+ proc-fix-a-race-in-do_io_accounting.patch added to -mm tree

+ proc-fix-a-race-in-do_io_accounting.patch added to -mm tree

[akpm]

The patch titled
     proc: fix a race in do_io_accounting()
has been added to the -mm tree.  Its filename is
     proc-fix-a-race-in-do_io_accounting.patch

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See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
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The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/

------------------------------------------------------
Subject: proc: fix a race in do_io_accounting()
From: Vasiliy Kulikov <segoon@openwall.com>

There is a ptrace_may_access() check in do_io_accounting() to prevent
gathering information of setuid'ed and similar binaries.  However, there
is a race against execve().  Holding task->signal->cred_guard_mutex while
gathering the information should protect against the race.

The order of locking is similar to the one inside of ptrace_attach():
first goes cred_guard_mutex, then lock_task_sighand().

Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/proc/base.c |   16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff -puN fs/proc/base.c~proc-fix-a-race-in-do_io_accounting fs/proc/base.c
--- a/fs/proc/base.c~proc-fix-a-race-in-do_io_accounting
+++ a/fs/proc/base.c
@@ -2718,9 +2718,16 @@ static int do_io_accounting(struct task_
 {
 	struct task_io_accounting acct = task->ioac;
 	unsigned long flags;
+	int result;
 
-	if (!ptrace_may_access(task, PTRACE_MODE_READ))
-		return -EACCES;
+	result = mutex_lock_killable(&task->signal->cred_guard_mutex);
+	if (result)
+		return result;
+
+	if (!ptrace_may_access(task, PTRACE_MODE_READ)) {
+		result = -EACCES;
+		goto out_unlock;
+	}
 
 	if (whole && lock_task_sighand(task, &flags)) {
 		struct task_struct *t = task;
@@ -2731,7 +2738,7 @@ static int do_io_accounting(struct task_
 
 		unlock_task_sighand(task, &flags);
 	}
-	return sprintf(buffer,
+	result = sprintf(buffer,
 			"rchar: %llu\n"
 			"wchar: %llu\n"
 			"syscr: %llu\n"
@@ -2746,6 +2753,9 @@ static int do_io_accounting(struct task_
 			(unsigned long long)acct.read_bytes,
 			(unsigned long long)acct.write_bytes,
 			(unsigned long long)acct.cancelled_write_bytes);
+out_unlock:
+	mutex_unlock(&task->signal->cred_guard_mutex);
+	return result;
 }
 
 static int proc_tid_io_accounting(struct task_struct *task, char *buffer)
_

Patches currently in -mm which might be from segoon@openwall.com are

arch-arm-mach-ux500-mbox-db5500c-world-writable-sysfs-fifo-file.patch
proc-fix-a-race-in-do_io_accounting.patch
ipc-introduce-shm_rmid_forced-sysctl.patch
ipc-introduce-shm_rmid_forced-sysctl-fix.patch
ipc-introduce-shm_rmid_forced-sysctl-fix-2.patch
ipc-introduce-shm_rmid_forced-sysctl-cleanup.patch
ipc-introduce-shm_rmid_forced-sysctl-comments.patch
ipc-introduce-shm_rmid_forced-sysctl-comments-fix.patch
ipc-introduce-shm_rmid_forced-sysctl-testing.patch