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From: Alexey Gladkov <gladkov.alexey@gmail.com>
To: LKML <linux-kernel@vger.kernel.org>,
	Kernel Hardening <kernel-hardening@lists.openwall.com>,
	Linux API <linux-api@vger.kernel.org>,
	Linux FS Devel <linux-fsdevel@vger.kernel.org>,
	Linux Security Module <linux-security-module@vger.kernel.org>
Cc: Akinobu Mita <akinobu.mita@gmail.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	Alexey Gladkov <gladkov.alexey@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andy Lutomirski <luto@kernel.org>,
	Daniel Micay <danielmicay@gmail.com>,
	Djalal Harouni <tixxdz@gmail.com>,
	"Dmitry V . Levin" <ldv@altlinux.org>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Ingo Molnar <mingo@kernel.org>,
	"J . Bruce Fields" <bfields@fieldses.org>,
	Jeff Layton <jlayton@poochiereds.net>,
	Jonathan Corbet <corbet@lwn.net>,
	Kees Cook <keescook@chromium.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Oleg Nesterov <oleg@redhat.com>,
	Solar Designer <solar@openwall.com>
Subject: [PATCH v8 07/11] proc: flush task dcache entries from all procfs instances
Date: Mon, 10 Feb 2020 16:05:15 +0100
Message-ID: <20200210150519.538333-8-gladkov.alexey@gmail.com> (raw)
In-Reply-To: <20200210150519.538333-1-gladkov.alexey@gmail.com>

This allows to flush dcache entries of a task on multiple procfs mounts
per pid namespace.

The RCU lock is used because the number of reads at the task exit time
is much larger than the number of procfs mounts.

Cc: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Djalal Harouni <tixxdz@gmail.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com>
---
 fs/proc/base.c                | 20 +++++++++++++++-----
 fs/proc/root.c                | 27 ++++++++++++++++++++++++++-
 include/linux/pid_namespace.h |  2 ++
 include/linux/proc_fs.h       |  2 ++
 4 files changed, 45 insertions(+), 6 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 4ccb280a3e79..24b7c620ded3 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3133,7 +3133,7 @@ static const struct inode_operations proc_tgid_base_inode_operations = {
 	.permission	= proc_pid_permission,
 };
 
-static void proc_flush_task_mnt(struct vfsmount *mnt, pid_t pid, pid_t tgid)
+static void proc_flush_task_mnt_root(struct dentry *mnt_root, pid_t pid, pid_t tgid)
 {
 	struct dentry *dentry, *leader, *dir;
 	char buf[10 + 1];
@@ -3142,7 +3142,7 @@ static void proc_flush_task_mnt(struct vfsmount *mnt, pid_t pid, pid_t tgid)
 	name.name = buf;
 	name.len = snprintf(buf, sizeof(buf), "%u", pid);
 	/* no ->d_hash() rejects on procfs */
-	dentry = d_hash_and_lookup(mnt->mnt_root, &name);
+	dentry = d_hash_and_lookup(mnt_root, &name);
 	if (dentry) {
 		d_invalidate(dentry);
 		dput(dentry);
@@ -3153,7 +3153,7 @@ static void proc_flush_task_mnt(struct vfsmount *mnt, pid_t pid, pid_t tgid)
 
 	name.name = buf;
 	name.len = snprintf(buf, sizeof(buf), "%u", tgid);
-	leader = d_hash_and_lookup(mnt->mnt_root, &name);
+	leader = d_hash_and_lookup(mnt_root, &name);
 	if (!leader)
 		goto out;
 
@@ -3208,14 +3208,24 @@ void proc_flush_task(struct task_struct *task)
 	int i;
 	struct pid *pid, *tgid;
 	struct upid *upid;
+	struct dentry *mnt_root;
+	struct proc_fs_info *fs_info;
 
 	pid = task_pid(task);
 	tgid = task_tgid(task);
 
 	for (i = 0; i <= pid->level; i++) {
 		upid = &pid->numbers[i];
-		proc_flush_task_mnt(upid->ns->proc_mnt, upid->nr,
-					tgid->numbers[i].nr);
+
+		rcu_read_lock();
+		list_for_each_entry_rcu(fs_info, &upid->ns->proc_mounts, pidns_entry) {
+			mnt_root = fs_info->m_super->s_root;
+			proc_flush_task_mnt_root(mnt_root, upid->nr, tgid->numbers[i].nr);
+		}
+		rcu_read_unlock();
+
+		mnt_root = upid->ns->proc_mnt->mnt_root;
+		proc_flush_task_mnt_root(mnt_root, upid->nr, tgid->numbers[i].nr);
 	}
 }
 
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 5d5cba4c899b..e2bb015da1a8 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -149,7 +149,22 @@ static int proc_fill_super(struct super_block *s, struct fs_context *fc)
 	if (ret) {
 		return ret;
 	}
-	return proc_setup_thread_self(s);
+
+	ret = proc_setup_thread_self(s);
+	if (ret) {
+		return ret;
+	}
+
+	/*
+	 * back reference to flush dcache entries at process exit time.
+	 */
+	ctx->fs_info->m_super = s;
+
+	spin_lock(&pid_ns->proc_mounts_lock);
+	list_add_tail_rcu(&ctx->fs_info->pidns_entry, &pid_ns->proc_mounts);
+	spin_unlock(&pid_ns->proc_mounts_lock);
+
+	return 0;
 }
 
 static int proc_reconfigure(struct fs_context *fc)
@@ -211,10 +226,17 @@ static void proc_kill_sb(struct super_block *sb)
 {
 	struct proc_fs_info *fs_info = proc_sb_info(sb);
 
+	spin_lock(&fs_info->pid_ns->proc_mounts_lock);
+	list_del_rcu(&fs_info->pidns_entry);
+	spin_unlock(&fs_info->pid_ns->proc_mounts_lock);
+
+	synchronize_rcu();
+
 	if (fs_info->proc_self)
 		dput(fs_info->proc_self);
 	if (fs_info->proc_thread_self)
 		dput(fs_info->proc_thread_self);
+
 	kill_anon_super(sb);
 	put_pid_ns(fs_info->pid_ns);
 	kfree(fs_info);
@@ -336,6 +358,9 @@ int pid_ns_prepare_proc(struct pid_namespace *ns)
 		ctx->fs_info->pid_ns = ns;
 	}
 
+	spin_lock_init(&ns->proc_mounts_lock);
+	INIT_LIST_HEAD_RCU(&ns->proc_mounts);
+
 	mnt = fc_mount(fc);
 	put_fs_context(fc);
 	if (IS_ERR(mnt))
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 66f47f1afe0d..c36af1dfd862 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -26,6 +26,8 @@ struct pid_namespace {
 	struct pid_namespace *parent;
 #ifdef CONFIG_PROC_FS
 	struct vfsmount *proc_mnt; /* Internal proc mounted during each new pidns */
+	spinlock_t proc_mounts_lock;
+	struct list_head proc_mounts; /* list of separated procfs mounts */
 #endif
 #ifdef CONFIG_BSD_PROCESS_ACCT
 	struct fs_pin *bacct;
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index 5f0b1b7e4271..f307940f8311 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -20,6 +20,8 @@ enum {
 };
 
 struct proc_fs_info {
+	struct list_head pidns_entry;    /* Node in procfs_mounts of a pidns */
+	struct super_block *m_super;
 	struct pid_namespace *pid_ns;
 	struct dentry *proc_self;        /* For /proc/self */
 	struct dentry *proc_thread_self; /* For /proc/thread-self */
-- 
2.24.1


  parent reply index

Thread overview: 85+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-10 15:05 [PATCH v8 00/11] proc: modernize proc to support multiple private instances Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 01/11] proc: Rename struct proc_fs_info to proc_fs_opts Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 02/11] proc: add proc_fs_info struct to store proc information Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 03/11] proc: move /proc/{self|thread-self} dentries to proc_fs_info Alexey Gladkov
2020-02-10 18:23   ` Andy Lutomirski
2020-02-12 15:00     ` Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 04/11] proc: move hide_pid, pid_gid from pid_namespace " Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 05/11] proc: add helpers to set and get proc hidepid and gid mount options Alexey Gladkov
2020-02-10 18:30   ` Andy Lutomirski
2020-02-12 14:57     ` Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 06/11] proc: support mounting procfs instances inside same pid namespace Alexey Gladkov
2020-02-10 15:05 ` Alexey Gladkov [this message]
2020-02-10 17:46   ` [PATCH v8 07/11] proc: flush task dcache entries from all procfs instances Linus Torvalds
2020-02-10 19:23     ` Al Viro
2020-02-11  1:36   ` Eric W. Biederman
2020-02-11  4:01     ` Eric W. Biederman
2020-02-12 14:49     ` Alexey Gladkov
2020-02-12 14:59       ` Eric W. Biederman
2020-02-12 17:08         ` Alexey Gladkov
2020-02-12 18:45         ` Linus Torvalds
2020-02-12 19:16           ` Eric W. Biederman
2020-02-12 19:49             ` Linus Torvalds
2020-02-12 20:03               ` Al Viro
2020-02-12 20:35                 ` Linus Torvalds
2020-02-12 20:38                   ` Al Viro
2020-02-12 20:41                     ` Al Viro
2020-02-12 21:02                       ` Linus Torvalds
2020-02-12 21:46                         ` Eric W. Biederman
2020-02-13  0:48                           ` Linus Torvalds
2020-02-13  4:37                             ` Eric W. Biederman
2020-02-13  5:55                               ` Al Viro
2020-02-13 21:30                                 ` Linus Torvalds
2020-02-13 22:23                                   ` Al Viro
2020-02-13 22:47                                     ` Linus Torvalds
2020-02-14 14:15                                       ` Eric W. Biederman
2020-02-14  3:48                                 ` Eric W. Biederman
2020-02-20 20:46                               ` [PATCH 0/7] proc: Dentry flushing without proc_mnt Eric W. Biederman
2020-02-20 20:47                                 ` [PATCH 1/7] proc: Rename in proc_inode rename sysctl_inodes sibling_inodes Eric W. Biederman
2020-02-20 20:48                                 ` [PATCH 2/7] proc: Generalize proc_sys_prune_dcache into proc_prune_siblings_dcache Eric W. Biederman
2020-02-20 20:49                                 ` [PATCH 3/7] proc: Mov rcu_read_(lock|unlock) in proc_prune_siblings_dcache Eric W. Biederman
2020-02-20 22:33                                   ` Linus Torvalds
2020-02-20 20:49                                 ` [PATCH 4/7] proc: Use d_invalidate " Eric W. Biederman
2020-02-20 22:43                                   ` Linus Torvalds
2020-02-20 22:54                                   ` Al Viro
2020-02-20 23:00                                     ` Linus Torvalds
2020-02-20 23:03                                     ` Al Viro
2020-02-20 23:39                                       ` Eric W. Biederman
2020-02-20 20:51                                 ` [PATCH 5/7] proc: Clear the pieces of proc_inode that proc_evict_inode cares about Eric W. Biederman
2020-02-20 20:52                                 ` [PATCH 6/7] proc: Use a list of inodes to flush from proc Eric W. Biederman
2020-02-20 20:52                                 ` [PATCH 7/7] proc: Ensure we see the exit of each process tid exactly once Eric W. Biederman
2020-02-21 16:50                                   ` Oleg Nesterov
2020-02-22 15:46                                     ` Eric W. Biederman
2020-02-20 23:02                                 ` [PATCH 0/7] proc: Dentry flushing without proc_mnt Linus Torvalds
2020-02-20 23:07                                   ` Al Viro
2020-02-20 23:37                                     ` Eric W. Biederman
2020-02-24 16:25                                 ` [PATCH v2 0/6] " Eric W. Biederman
2020-02-24 16:26                                   ` [PATCH v2 1/6] proc: Rename in proc_inode rename sysctl_inodes sibling_inodes Eric W. Biederman
2020-02-24 16:27                                   ` [PATCH v2 2/6] proc: Generalize proc_sys_prune_dcache into proc_prune_siblings_dcache Eric W. Biederman
2020-02-24 16:27                                   ` [PATCH v2 3/6] proc: In proc_prune_siblings_dcache cache an aquired super block Eric W. Biederman
2020-02-24 16:28                                   ` [PATCH v2 4/6] proc: Use d_invalidate in proc_prune_siblings_dcache Eric W. Biederman
2020-02-24 16:28                                   ` [PATCH v2 5/6] proc: Clear the pieces of proc_inode that proc_evict_inode cares about Eric W. Biederman
2020-02-24 16:29                                   ` [PATCH v2 6/6] proc: Use a list of inodes to flush from proc Eric W. Biederman
2020-02-28 20:17                                   ` [PATCH 0/3] proc: Actually honor the mount options Eric W. Biederman
2020-02-28 20:18                                     ` [PATCH 1/3] uml: Don't consult current to find the proc_mnt in mconsole_proc Eric W. Biederman
2020-02-28 20:18                                     ` [PATCH 2/3] uml: Create a private mount of proc for mconsole Eric W. Biederman
2020-02-28 20:30                                       ` Christian Brauner
2020-02-28 21:28                                         ` Eric W. Biederman
2020-02-28 21:59                                           ` Christian Brauner
2020-02-28 20:19                                     ` [PATCH 3/3] proc: Remove the now unnecessary internal mount of proc Eric W. Biederman
2020-02-28 20:39                                       ` Christian Brauner
2020-02-28 21:40                                         ` Eric W. Biederman
2020-02-28 22:34                                     ` [PATCH 4/3] pid: Improve the comment about waiting in zap_pid_ns_processes Eric W. Biederman
2020-02-29  2:59                                       ` Christian Brauner
2020-02-14  3:49                     ` [PATCH v8 07/11] proc: flush task dcache entries from all procfs instances Eric W. Biederman
2020-02-12 19:47           ` Al Viro
2020-02-11 22:45   ` Al Viro
2020-02-12 14:26     ` Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 08/11] proc: instantiate only pids that we can ptrace on 'hidepid=4' mount option Alexey Gladkov
2020-02-10 16:29   ` Jordan Glover
2020-02-12 14:34     ` Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 09/11] proc: add option to mount only a pids subset Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 10/11] docs: proc: add documentation for "hidepid=4" and "subset=pidfs" options and new mount behavior Alexey Gladkov
2020-02-10 18:29   ` Andy Lutomirski
2020-02-12 16:03     ` Alexey Gladkov
2020-02-10 15:05 ` [PATCH v8 11/11] proc: Move hidepid values to uapi as they are user interface to mount Alexey Gladkov

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