[patch 2/9] fs: Add missing rcu protection for __task_cred() in sys_ioprio_get

Thomas Gleixner
2009-12-10T00:54:22Z

[-- Attachment #1: fs-fix-missing-rcu-protection-of-__task_cred.patch --]
[-- Type: text/plain, Size: 1112 bytes --]

sys_ioprio_get() accesses __task_cred() without being in a RCU read
side critical section. tasklist_lock is not protecting that when
CONFIG_TREE_PREEMPT_RCU=y.

Add a rcu_read_lock/unlock() section around the code which accesses
__task_cred().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: David Howells <dhowells@redhat.com>
Cc: James Morris <jmorris@namei.org>
Cc: linux-security-module@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Cc: Al Viro <viro@zeniv.linux.org.uk>
---
fs/ioprio.c | 2 ++
1 file changed, 2 insertions(+)

Index: linux-2.6-tip/fs/ioprio.c
===================================================================
--- linux-2.6-tip.orig/fs/ioprio.c
+++ linux-2.6-tip/fs/ioprio.c
@@ -230,6 +230,7 @@ SYSCALL_DEFINE2(ioprio_get, int, which,
if (!user)
break;

+ rcu_read_lock();
do_each_thread(g, p) {
if (__task_cred(p)->uid != user->uid)
continue;
@@ -241,6 +242,7 @@ SYSCALL_DEFINE2(ioprio_get, int, which,
else
ret = ioprio_best(ret, tmpio);
} while_each_thread(g, p);
+ rcu_read_unlock();

if (who)
free_uid(user);