_buffer,
+					  list);
+		list_del(&aa_buf->list);
+		spin_unlock(&aa_buffers_lock);
+		return &aa_buf->buffer[0];
+	}
+	spin_unlock(&aa_buffers_lock);
+
+	aa_buf = kmalloc(aa_g_path_max, GFP_KERNEL | __GFP_RETRY_MAYFAIL |
+			 __GFP_NOWARN);
+	if (!aa_buf) {
+		if (try_again) {
+			try_again = false;
+			goto retry;
+		}
+		pr_warn_once("AppArmor: Failed to allocate a memory buffer.\n");
+		return NULL;
+	}
+	return &aa_buf->buffer[0];
+}
+
+void aa_put_buffer(char *buf)
+{
+	union aa_buffer *aa_buf;
+
+	if (!buf)
+		return;
+	aa_buf = container_of(buf, union aa_buffer, buffer[0]);
+
+	spin_lock(&aa_buffers_lock);
+	list_add(&aa_buf->list, &aa_global_buffers);
+	spin_unlock(&aa_buffers_lock);
+}
+
 /*
  * AppArmor init functions
  */
@@ -1538,38 +1586,48 @@ static int __init set_init_ctx(void)
 
 static void destroy_buffers(void)
 {
-	u32 i, j;
+	union aa_buffer *aa_buf;
 
-	for_each_possible_cpu(i) {
-		for_each_cpu_buffer(j) {
-			kfree(per_cpu(aa_buffers, i).buf[j]);
-			per_cpu(aa_buffers, i).buf[j] = NULL;
-		}
+	spin_lock(&aa_buffers_lock);
+	while (!list_empty(&aa_global_buffers)) {
+		aa_buf = list_first_entry(&aa_global_buffers, union aa_buffer,
+					 list);
+		list_del(&aa_buf->list);
+		spin_unlock(&aa_buffers_lock);
+		kfree(aa_buf);
+		spin_lock(&aa_buffers_lock);
 	}
+	spin_unlock(&aa_buffers_lock);
 }
 
 static int __init alloc_buffers(void)
 {
-	u32 i, j;
+	union aa_buffer *aa_buf;
+	int i, num;
 
-	for_each_possible_cpu(i) {
-		for_each_cpu_buffer(j) {
-			char *buffer;
+	/*
+	 * A function may require two buffers at once. Usually the buffers are
+	 * used for a short period of time and are shared. On UP kernel buffers
+	 * two should be enough, with more CPUs it is possible that more
+	 * buffers will be used simultaneously. The preallocated pool may grow.
+	 * This preallocation has also the side-effect that AppArmor will be
+	 * disabled early at boot if aa_g_path_max is extremly high.
+	 */
+	if (num_online_cpus() > 1)
+		num = 4;
+	else
+		num = 2;
 
-			if (cpu_to_node(i) > num_online_nodes())
-				/* fallback to kmalloc for offline nodes */
-				buffer = kmalloc(aa_g_path_max, GFP_KERNEL);
-			else
-				buffer = kmalloc_node(aa_g_path_max, GFP_KERNEL,
-						      cpu_to_node(i));
-			if (!buffer) {
-				destroy_buffers();
-				return -ENOMEM;
-			}
-			per_cpu(aa_buffers, i).buf[j] = buffer;
+	for (i = 0; i < num; i++) {
+
+		aa_buf = kmalloc(aa_g_path_max, GFP_KERNEL |
+				 __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
+		if (!aa_buf) {
+			destroy_buffers();
+			return -ENOMEM;
 		}
+		aa_put_buffer(&aa_buf->buffer[0]);
 	}
-
 	return 0;
 }
 
@@ -1734,7 +1792,7 @@ static int __init apparmor_init(void)
 	error = alloc_buffers();
 	if (error) {
 		AA_ERROR("Unable to allocate work buffers\n");
-		goto buffers_out;
+		goto alloc_out;
 	}
 
 	error = set_init_ctx();
@@ -1759,7 +1817,6 @@ static int __init apparmor_init(void)
 
 buffers_out:
 	destroy_buffers();
-
 alloc_out:
 	aa_destroy_aafs();
 	aa_teardown_dfa_engine();
diff --git a/security/apparmor/mount.c b/security/apparmor/mount.c
index 8c3787399356b..267a26fba14e1 100644
--- a/security/apparmor/mount.c
+++ b/security/apparmor/mount.c
@@ -412,11 +412,13 @@ int aa_remount(struct aa_label *label, const struct path *path,
 
 	binary = path->dentry->d_sb->s_type->fs_flags & FS_BINARY_MOUNTDATA;
 
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
+	if (!buffer)
+		return -ENOMEM;
 	error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, NULL, NULL, NULL,
 				  flags, data, binary));
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
@@ -441,11 +443,18 @@ int aa_bind_mount(struct aa_label *label, const struct path *path,
 	if (error)
 		return error;
 
-	get_buffers(buffer, old_buffer);
+	buffer = aa_get_buffer();
+	old_buffer = aa_get_buffer();
+	error = -ENOMEM;
+	if (!buffer || old_buffer)
+		goto out;
+
 	error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, &old_path, old_buffer,
 				  NULL, flags, NULL, false));
-	put_buffers(buffer, old_buffer);
+out:
+	aa_put_buffer(buffer);
+	aa_put_buffer(old_buffer);
 	path_put(&old_path);
 
 	return error;
@@ -465,11 +474,13 @@ int aa_mount_change_type(struct aa_label *label, const struct path *path,
 	flags &= (MS_REC | MS_SILENT | MS_SHARED | MS_PRIVATE | MS_SLAVE |
 		  MS_UNBINDABLE);
 
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
+	if (!buffer)
+		return -ENOMEM;
 	error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, NULL, NULL, NULL,
 				  flags, NULL, false));
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
@@ -492,11 +503,17 @@ int aa_move_mount(struct aa_label *label, const struct path *path,
 	if (error)
 		return error;
 
-	get_buffers(buffer, old_buffer);
+	buffer = aa_get_buffer();
+	old_buffer = aa_get_buffer();
+	error = -ENOMEM;
+	if (!buffer || !old_buffer)
+		goto out;
 	error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, &old_path, old_buffer,
 				  NULL, MS_MOVE, NULL, false));
-	put_buffers(buffer, old_buffer);
+out:
+	aa_put_buffer(buffer);
+	aa_put_buffer(old_buffer);
 	path_put(&old_path);
 
 	return error;
@@ -537,17 +554,29 @@ int aa_new_mount(struct aa_label *label, const char *dev_name,
 		}
 	}
 
-	get_buffers(buffer, dev_buffer);
+	buffer = aa_get_buffer();
+	if (!buffer) {
+		error = -ENOMEM;
+		goto out;
+	}
 	if (dev_path) {
 		error = fn_for_each_confined(label, profile,
 			match_mnt(profile, path, buffer, dev_path, dev_buffer,
 				  type, flags, data, binary));
 	} else {
+		dev_buffer = aa_get_buffer();
+		if (!dev_buffer) {
+			error = -ENOMEM;
+			goto out;
+		}
 		error = fn_for_each_confined(label, profile,
 			match_mnt_path_str(profile, path, buffer, dev_name,
 					   type, flags, data, binary, NULL));
 	}
-	put_buffers(buffer, dev_buffer);
+
+out:
+	aa_put_buffer(buffer);
+	aa_put_buffer(dev_buffer);
 	if (dev_path)
 		path_put(dev_path);
 
@@ -595,10 +624,13 @@ int aa_umount(struct aa_label *label, struct vfsmount *mnt, int flags)
 	AA_BUG(!label);
 	AA_BUG(!mnt);
 
-	get_buffers(buffer);
+	buffer = aa_get_buffer();
+	if (!buffer)
+		return -ENOMEM;
+
 	error = fn_for_each_confined(label, profile,
 			profile_umount(profile, &path, buffer));
-	put_buffers(buffer);
+	aa_put_buffer(buffer);
 
 	return error;
 }
@@ -671,7 +703,11 @@ int aa_pivotroot(struct aa_label *label, const struct path *old_path,
 	AA_BUG(!old_path);
 	AA_BUG(!new_path);
 
-	get_buffers(old_buffer, new_buffer);
+	old_buffer = aa_get_buffer();
+	new_buffer = aa_get_buffer();
+	error = -ENOMEM;
+	if (!old_buffer || !new_buffer)
+		goto out;
 	target = fn_label_build(label, profile, GFP_ATOMIC,
 			build_pivotroot(profile, new_path, new_buffer,
 					old_path, old_buffer));
@@ -690,7 +726,8 @@ int aa_pivotroot(struct aa_label *label, const struct path *old_path,
 		/* already audited error */
 		error = PTR_ERR(target);
 out:
-	put_buffers(old_buffer, new_buffer);
+	aa_put_buffer(old_buffer);
+	aa_put_buffer(new_buffer);
 
 	return error;
 
-- 
2.20.1


^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH v4] apparmor: Use a memory pool instead per-CPU caches
  2019-05-03 14:12                     ` [PATCH v4] " Sebastian Andrzej Siewior
@ 2019-05-07 19:57                       ` John Johansen
  2019-10-02  8:59                         ` Sebastian Andrzej Siewior
  0 siblings, 1 reply; 20+ messages in thread
From: John Johansen @ 2019-05-07 19:57 UTC (permalink / raw)
  To: Sebastian Andrzej Siewior, Tetsuo Handa
  Cc: linux-security-module, James Morris, Serge E. Hallyn, tglx

On 5/3/19 7:12 AM, Sebastian Andrzej Siewior wrote:
> The get_buffers() macro may provide one or two buffers to the caller.
> Those buffers are pre-allocated on init for each CPU. By default it
> allocates
> 	2* 2 * MAX_PATH * POSSIBLE_CPU
> 
> which equals 64KiB on a system with 4 CPUs or 1MiB with 64 CPUs and so
> on.
> 
> Replace the per-CPU buffers with a common memory pool which is shared
> across all CPUs. The pool grows on demand and never shrinks. The pool
> starts with two (UP) or four (SMP) elements. By using this pool it is
> possible to request a buffer and keeping preemption enabled which avoids
> the hack in profile_transition().
> 
> It has been pointed out by Tetsuo Handa that GFP_KERNEL allocations for
> small amount of memory do not fail. In order not to have an endless
> retry, __GFP_RETRY_MAYFAIL is passed (so the memory allocation is not
> repeated until success) and retried once hoping that in the meantime a
> buffer has been returned to the pool. Since now NULL is possible all
> allocation paths check the buffer pointer and return -ENOMEM on failure.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

I am going to pull this into my tree and let it sit in linux-next
for a cycle so we can get better testing on this before it is pushed
out


> ---
> v3…v4:
>    - let aa_put_buffer() accept a NULL pointer, noticed by Tetsuo Handa
> 
> v2…v3:
>    - remove an unused flags variable.
> 
> v1…v2:
>    - Use max_t instead min_t for a minimal buffer.
>    - Pre-allocate 2 buffers on UP and 4 buffers on SMP systems.
>    - Use __GFP_RETRY_MAYFAIL | __GFP_NOWARN on memory allocation. The
>      allocation may fail under pressure and we will retry once.
>    - Add an error path to each caller of aa_get_buffer() if the memory
>      allocation fails.
> 
>  security/apparmor/domain.c       |  24 +++----
>  security/apparmor/file.c         |  24 +++++--
>  security/apparmor/include/path.h |  49 +-------------
>  security/apparmor/lsm.c          | 107 +++++++++++++++++++++++--------
>  security/apparmor/mount.c        |  65 +++++++++++++++----
>  5 files changed, 161 insertions(+), 108 deletions(-)
> 
> diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
> index ca2dccf5b445e..cae0e619ff4fe 100644
> --- a/security/apparmor/domain.c
> +++ b/security/apparmor/domain.c
> @@ -689,20 +689,9 @@ static struct aa_label *profile_transition(struct aa_profile *profile,
>  	} else if (COMPLAIN_MODE(profile)) {
>  		/* no exec permission - learning mode */
>  		struct aa_profile *new_profile = NULL;
> -		char *n = kstrdup(name, GFP_ATOMIC);
>  
> -		if (n) {
> -			/* name is ptr into buffer */
> -			long pos = name - buffer;
> -			/* break per cpu buffer hold */
> -			put_buffers(buffer);
> -			new_profile = aa_new_null_profile(profile, false, n,
> -							  GFP_KERNEL);
> -			get_buffers(buffer);
> -			name = buffer + pos;
> -			strcpy((char *)name, n);
> -			kfree(n);
> -		}
> +		new_profile = aa_new_null_profile(profile, false, name,
> +						  GFP_KERNEL);
>  		if (!new_profile) {
>  			error = -ENOMEM;
>  			info = "could not create null profile";
> @@ -907,7 +896,12 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
>  		ctx->nnp = aa_get_label(label);
>  
>  	/* buffer freed below, name is pointer into buffer */
> -	get_buffers(buffer);
> +	buffer = aa_get_buffer();
> +	if (!buffer) {
> +		error = -ENOMEM;
> +		goto done;
> +	}
> +
>  	/* Test for onexec first as onexec override other x transitions. */
>  	if (ctx->onexec)
>  		new = handle_onexec(label, ctx->onexec, ctx->token,
> @@ -979,7 +973,7 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
>  
>  done:
>  	aa_put_label(label);
> -	put_buffers(buffer);
> +	aa_put_buffer(buffer);
>  
>  	return error;
>  
> diff --git a/security/apparmor/file.c b/security/apparmor/file.c
> index d0afed9ebd0ed..7b424e73a8c74 100644
> --- a/security/apparmor/file.c
> +++ b/security/apparmor/file.c
> @@ -336,12 +336,14 @@ int aa_path_perm(const char *op, struct aa_label *label,
>  
>  	flags |= PATH_DELEGATE_DELETED | (S_ISDIR(cond->mode) ? PATH_IS_DIR :
>  								0);
> -	get_buffers(buffer);
> +	buffer = aa_get_buffer();
> +	if (!buffer)
> +		return -ENOMEM;
>  	error = fn_for_each_confined(label, profile,
>  			profile_path_perm(op, profile, path, buffer, request,
>  					  cond, flags, &perms));
>  
> -	put_buffers(buffer);
> +	aa_put_buffer(buffer);
>  
>  	return error;
>  }
> @@ -479,12 +481,18 @@ int aa_path_link(struct aa_label *label, struct dentry *old_dentry,
>  	int error;
>  
>  	/* buffer freed below, lname is pointer in buffer */
> -	get_buffers(buffer, buffer2);
> +	buffer = aa_get_buffer();
> +	buffer2 = aa_get_buffer();
> +	error = -ENOMEM;
> +	if (!buffer || !buffer2)
> +		goto out;
> +
>  	error = fn_for_each_confined(label, profile,
>  			profile_path_link(profile, &link, buffer, &target,
>  					  buffer2, &cond));
> -	put_buffers(buffer, buffer2);
> -
> +out:
> +	aa_put_buffer(buffer);
> +	aa_put_buffer(buffer2);
>  	return error;
>  }
>  
> @@ -528,7 +536,9 @@ static int __file_path_perm(const char *op, struct aa_label *label,
>  		return 0;
>  
>  	flags = PATH_DELEGATE_DELETED | (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0);
> -	get_buffers(buffer);
> +	buffer = aa_get_buffer();
> +	if (!buffer)
> +		return -ENOMEM;
>  
>  	/* check every profile in task label not in current cache */
>  	error = fn_for_each_not_in_set(flabel, label, profile,
> @@ -557,7 +567,7 @@ static int __file_path_perm(const char *op, struct aa_label *label,
>  	if (!error)
>  		update_file_ctx(file_ctx(file), label, request);
>  
> -	put_buffers(buffer);
> +	aa_put_buffer(buffer);
>  
>  	return error;
>  }
> diff --git a/security/apparmor/include/path.h b/security/apparmor/include/path.h
> index b6380c5f00972..b0b2ab85e42d8 100644
> --- a/security/apparmor/include/path.h
> +++ b/security/apparmor/include/path.h
> @@ -15,7 +15,6 @@
>  #ifndef __AA_PATH_H
>  #define __AA_PATH_H
>  
> -
>  enum path_flags {
>  	PATH_IS_DIR = 0x1,		/* path is a directory */
>  	PATH_CONNECT_PATH = 0x4,	/* connect disconnected paths to / */
> @@ -30,51 +29,7 @@ int aa_path_name(const struct path *path, int flags, char *buffer,
>  		 const char **name, const char **info,
>  		 const char *disconnected);
>  
> -#define MAX_PATH_BUFFERS 2
> -
> -/* Per cpu buffers used during mediation */
> -/* preallocated buffers to use during path lookups */
> -struct aa_buffers {
> -	char *buf[MAX_PATH_BUFFERS];
> -};
> -
> -#include <linux/percpu.h>
> -#include <linux/preempt.h>
> -
> -DECLARE_PER_CPU(struct aa_buffers, aa_buffers);
> -
> -#define ASSIGN(FN, A, X, N) ((X) = FN(A, N))
> -#define EVAL1(FN, A, X) ASSIGN(FN, A, X, 0) /*X = FN(0)*/
> -#define EVAL2(FN, A, X, Y...)	\
> -	do { ASSIGN(FN, A, X, 1);  EVAL1(FN, A, Y); } while (0)
> -#define EVAL(FN, A, X...) CONCATENATE(EVAL, COUNT_ARGS(X))(FN, A, X)
> -
> -#define for_each_cpu_buffer(I) for ((I) = 0; (I) < MAX_PATH_BUFFERS; (I)++)
> -
> -#ifdef CONFIG_DEBUG_PREEMPT
> -#define AA_BUG_PREEMPT_ENABLED(X) AA_BUG(preempt_count() <= 0, X)
> -#else
> -#define AA_BUG_PREEMPT_ENABLED(X) /* nop */
> -#endif
> -
> -#define __get_buffer(C, N) ({						\
> -	AA_BUG_PREEMPT_ENABLED("__get_buffer without preempt disabled");  \
> -	(C)->buf[(N)]; })
> -
> -#define __get_buffers(C, X...)    EVAL(__get_buffer, C, X)
> -
> -#define __put_buffers(X, Y...) ((void)&(X))
> -
> -#define get_buffers(X...)						\
> -do {									\
> -	struct aa_buffers *__cpu_var = get_cpu_ptr(&aa_buffers);	\
> -	__get_buffers(__cpu_var, X);					\
> -} while (0)
> -
> -#define put_buffers(X, Y...)		\
> -do {					\
> -	__put_buffers(X, Y);		\
> -	put_cpu_ptr(&aa_buffers);	\
> -} while (0)
> +char *aa_get_buffer(void);
> +void aa_put_buffer(char *buf);
>  
>  #endif /* __AA_PATH_H */
> diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
> index 87500bde5a92d..c5915a6853738 100644
> --- a/security/apparmor/lsm.c
> +++ b/security/apparmor/lsm.c
> @@ -47,8 +47,13 @@
>  /* Flag indicating whether initialization completed */
>  int apparmor_initialized;
>  
> -DEFINE_PER_CPU(struct aa_buffers, aa_buffers);
> +union aa_buffer {
> +	struct list_head list;
> +	char buffer[1];
> +};
>  
> +static LIST_HEAD(aa_global_buffers);
> +static DEFINE_SPINLOCK(aa_buffers_lock);
>  
>  /*
>   * LSM hook functions
> @@ -1406,6 +1411,7 @@ static int param_set_aauint(const char *val, const struct kernel_param *kp)
>  		return -EPERM;
>  
>  	error = param_set_uint(val, kp);
> +	aa_g_path_max = max_t(uint32_t, aa_g_path_max, sizeof(union aa_buffer));
>  	pr_info("AppArmor: buffer size set to %d bytes\n", aa_g_path_max);
>  
>  	return error;
> @@ -1518,6 +1524,48 @@ static int param_set_mode(const char *val, const struct kernel_param *kp)
>  	return 0;
>  }
>  
> +char *aa_get_buffer(void)
> +{
> +	union aa_buffer *aa_buf;
> +	bool try_again = true;
> +
> +retry:
> +	spin_lock(&aa_buffers_lock);
> +	if (!list_empty(&aa_global_buffers)) {
> +		aa_buf = list_first_entry(&aa_global_buffers, union aa_buffer,
> +					  list);
> +		list_del(&aa_buf->list);
> +		spin_unlock(&aa_buffers_lock);
> +		return &aa_buf->buffer[0];
> +	}
> +	spin_unlock(&aa_buffers_lock);
> +
> +	aa_buf = kmalloc(aa_g_path_max, GFP_KERNEL | __GFP_RETRY_MAYFAIL |
> +			 __GFP_NOWARN);
> +	if (!aa_buf) {
> +		if (try_again) {
> +			try_again = false;
> +			goto retry;
> +		}
> +		pr_warn_once("AppArmor: Failed to allocate a memory buffer.\n");
> +		return NULL;
> +	}
> +	return &aa_buf->buffer[0];
> +}
> +
> +void aa_put_buffer(char *buf)
> +{
> +	union aa_buffer *aa_buf;
> +
> +	if (!buf)
> +		return;
> +	aa_buf = container_of(buf, union aa_buffer, buffer[0]);
> +
> +	spin_lock(&aa_buffers_lock);
> +	list_add(&aa_buf->list, &aa_global_buffers);
> +	spin_unlock(&aa_buffers_lock);
> +}
> +
>  /*
>   * AppArmor init functions
>   */
> @@ -1538,38 +1586,48 @@ static int __init set_init_ctx(void)
>  
>  static void destroy_buffers(void)
>  {
> -	u32 i, j;
> +	union aa_buffer *aa_buf;
>  
> -	for_each_possible_cpu(i) {
> -		for_each_cpu_buffer(j) {
> -			kfree(per_cpu(aa_buffers, i).buf[j]);
> -			per_cpu(aa_buffers, i).buf[j] = NULL;
> -		}
> +	spin_lock(&aa_buffers_lock);
> +	while (!list_empty(&aa_global_buffers)) {
> +		aa_buf = list_first_entry(&aa_global_buffers, union aa_buffer,
> +					 list);
> +		list_del(&aa_buf->list);
> +		spin_unlock(&aa_buffers_lock);
> +		kfree(aa_buf);
> +		spin_lock(&aa_buffers_lock);
>  	}
> +	spin_unlock(&aa_buffers_lock);
>  }
>  
>  static int __init alloc_buffers(void)
>  {
> -	u32 i, j;
> +	union aa_buffer *aa_buf;
> +	int i, num;
>  
> -	for_each_possible_cpu(i) {
> -		for_each_cpu_buffer(j) {
> -			char *buffer;
> +	/*
> +	 * A function may require two buffers at once. Usually the buffers are
> +	 * used for a short period of time and are shared. On UP kernel buffers
> +	 * two should be enough, with more CPUs it is possible that more
> +	 * buffers will be used simultaneously. The preallocated pool may grow.
> +	 * This preallocation has also the side-effect that AppArmor will be
> +	 * disabled early at boot if aa_g_path_max is extremly high.
> +	 */
> +	if (num_online_cpus() > 1)
> +		num = 4;
> +	else
> +		num = 2;
>  
> -			if (cpu_to_node(i) > num_online_nodes())
> -				/* fallback to kmalloc for offline nodes */
> -				buffer = kmalloc(aa_g_path_max, GFP_KERNEL);
> -			else
> -				buffer = kmalloc_node(aa_g_path_max, GFP_KERNEL,
> -						      cpu_to_node(i));
> -			if (!buffer) {
> -				destroy_buffers();
> -				return -ENOMEM;
> -			}
> -			per_cpu(aa_buffers, i).buf[j] = buffer;
> +	for (i = 0; i < num; i++) {
> +
> +		aa_buf = kmalloc(aa_g_path_max, GFP_KERNEL |
> +				 __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
> +		if (!aa_buf) {
> +			destroy_buffers();
> +			return -ENOMEM;
>  		}
> +		aa_put_buffer(&aa_buf->buffer[0]);
>  	}
> -
>  	return 0;
>  }
>  
> @@ -1734,7 +1792,7 @@ static int __init apparmor_init(void)
>  	error = alloc_buffers();
>  	if (error) {
>  		AA_ERROR("Unable to allocate work buffers\n");
> -		goto buffers_out;
> +		goto alloc_out;
>  	}
>  
>  	error = set_init_ctx();
> @@ -1759,7 +1817,6 @@ static int __init apparmor_init(void)
>  
>  buffers_out:
>  	destroy_buffers();
> -
>  alloc_out:
>  	aa_destroy_aafs();
>  	aa_teardown_dfa_engine();
> diff --git a/security/apparmor/mount.c b/security/apparmor/mount.c
> index 8c3787399356b..267a26fba14e1 100644
> --- a/security/apparmor/mount.c
> +++ b/security/apparmor/mount.c
> @@ -412,11 +412,13 @@ int aa_remount(struct aa_label *label, const struct path *path,
>  
>  	binary = path->dentry->d_sb->s_type->fs_flags & FS_BINARY_MOUNTDATA;
>  
> -	get_buffers(buffer);
> +	buffer = aa_get_buffer();
> +	if (!buffer)
> +		return -ENOMEM;
>  	error = fn_for_each_confined(label, profile,
>  			match_mnt(profile, path, buffer, NULL, NULL, NULL,
>  				  flags, data, binary));
> -	put_buffers(buffer);
> +	aa_put_buffer(buffer);
>  
>  	return error;
>  }
> @@ -441,11 +443,18 @@ int aa_bind_mount(struct aa_label *label, const struct path *path,
>  	if (error)
>  		return error;
>  
> -	get_buffers(buffer, old_buffer);
> +	buffer = aa_get_buffer();
> +	old_buffer = aa_get_buffer();
> +	error = -ENOMEM;
> +	if (!buffer || old_buffer)
> +		goto out;
> +
>  	error = fn_for_each_confined(label, profile,
>  			match_mnt(profile, path, buffer, &old_path, old_buffer,
>  				  NULL, flags, NULL, false));
> -	put_buffers(buffer, old_buffer);
> +out:
> +	aa_put_buffer(buffer);
> +	aa_put_buffer(old_buffer);
>  	path_put(&old_path);
>  
>  	return error;
> @@ -465,11 +474,13 @@ int aa_mount_change_type(struct aa_label *label, const struct path *path,
>  	flags &= (MS_REC | MS_SILENT | MS_SHARED | MS_PRIVATE | MS_SLAVE |
>  		  MS_UNBINDABLE);
>  
> -	get_buffers(buffer);
> +	buffer = aa_get_buffer();
> +	if (!buffer)
> +		return -ENOMEM;
>  	error = fn_for_each_confined(label, profile,
>  			match_mnt(profile, path, buffer, NULL, NULL, NULL,
>  				  flags, NULL, false));
> -	put_buffers(buffer);
> +	aa_put_buffer(buffer);
>  
>  	return error;
>  }
> @@ -492,11 +503,17 @@ int aa_move_mount(struct aa_label *label, const struct path *path,
>  	if (error)
>  		return error;
>  
> -	get_buffers(buffer, old_buffer);
> +	buffer = aa_get_buffer();
> +	old_buffer = aa_get_buffer();
> +	error = -ENOMEM;
> +	if (!buffer || !old_buffer)
> +		goto out;
>  	error = fn_for_each_confined(label, profile,
>  			match_mnt(profile, path, buffer, &old_path, old_buffer,
>  				  NULL, MS_MOVE, NULL, false));
> -	put_buffers(buffer, old_buffer);
> +out:
> +	aa_put_buffer(buffer);
> +	aa_put_buffer(old_buffer);
>  	path_put(&old_path);
>  
>  	return error;
> @@ -537,17 +554,29 @@ int aa_new_mount(struct aa_label *label, const char *dev_name,
>  		}
>  	}
>  
> -	get_buffers(buffer, dev_buffer);
> +	buffer = aa_get_buffer();
> +	if (!buffer) {
> +		error = -ENOMEM;
> +		goto out;
> +	}
>  	if (dev_path) {
>  		error = fn_for_each_confined(label, profile,
>  			match_mnt(profile, path, buffer, dev_path, dev_buffer,
>  				  type, flags, data, binary));
>  	} else {
> +		dev_buffer = aa_get_buffer();
> +		if (!dev_buffer) {
> +			error = -ENOMEM;
> +			goto out;
> +		}
>  		error = fn_for_each_confined(label, profile,
>  			match_mnt_path_str(profile, path, buffer, dev_name,
>  					   type, flags, data, binary, NULL));
>  	}
> -	put_buffers(buffer, dev_buffer);
> +
> +out:
> +	aa_put_buffer(buffer);
> +	aa_put_buffer(dev_buffer);
>  	if (dev_path)
>  		path_put(dev_path);
>  
> @@ -595,10 +624,13 @@ int aa_umount(struct aa_label *label, struct vfsmount *mnt, int flags)
>  	AA_BUG(!label);
>  	AA_BUG(!mnt);
>  
> -	get_buffers(buffer);
> +	buffer = aa_get_buffer();
> +	if (!buffer)
> +		return -ENOMEM;
> +
>  	error = fn_for_each_confined(label, profile,
>  			profile_umount(profile, &path, buffer));
> -	put_buffers(buffer);
> +	aa_put_buffer(buffer);
>  
>  	return error;
>  }
> @@ -671,7 +703,11 @@ int aa_pivotroot(struct aa_label *label, const struct path *old_path,
>  	AA_BUG(!old_path);
>  	AA_BUG(!new_path);
>  
> -	get_buffers(old_buffer, new_buffer);
> +	old_buffer = aa_get_buffer();
> +	new_buffer = aa_get_buffer();
> +	error = -ENOMEM;
> +	if (!old_buffer || !new_buffer)
> +		goto out;
>  	target = fn_label_build(label, profile, GFP_ATOMIC,
>  			build_pivotroot(profile, new_path, new_buffer,
>  					old_path, old_buffer));
> @@ -690,7 +726,8 @@ int aa_pivotroot(struct aa_label *label, const struct path *old_path,
>  		/* already audited error */
>  		error = PTR_ERR(target);
>  out:
> -	put_buffers(old_buffer, new_buffer);
> +	aa_put_buffer(old_buffer);
> +	aa_put_buffer(new_buffer);
>  
>  	return error;
>  
> 


^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH 2/2] apparmor: Switch to GFP_KERNEL where possible
  2019-04-05 13:34 ` [PATCH 2/2] apparmor: Switch to GFP_KERNEL where possible Sebastian Andrzej Siewior
@ 2019-05-07 19:57   ` John Johansen
  0 siblings, 0 replies; 20+ messages in thread
From: John Johansen @ 2019-05-07 19:57 UTC (permalink / raw)
  To: Sebastian Andrzej Siewior, linux-security-module
  Cc: James Morris, Serge E. Hallyn, tglx

On 4/5/19 6:34 AM, Sebastian Andrzej Siewior wrote:
> After removing preempt_disable() from get_buffers() it is possible to
> replace a few GFP_ATOMIC allocations with GFP_KERNEL.
> 
> Replace GFP_ATOMIC allocations with GFP_KERNEL where the context looks
> to bee preepmtible.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

I am pulling this one is as well


> ---
>  security/apparmor/domain.c | 20 ++++++++++----------
>  security/apparmor/file.c   |  2 +-
>  security/apparmor/mount.c  |  2 +-
>  3 files changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
> index 1f4a6e420b6d3..b8114d9988bac 100644
> --- a/security/apparmor/domain.c
> +++ b/security/apparmor/domain.c
> @@ -524,7 +524,7 @@ struct aa_label *x_table_lookup(struct aa_profile *profile, u32 xindex,
>  				label = &new_profile->label;
>  			continue;
>  		}
> -		label = aa_label_parse(&profile->label, *name, GFP_ATOMIC,
> +		label = aa_label_parse(&profile->label, *name, GFP_KERNEL,
>  				       true, false);
>  		if (IS_ERR(label))
>  			label = NULL;
> @@ -604,7 +604,7 @@ static struct aa_label *x_to_label(struct aa_profile *profile,
>  		/* base the stack on post domain transition */
>  		struct aa_label *base = new;
>  
> -		new = aa_label_parse(base, stack, GFP_ATOMIC, true, false);
> +		new = aa_label_parse(base, stack, GFP_KERNEL, true, false);
>  		if (IS_ERR(new))
>  			new = NULL;
>  		aa_put_label(base);
> @@ -712,7 +712,7 @@ static struct aa_label *profile_transition(struct aa_profile *profile,
>  		if (DEBUG_ON) {
>  			dbg_printk("apparmor: scrubbing environment variables"
>  				   " for %s profile=", name);
> -			aa_label_printk(new, GFP_ATOMIC);
> +			aa_label_printk(new, GFP_KERNEL);
>  			dbg_printk("\n");
>  		}
>  		*secure_exec = true;
> @@ -788,7 +788,7 @@ static int profile_onexec(struct aa_profile *profile, struct aa_label *onexec,
>  		if (DEBUG_ON) {
>  			dbg_printk("apparmor: scrubbing environment "
>  				   "variables for %s label=", xname);
> -			aa_label_printk(onexec, GFP_ATOMIC);
> +			aa_label_printk(onexec, GFP_KERNEL);
>  			dbg_printk("\n");
>  		}
>  		*secure_exec = true;
> @@ -822,7 +822,7 @@ static struct aa_label *handle_onexec(struct aa_label *label,
>  					       bprm, buffer, cond, unsafe));
>  		if (error)
>  			return ERR_PTR(error);
> -		new = fn_label_build_in_ns(label, profile, GFP_ATOMIC,
> +		new = fn_label_build_in_ns(label, profile, GFP_KERNEL,
>  				aa_get_newest_label(onexec),
>  				profile_transition(profile, bprm, buffer,
>  						   cond, unsafe));
> @@ -834,9 +834,9 @@ static struct aa_label *handle_onexec(struct aa_label *label,
>  					       buffer, cond, unsafe));
>  		if (error)
>  			return ERR_PTR(error);
> -		new = fn_label_build_in_ns(label, profile, GFP_ATOMIC,
> +		new = fn_label_build_in_ns(label, profile, GFP_KERNEL,
>  				aa_label_merge(&profile->label, onexec,
> -					       GFP_ATOMIC),
> +					       GFP_KERNEL),
>  				profile_transition(profile, bprm, buffer,
>  						   cond, unsafe));
>  	}
> @@ -902,7 +902,7 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
>  		new = handle_onexec(label, ctx->onexec, ctx->token,
>  				    bprm, buffer, &cond, &unsafe);
>  	else
> -		new = fn_label_build(label, profile, GFP_ATOMIC,
> +		new = fn_label_build(label, profile, GFP_KERNEL,
>  				profile_transition(profile, bprm, buffer,
>  						   &cond, &unsafe));
>  
> @@ -946,7 +946,7 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
>  		if (DEBUG_ON) {
>  			dbg_printk("scrubbing environment variables for %s "
>  				   "label=", bprm->filename);
> -			aa_label_printk(new, GFP_ATOMIC);
> +			aa_label_printk(new, GFP_KERNEL);
>  			dbg_printk("\n");
>  		}
>  		bprm->secureexec = 1;
> @@ -957,7 +957,7 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
>  		if (DEBUG_ON) {
>  			dbg_printk("apparmor: clearing unsafe personality "
>  				   "bits. %s label=", bprm->filename);
> -			aa_label_printk(new, GFP_ATOMIC);
> +			aa_label_printk(new, GFP_KERNEL);
>  			dbg_printk("\n");
>  		}
>  		bprm->per_clear |= PER_CLEAR_ON_SETID;
> diff --git a/security/apparmor/file.c b/security/apparmor/file.c
> index e422a3f59e80c..3eb2c5369711c 100644
> --- a/security/apparmor/file.c
> +++ b/security/apparmor/file.c
> @@ -80,7 +80,7 @@ static void file_audit_cb(struct audit_buffer *ab, void *va)
>  	if (aad(sa)->peer) {
>  		audit_log_format(ab, " target=");
>  		aa_label_xaudit(ab, labels_ns(aad(sa)->label), aad(sa)->peer,
> -				FLAG_VIEW_SUBNS, GFP_ATOMIC);
> +				FLAG_VIEW_SUBNS, GFP_KERNEL);
>  	} else if (aad(sa)->fs.target) {
>  		audit_log_format(ab, " target=");
>  		audit_log_untrustedstring(ab, aad(sa)->fs.target);
> diff --git a/security/apparmor/mount.c b/security/apparmor/mount.c
> index 8a6cf1c14e82a..d73bc3ceaf9f5 100644
> --- a/security/apparmor/mount.c
> +++ b/security/apparmor/mount.c
> @@ -679,7 +679,7 @@ int aa_pivotroot(struct aa_label *label, const struct path *old_path,
>  
>  	old_buffer = aa_get_buffer();
>  	new_buffer = aa_get_buffer();
> -	target = fn_label_build(label, profile, GFP_ATOMIC,
> +	target = fn_label_build(label, profile, GFP_KERNEL,
>  			build_pivotroot(profile, new_path, new_buffer,
>  					old_path, old_buffer));
>  	if (!target) {
> 


^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH v4] apparmor: Use a memory pool instead per-CPU caches
  2019-05-07 19:57                       ` John Johansen
@ 2019-10-02  8:59                         ` Sebastian Andrzej Siewior
  2019-10-02 15:47                           ` John Johansen
  0 siblings, 1 reply; 20+ messages in thread
From: Sebastian Andrzej Siewior @ 2019-10-02  8:59 UTC (permalink / raw)
  To: John Johansen
  Cc: Tetsuo Handa, linux-security-module, James Morris, Serge E. Hallyn, tglx

On 2019-05-07 12:57:04 [-0700], John Johansen wrote:
> I am going to pull this into my tree and let it sit in linux-next
> for a cycle so we can get better testing on this before it is pushed
> out

We talked about this during the merge window for 5.2-rc1. These changes
were not part of 5.4-rc1. Was there a fallout, anything I can help with?

Sebastian

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH v4] apparmor: Use a memory pool instead per-CPU caches
  2019-10-02  8:59                         ` Sebastian Andrzej Siewior
@ 2019-10-02 15:47                           ` John Johansen
  2019-10-02 15:52                             ` Sebastian Andrzej Siewior
  0 siblings, 1 reply; 20+ messages in thread
From: John Johansen @ 2019-10-02 15:47 UTC (permalink / raw)
  To: Sebastian Andrzej Siewior
  Cc: Tetsuo Handa, linux-security-module, James Morris, Serge E. Hallyn, tglx

On 10/2/19 1:59 AM, Sebastian Andrzej Siewior wrote:
> On 2019-05-07 12:57:04 [-0700], John Johansen wrote:
>> I am going to pull this into my tree and let it sit in linux-next
>> for a cycle so we can get better testing on this before it is pushed
>> out
> 
> We talked about this during the merge window for 5.2-rc1. These changes
> were not part of 5.4-rc1. Was there a fallout, anything I can help with?
> 
I have some patches that are required on top of them. I didn't chase down
all the issues/get the patches done until after -rc6 so everything waits
for the next cycle. I am going to update apparmor-next with the new stack
this week.

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH v4] apparmor: Use a memory pool instead per-CPU caches
  2019-10-02 15:47                           ` John Johansen
@ 2019-10-02 15:52                             ` Sebastian Andrzej Siewior
  0 siblings, 0 replies; 20+ messages in thread
From: Sebastian Andrzej Siewior @ 2019-10-02 15:52 UTC (permalink / raw)
  To: John Johansen
  Cc: Tetsuo Handa, linux-security-module, James Morris, Serge E. Hallyn, tglx

On 2019-10-02 08:47:58 [-0700], John Johansen wrote:
> I have some patches that are required on top of them. I didn't chase down
> all the issues/get the patches done until after -rc6 so everything waits
> for the next cycle. I am going to update apparmor-next with the new stack
> this week.

Okay, thanks for the update.

Sebastian

^ permalink raw reply	[flat|nested] 20+ messages in thread

end of thread, back to index

Thread overview: 20+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-04-05 13:34 [PATCH 1/2] apparmor: Use a memory pool instead per-CPU caches Sebastian Andrzej Siewior
2019-04-05 13:34 ` [PATCH 2/2] apparmor: Switch to GFP_KERNEL where possible Sebastian Andrzej Siewior
2019-05-07 19:57   ` John Johansen
2019-04-15 10:50 ` [PATCH 1/2] apparmor: Use a memory pool instead per-CPU caches Sebastian Andrzej Siewior
2019-04-28 23:56 ` John Johansen
2019-04-30 14:47   ` Sebastian Andrzej Siewior
2019-05-01 21:29     ` John Johansen
2019-05-02 10:51       ` Sebastian Andrzej Siewior
2019-05-02 13:17         ` Tetsuo Handa
2019-05-02 13:47           ` Sebastian Andrzej Siewior
2019-05-02 14:10             ` Tetsuo Handa
2019-05-03 11:48               ` [PATCH v2] " Sebastian Andrzej Siewior
2019-05-03 11:51                 ` [PATCH v3] " Sebastian Andrzej Siewior
2019-05-03 12:41                   ` Tetsuo Handa
2019-05-03 14:12                     ` [PATCH v4] " Sebastian Andrzej Siewior
2019-05-07 19:57                       ` John Johansen
2019-10-02  8:59                         ` Sebastian Andrzej Siewior
2019-10-02 15:47                           ` John Johansen
2019-10-02 15:52                             ` Sebastian Andrzej Siewior
2019-05-02 19:33         ` [PATCH 1/2] " John Johansen

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