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* [PATCH v5 0/3] binder: use cred instead of task for security context
@ 2021-10-12 16:56 Todd Kjos
  2021-10-12 16:56 ` [PATCH v5 1/3] binder: use euid from cred instead of using task Todd Kjos
                   ` (4 more replies)
  0 siblings, 5 replies; 7+ messages in thread
From: Todd Kjos @ 2021-10-12 16:56 UTC (permalink / raw)
  To: gregkh, arve, tkjos, maco, christian, jmorris, serge, paul,
	stephen.smalley.work, eparis, keescook, jannh, jeffv, zohar,
	linux-security-module, selinux, devel, linux-kernel
  Cc: joel, kernel-team, Todd Kjos

This series fixes the possible use of an incorrect security context
when checking selinux permissions, getting a security ID, or lookup
up the euid.

The previous behavior was to save the group_leader 'struct task_struct'
in binder_open() and using that to obtain security IDs or euids.

This has been shown to be unreliable, so this series instead saves the
'struct cred' of the task that called binder_open(). This cred is used
for these lookups instead of the task.

v1 and v2 of this series were a single patch "binder: use euid from"
cred instead of using task". During review, Stephen Smalley identified
two more related issues so the corresponding patches were added to
the series.

v3:
- add 2 patches to fix getsecid and euid

v4:
- fix minor checkpatch issues
- fix build-break for !CONFIG_SECURITY

v5:
- reorder/refactor patches as suggested by Stephen Smalley so eiud fix
  is first and saves the cred during binder_open()
- set *secid=0 for !CONFIG_SECURITY version of secuirty_cred_getsecid()

Todd Kjos (3):
  binder: use euid from cred instead of using task
  binder: use cred instead of task for selinux checks
  binder: use cred instead of task for getsecid

 drivers/android/binder.c          | 14 ++++++++------
 drivers/android/binder_internal.h |  4 ++++
 include/linux/lsm_hook_defs.h     | 14 +++++++-------
 include/linux/lsm_hooks.h         | 14 +++++++-------
 include/linux/security.h          | 28 ++++++++++++++--------------
 security/security.c               | 14 +++++++-------
 security/selinux/hooks.c          | 48 +++++++++++++-----------------------------------
 7 files changed, 60 insertions(+), 76 deletions(-)

^ permalink raw reply	[flat|nested] 7+ messages in thread

* [PATCH v5 1/3] binder: use euid from cred instead of using task
  2021-10-12 16:56 [PATCH v5 0/3] binder: use cred instead of task for security context Todd Kjos
@ 2021-10-12 16:56 ` Todd Kjos
  2021-10-12 16:56 ` [PATCH v5 2/3] binder: use cred instead of task for selinux checks Todd Kjos
                   ` (3 subsequent siblings)
  4 siblings, 0 replies; 7+ messages in thread
From: Todd Kjos @ 2021-10-12 16:56 UTC (permalink / raw)
  To: gregkh, arve, tkjos, maco, christian, jmorris, serge, paul,
	stephen.smalley.work, eparis, keescook, jannh, jeffv, zohar,
	linux-security-module, selinux, devel, linux-kernel
  Cc: joel, kernel-team, Todd Kjos, stable

Save the 'struct cred' associated with a binder process
at initial open to avoid potential race conditions
when converting to an euid.

Set a transaction's sender_euid from the 'struct cred'
saved at binder_open() instead of looking up the euid
from the binder proc's 'struct task'. This ensures
the euid is associated with the security context that
of the task that opened binder.

Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
Signed-off-by: Todd Kjos <tkjos@google.com>
Suggested-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Suggested-by: Jann Horn <jannh@google.com>
Cc: stable@vger.kernel.org # 4.4+
---
v3: added this patch to series (as 3/3)
v5:
- combined with saving of 'struct cred' during binder_open()
- reordered to 1/1 as suggested by Stephen Smalley

 drivers/android/binder.c          | 4 +++-
 drivers/android/binder_internal.h | 4 ++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 9edacc8b9768..a396015e874a 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2711,7 +2711,7 @@ static void binder_transaction(struct binder_proc *proc,
 		t->from = thread;
 	else
 		t->from = NULL;
-	t->sender_euid = task_euid(proc->tsk);
+	t->sender_euid = proc->cred->euid;
 	t->to_proc = target_proc;
 	t->to_thread = target_thread;
 	t->code = tr->code;
@@ -4353,6 +4353,7 @@ static void binder_free_proc(struct binder_proc *proc)
 	}
 	binder_alloc_deferred_release(&proc->alloc);
 	put_task_struct(proc->tsk);
+	put_cred(proc->cred);
 	binder_stats_deleted(BINDER_STAT_PROC);
 	kfree(proc);
 }
@@ -5055,6 +5056,7 @@ static int binder_open(struct inode *nodp, struct file *filp)
 	spin_lock_init(&proc->outer_lock);
 	get_task_struct(current->group_leader);
 	proc->tsk = current->group_leader;
+	proc->cred = get_cred(filp->f_cred);
 	INIT_LIST_HEAD(&proc->todo);
 	init_waitqueue_head(&proc->freeze_wait);
 	proc->default_priority = task_nice(current);
diff --git a/drivers/android/binder_internal.h b/drivers/android/binder_internal.h
index 402c4d4362a8..d6b6b8cb7346 100644
--- a/drivers/android/binder_internal.h
+++ b/drivers/android/binder_internal.h
@@ -364,6 +364,9 @@ struct binder_ref {
  *                        (invariant after initialized)
  * @tsk                   task_struct for group_leader of process
  *                        (invariant after initialized)
+ * @cred                  struct cred associated with the `struct file`
+ *                        in binder_open()
+ *                        (invariant after initialized)
  * @deferred_work_node:   element for binder_deferred_list
  *                        (protected by binder_deferred_lock)
  * @deferred_work:        bitmap of deferred work to perform
@@ -426,6 +429,7 @@ struct binder_proc {
 	struct list_head waiting_threads;
 	int pid;
 	struct task_struct *tsk;
+	const struct cred *cred;
 	struct hlist_node deferred_work_node;
 	int deferred_work;
 	int outstanding_txns;
-- 
2.33.0.882.g93a45727a2-goog


^ permalink raw reply related	[flat|nested] 7+ messages in thread

* [PATCH v5 2/3] binder: use cred instead of task for selinux checks
  2021-10-12 16:56 [PATCH v5 0/3] binder: use cred instead of task for security context Todd Kjos
  2021-10-12 16:56 ` [PATCH v5 1/3] binder: use euid from cred instead of using task Todd Kjos
@ 2021-10-12 16:56 ` Todd Kjos
  2021-10-12 16:56 ` [PATCH v5 3/3] binder: use cred instead of task for getsecid Todd Kjos
                   ` (2 subsequent siblings)
  4 siblings, 0 replies; 7+ messages in thread
From: Todd Kjos @ 2021-10-12 16:56 UTC (permalink / raw)
  To: gregkh, arve, tkjos, maco, christian, jmorris, serge, paul,
	stephen.smalley.work, eparis, keescook, jannh, jeffv, zohar,
	linux-security-module, selinux, devel, linux-kernel
  Cc: joel, kernel-team, Todd Kjos, stable

Since binder was integrated with selinux, it has passed
'struct task_struct' associated with the binder_proc
to represent the source and target of transactions.
The conversion of task to SID was then done in the hook
implementations. It turns out that there are race conditions
which can result in an incorrect security context being used.

Fix by using the 'struct cred' saved during binder_open and pass
it to the selinux subsystem.

Fixes: 79af73079d75 ("Add security hooks to binder and implement the
hooks for SELinux.")
Suggested-by: Jann Horn <jannh@google.com>
Signed-off-by: Todd Kjos <tkjos@google.com>
Cc: stable@vger.kernel.org # 5.14 (need backport for earlier stables)
---
v2: updated comments as suggested by Paul Moore
v3: added 2 patches to fix related issues
v5: moved 'struct cred' save during binder_open() to patch 1/3

 drivers/android/binder.c      | 12 ++++-----
 include/linux/lsm_hook_defs.h | 14 +++++-----
 include/linux/lsm_hooks.h     | 14 +++++-----
 include/linux/security.h      | 28 ++++++++++----------
 security/security.c           | 14 +++++-----
 security/selinux/hooks.c      | 48 ++++++++++-------------------------
 6 files changed, 54 insertions(+), 76 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index a396015e874a..bc15325f0579 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2056,7 +2056,7 @@ static int binder_translate_binder(struct flat_binder_object *fp,
 		ret = -EINVAL;
 		goto done;
 	}
-	if (security_binder_transfer_binder(proc->tsk, target_proc->tsk)) {
+	if (security_binder_transfer_binder(proc->cred, target_proc->cred)) {
 		ret = -EPERM;
 		goto done;
 	}
@@ -2102,7 +2102,7 @@ static int binder_translate_handle(struct flat_binder_object *fp,
 				  proc->pid, thread->pid, fp->handle);
 		return -EINVAL;
 	}
-	if (security_binder_transfer_binder(proc->tsk, target_proc->tsk)) {
+	if (security_binder_transfer_binder(proc->cred, target_proc->cred)) {
 		ret = -EPERM;
 		goto done;
 	}
@@ -2190,7 +2190,7 @@ static int binder_translate_fd(u32 fd, binder_size_t fd_offset,
 		ret = -EBADF;
 		goto err_fget;
 	}
-	ret = security_binder_transfer_file(proc->tsk, target_proc->tsk, file);
+	ret = security_binder_transfer_file(proc->cred, target_proc->cred, file);
 	if (ret < 0) {
 		ret = -EPERM;
 		goto err_security;
@@ -2595,8 +2595,8 @@ static void binder_transaction(struct binder_proc *proc,
 			return_error_line = __LINE__;
 			goto err_invalid_target_handle;
 		}
-		if (security_binder_transaction(proc->tsk,
-						target_proc->tsk) < 0) {
+		if (security_binder_transaction(proc->cred,
+						target_proc->cred) < 0) {
 			return_error = BR_FAILED_REPLY;
 			return_error_param = -EPERM;
 			return_error_line = __LINE__;
@@ -4565,7 +4565,7 @@ static int binder_ioctl_set_ctx_mgr(struct file *filp,
 		ret = -EBUSY;
 		goto out;
 	}
-	ret = security_binder_set_context_mgr(proc->tsk);
+	ret = security_binder_set_context_mgr(proc->cred);
 	if (ret < 0)
 		goto out;
 	if (uid_valid(context->binder_context_mgr_uid)) {
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index 2adeea44c0d5..61590c1f2d33 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -26,13 +26,13 @@
  *   #undef LSM_HOOK
  * };
  */
-LSM_HOOK(int, 0, binder_set_context_mgr, struct task_struct *mgr)
-LSM_HOOK(int, 0, binder_transaction, struct task_struct *from,
-	 struct task_struct *to)
-LSM_HOOK(int, 0, binder_transfer_binder, struct task_struct *from,
-	 struct task_struct *to)
-LSM_HOOK(int, 0, binder_transfer_file, struct task_struct *from,
-	 struct task_struct *to, struct file *file)
+LSM_HOOK(int, 0, binder_set_context_mgr, const struct cred *mgr)
+LSM_HOOK(int, 0, binder_transaction, const struct cred *from,
+	 const struct cred *to)
+LSM_HOOK(int, 0, binder_transfer_binder, const struct cred *from,
+	 const struct cred *to)
+LSM_HOOK(int, 0, binder_transfer_file, const struct cred *from,
+	 const struct cred *to, struct file *file)
 LSM_HOOK(int, 0, ptrace_access_check, struct task_struct *child,
 	 unsigned int mode)
 LSM_HOOK(int, 0, ptrace_traceme, struct task_struct *parent)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 5c4c5c0602cb..59024618554e 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1313,22 +1313,22 @@
  *
  * @binder_set_context_mgr:
  *	Check whether @mgr is allowed to be the binder context manager.
- *	@mgr contains the task_struct for the task being registered.
+ *	@mgr contains the struct cred for the current binder process.
  *	Return 0 if permission is granted.
  * @binder_transaction:
  *	Check whether @from is allowed to invoke a binder transaction call
  *	to @to.
- *	@from contains the task_struct for the sending task.
- *	@to contains the task_struct for the receiving task.
+ *	@from contains the struct cred for the sending process.
+ *	@to contains the struct cred for the receiving process.
  * @binder_transfer_binder:
  *	Check whether @from is allowed to transfer a binder reference to @to.
- *	@from contains the task_struct for the sending task.
- *	@to contains the task_struct for the receiving task.
+ *	@from contains the struct cred for the sending process.
+ *	@to contains the struct cred for the receiving process.
  * @binder_transfer_file:
  *	Check whether @from is allowed to transfer @file to @to.
- *	@from contains the task_struct for the sending task.
+ *	@from contains the struct cred for the sending process.
  *	@file contains the struct file being transferred.
- *	@to contains the task_struct for the receiving task.
+ *	@to contains the struct cred for the receiving process.
  *
  * @ptrace_access_check:
  *	Check permission before allowing the current process to trace the
diff --git a/include/linux/security.h b/include/linux/security.h
index 5b7288521300..6344d3362df7 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -258,13 +258,13 @@ extern int security_init(void);
 extern int early_security_init(void);
 
 /* Security operations */
-int security_binder_set_context_mgr(struct task_struct *mgr);
-int security_binder_transaction(struct task_struct *from,
-				struct task_struct *to);
-int security_binder_transfer_binder(struct task_struct *from,
-				    struct task_struct *to);
-int security_binder_transfer_file(struct task_struct *from,
-				  struct task_struct *to, struct file *file);
+int security_binder_set_context_mgr(const struct cred *mgr);
+int security_binder_transaction(const struct cred *from,
+				const struct cred *to);
+int security_binder_transfer_binder(const struct cred *from,
+				    const struct cred *to);
+int security_binder_transfer_file(const struct cred *from,
+				  const struct cred *to, struct file *file);
 int security_ptrace_access_check(struct task_struct *child, unsigned int mode);
 int security_ptrace_traceme(struct task_struct *parent);
 int security_capget(struct task_struct *target,
@@ -508,25 +508,25 @@ static inline int early_security_init(void)
 	return 0;
 }
 
-static inline int security_binder_set_context_mgr(struct task_struct *mgr)
+static inline int security_binder_set_context_mgr(const struct cred *mgr)
 {
 	return 0;
 }
 
-static inline int security_binder_transaction(struct task_struct *from,
-					      struct task_struct *to)
+static inline int security_binder_transaction(const struct cred *from,
+					      const struct cred *to)
 {
 	return 0;
 }
 
-static inline int security_binder_transfer_binder(struct task_struct *from,
-						  struct task_struct *to)
+static inline int security_binder_transfer_binder(const struct cred *from,
+						  const struct cred *to)
 {
 	return 0;
 }
 
-static inline int security_binder_transfer_file(struct task_struct *from,
-						struct task_struct *to,
+static inline int security_binder_transfer_file(const struct cred *from,
+						const struct cred *to,
 						struct file *file)
 {
 	return 0;
diff --git a/security/security.c b/security/security.c
index 9ffa9e9c5c55..67264cb08fb3 100644
--- a/security/security.c
+++ b/security/security.c
@@ -747,25 +747,25 @@ static int lsm_superblock_alloc(struct super_block *sb)
 
 /* Security operations */
 
-int security_binder_set_context_mgr(struct task_struct *mgr)
+int security_binder_set_context_mgr(const struct cred *mgr)
 {
 	return call_int_hook(binder_set_context_mgr, 0, mgr);
 }
 
-int security_binder_transaction(struct task_struct *from,
-				struct task_struct *to)
+int security_binder_transaction(const struct cred *from,
+				const struct cred *to)
 {
 	return call_int_hook(binder_transaction, 0, from, to);
 }
 
-int security_binder_transfer_binder(struct task_struct *from,
-				    struct task_struct *to)
+int security_binder_transfer_binder(const struct cred *from,
+				    const struct cred *to)
 {
 	return call_int_hook(binder_transfer_binder, 0, from, to);
 }
 
-int security_binder_transfer_file(struct task_struct *from,
-				  struct task_struct *to, struct file *file)
+int security_binder_transfer_file(const struct cred *from,
+				  const struct cred *to, struct file *file)
 {
 	return call_int_hook(binder_transfer_file, 0, from, to, file);
 }
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index e7ebd45ca345..c8bf3db90c8b 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -255,29 +255,6 @@ static inline u32 task_sid_obj(const struct task_struct *task)
 	return sid;
 }
 
-/*
- * get the security ID of a task for use with binder
- */
-static inline u32 task_sid_binder(const struct task_struct *task)
-{
-	/*
-	 * In many case where this function is used we should be using the
-	 * task's subjective SID, but we can't reliably access the subjective
-	 * creds of a task other than our own so we must use the objective
-	 * creds/SID, which are safe to access.  The downside is that if a task
-	 * is temporarily overriding it's creds it will not be reflected here;
-	 * however, it isn't clear that binder would handle that case well
-	 * anyway.
-	 *
-	 * If this ever changes and we can safely reference the subjective
-	 * creds/SID of another task, this function will make it easier to
-	 * identify the various places where we make use of the task SIDs in
-	 * the binder code.  It is also likely that we will need to adjust
-	 * the main drivers/android binder code as well.
-	 */
-	return task_sid_obj(task);
-}
-
 static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dentry);
 
 /*
@@ -2066,18 +2043,19 @@ static inline u32 open_file_to_av(struct file *file)
 
 /* Hook functions begin here. */
 
-static int selinux_binder_set_context_mgr(struct task_struct *mgr)
+static int selinux_binder_set_context_mgr(const struct cred *mgr)
 {
 	return avc_has_perm(&selinux_state,
-			    current_sid(), task_sid_binder(mgr), SECCLASS_BINDER,
+			    current_sid(), cred_sid(mgr), SECCLASS_BINDER,
 			    BINDER__SET_CONTEXT_MGR, NULL);
 }
 
-static int selinux_binder_transaction(struct task_struct *from,
-				      struct task_struct *to)
+static int selinux_binder_transaction(const struct cred *from,
+				      const struct cred *to)
 {
 	u32 mysid = current_sid();
-	u32 fromsid = task_sid_binder(from);
+	u32 fromsid = cred_sid(from);
+	u32 tosid = cred_sid(to);
 	int rc;
 
 	if (mysid != fromsid) {
@@ -2088,24 +2066,24 @@ static int selinux_binder_transaction(struct task_struct *from,
 			return rc;
 	}
 
-	return avc_has_perm(&selinux_state, fromsid, task_sid_binder(to),
+	return avc_has_perm(&selinux_state, fromsid, tosid,
 			    SECCLASS_BINDER, BINDER__CALL, NULL);
 }
 
-static int selinux_binder_transfer_binder(struct task_struct *from,
-					  struct task_struct *to)
+static int selinux_binder_transfer_binder(const struct cred *from,
+					  const struct cred *to)
 {
 	return avc_has_perm(&selinux_state,
-			    task_sid_binder(from), task_sid_binder(to),
+			    cred_sid(from), cred_sid(to),
 			    SECCLASS_BINDER, BINDER__TRANSFER,
 			    NULL);
 }
 
-static int selinux_binder_transfer_file(struct task_struct *from,
-					struct task_struct *to,
+static int selinux_binder_transfer_file(const struct cred *from,
+					const struct cred *to,
 					struct file *file)
 {
-	u32 sid = task_sid_binder(to);
+	u32 sid = cred_sid(to);
 	struct file_security_struct *fsec = selinux_file(file);
 	struct dentry *dentry = file->f_path.dentry;
 	struct inode_security_struct *isec;
-- 
2.33.0.882.g93a45727a2-goog


^ permalink raw reply related	[flat|nested] 7+ messages in thread

* [PATCH v5 3/3] binder: use cred instead of task for getsecid
  2021-10-12 16:56 [PATCH v5 0/3] binder: use cred instead of task for security context Todd Kjos
  2021-10-12 16:56 ` [PATCH v5 1/3] binder: use euid from cred instead of using task Todd Kjos
  2021-10-12 16:56 ` [PATCH v5 2/3] binder: use cred instead of task for selinux checks Todd Kjos
@ 2021-10-12 16:56 ` Todd Kjos
  2021-10-12 17:49 ` [PATCH v5 0/3] binder: use cred instead of task for security context Casey Schaufler
  2021-10-14 21:33 ` Paul Moore
  4 siblings, 0 replies; 7+ messages in thread
From: Todd Kjos @ 2021-10-12 16:56 UTC (permalink / raw)
  To: gregkh, arve, tkjos, maco, christian, jmorris, serge, paul,
	stephen.smalley.work, eparis, keescook, jannh, jeffv, zohar,
	linux-security-module, selinux, devel, linux-kernel
  Cc: joel, kernel-team, Todd Kjos, kernel test robot, stable

Use the 'struct cred' saved at binder_open() to lookup
the security ID via security_cred_getsecid(). This
ensures that the security context that opened binder
is the one used to generate the secctx.

Fixes: ec74136ded79 ("binder: create node flag to request sender's
security context")
Signed-off-by: Todd Kjos <tkjos@google.com>
Suggested-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Cc: stable@vger.kernel.org # 5.4+
---
v3: added this patch to series
v4: fix build-break for !CONFIG_SECURITY
v5: set *secid=0 for !CONFIG_SECURITY version of secuirty_cred_getsecid()

 drivers/android/binder.c | 11 +----------
 include/linux/security.h |  5 +++++
 2 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index bc15325f0579..26382e982c5e 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2722,16 +2722,7 @@ static void binder_transaction(struct binder_proc *proc,
 		u32 secid;
 		size_t added_size;
 
-		/*
-		 * Arguably this should be the task's subjective LSM secid but
-		 * we can't reliably access the subjective creds of a task
-		 * other than our own so we must use the objective creds, which
-		 * are safe to access.  The downside is that if a task is
-		 * temporarily overriding it's creds it will not be reflected
-		 * here; however, it isn't clear that binder would handle that
-		 * case well anyway.
-		 */
-		security_task_getsecid_obj(proc->tsk, &secid);
+		security_cred_getsecid(proc->cred, &secid);
 		ret = security_secid_to_secctx(secid, &secctx, &secctx_sz);
 		if (ret) {
 			return_error = BR_FAILED_REPLY;
diff --git a/include/linux/security.h b/include/linux/security.h
index 6344d3362df7..46a02ce34d00 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1041,6 +1041,11 @@ static inline void security_transfer_creds(struct cred *new,
 {
 }
 
+static inline void security_cred_getsecid(const struct cred *c, u32 *secid)
+{
+	*secid = 0;
+}
+
 static inline int security_kernel_act_as(struct cred *cred, u32 secid)
 {
 	return 0;
-- 
2.33.0.882.g93a45727a2-goog


^ permalink raw reply related	[flat|nested] 7+ messages in thread

* Re: [PATCH v5 0/3] binder: use cred instead of task for security context
  2021-10-12 16:56 [PATCH v5 0/3] binder: use cred instead of task for security context Todd Kjos
                   ` (2 preceding siblings ...)
  2021-10-12 16:56 ` [PATCH v5 3/3] binder: use cred instead of task for getsecid Todd Kjos
@ 2021-10-12 17:49 ` Casey Schaufler
  2021-10-14 21:33 ` Paul Moore
  4 siblings, 0 replies; 7+ messages in thread
From: Casey Schaufler @ 2021-10-12 17:49 UTC (permalink / raw)
  To: Todd Kjos, gregkh, arve, tkjos, maco, christian, jmorris, serge,
	paul, stephen.smalley.work, eparis, keescook, jannh, jeffv,
	zohar, linux-security-module, selinux, devel, linux-kernel
  Cc: joel, kernel-team, Casey Schaufler

On 10/12/2021 9:56 AM, Todd Kjos wrote:
> This series fixes the possible use of an incorrect security context
> when checking selinux permissions, getting a security ID, or lookup
> up the euid.
>
> The previous behavior was to save the group_leader 'struct task_struct'
> in binder_open() and using that to obtain security IDs or euids.
>
> This has been shown to be unreliable, so this series instead saves the
> 'struct cred' of the task that called binder_open(). This cred is used
> for these lookups instead of the task.
>
> v1 and v2 of this series were a single patch "binder: use euid from"
> cred instead of using task". During review, Stephen Smalley identified
> two more related issues so the corresponding patches were added to
> the series.
>
> v3:
> - add 2 patches to fix getsecid and euid
>
> v4:
> - fix minor checkpatch issues
> - fix build-break for !CONFIG_SECURITY
>
> v5:
> - reorder/refactor patches as suggested by Stephen Smalley so eiud fix
>   is first and saves the cred during binder_open()
> - set *secid=0 for !CONFIG_SECURITY version of secuirty_cred_getsecid()
>
> Todd Kjos (3):
>   binder: use euid from cred instead of using task
>   binder: use cred instead of task for selinux checks
>   binder: use cred instead of task for getsecid
>
>  drivers/android/binder.c          | 14 ++++++++------
>  drivers/android/binder_internal.h |  4 ++++
>  include/linux/lsm_hook_defs.h     | 14 +++++++-------
>  include/linux/lsm_hooks.h         | 14 +++++++-------
>  include/linux/security.h          | 28 ++++++++++++++--------------
>  security/security.c               | 14 +++++++-------
>  security/selinux/hooks.c          | 48 +++++++++++++-----------------------------------
>  7 files changed, 60 insertions(+), 76 deletions(-)

For the series:
	Acked-by: Casey Schaufler <casey@schaufler-ca.com>


^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH v5 0/3] binder: use cred instead of task for security context
  2021-10-12 16:56 [PATCH v5 0/3] binder: use cred instead of task for security context Todd Kjos
                   ` (3 preceding siblings ...)
  2021-10-12 17:49 ` [PATCH v5 0/3] binder: use cred instead of task for security context Casey Schaufler
@ 2021-10-14 21:33 ` Paul Moore
  2021-10-14 21:40   ` Todd Kjos
  4 siblings, 1 reply; 7+ messages in thread
From: Paul Moore @ 2021-10-14 21:33 UTC (permalink / raw)
  To: Todd Kjos
  Cc: gregkh, arve, tkjos, maco, christian, James Morris, Serge Hallyn,
	Stephen Smalley, Eric Paris, keescook, jannh,
	Jeffrey Vander Stoep, zohar, linux-security-module, selinux,
	devel, linux-kernel, joel, kernel-team

On Tue, Oct 12, 2021 at 12:56 PM Todd Kjos <tkjos@google.com> wrote:
>
> This series fixes the possible use of an incorrect security context
> when checking selinux permissions, getting a security ID, or lookup
> up the euid.
>
> The previous behavior was to save the group_leader 'struct task_struct'
> in binder_open() and using that to obtain security IDs or euids.
>
> This has been shown to be unreliable, so this series instead saves the
> 'struct cred' of the task that called binder_open(). This cred is used
> for these lookups instead of the task.

Hi Todd,

I just merged all three patches into selinux/next, thanks for your
help patience on this patchset.  Ultimately I merged these patches
into selinux/next as opposed to selinux/stable-5.15 because I felt
that a couple of weeks in -next before going to Linus would be a good
thing.  I'm also not certain how widespread binder is outside of
Android so I figured the practical difference between next and
stable-5.15 is likely very small.  Regardless, all of your Fixes and
stable tags remain in the patches so as soon as they go up to Linus
during the next merge window the stable folks will be notified.

-- 
paul moore
www.paul-moore.com

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH v5 0/3] binder: use cred instead of task for security context
  2021-10-14 21:33 ` Paul Moore
@ 2021-10-14 21:40   ` Todd Kjos
  0 siblings, 0 replies; 7+ messages in thread
From: Todd Kjos @ 2021-10-14 21:40 UTC (permalink / raw)
  To: Paul Moore
  Cc: gregkh, arve, tkjos, maco, christian, James Morris, Serge Hallyn,
	Stephen Smalley, Eric Paris, keescook, jannh,
	Jeffrey Vander Stoep, zohar, linux-security-module, selinux,
	devel, linux-kernel, joel, kernel-team

On Thu, Oct 14, 2021 at 2:34 PM Paul Moore <paul@paul-moore.com> wrote:
>
> On Tue, Oct 12, 2021 at 12:56 PM Todd Kjos <tkjos@google.com> wrote:
> >
> > This series fixes the possible use of an incorrect security context
> > when checking selinux permissions, getting a security ID, or lookup
> > up the euid.
> >
> > The previous behavior was to save the group_leader 'struct task_struct'
> > in binder_open() and using that to obtain security IDs or euids.
> >
> > This has been shown to be unreliable, so this series instead saves the
> > 'struct cred' of the task that called binder_open(). This cred is used
> > for these lookups instead of the task.
>
> Hi Todd,
>
> I just merged all three patches into selinux/next, thanks for your
> help patience on this patchset.  Ultimately I merged these patches
> into selinux/next as opposed to selinux/stable-5.15 because I felt
> that a couple of weeks in -next before going to Linus would be a good
> thing.  I'm also not certain how widespread binder is outside of
> Android so I figured the practical difference between next and
> stable-5.15 is likely very small.  Regardless, all of your Fixes and
> stable tags remain in the patches so as soon as they go up to Linus
> during the next merge window the stable folks will be notified.

Thanks Paul. This all sounds fine.

>
> --
> paul moore
> www.paul-moore.com

^ permalink raw reply	[flat|nested] 7+ messages in thread

end of thread, other threads:[~2021-10-14 21:40 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-10-12 16:56 [PATCH v5 0/3] binder: use cred instead of task for security context Todd Kjos
2021-10-12 16:56 ` [PATCH v5 1/3] binder: use euid from cred instead of using task Todd Kjos
2021-10-12 16:56 ` [PATCH v5 2/3] binder: use cred instead of task for selinux checks Todd Kjos
2021-10-12 16:56 ` [PATCH v5 3/3] binder: use cred instead of task for getsecid Todd Kjos
2021-10-12 17:49 ` [PATCH v5 0/3] binder: use cred instead of task for security context Casey Schaufler
2021-10-14 21:33 ` Paul Moore
2021-10-14 21:40   ` Todd Kjos

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