From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Date: Tue, 9 Nov 2010 20:26:56 +0000 (+0100)
Subject: ioprio: rcu_read_lock/unlock protect find_task_by_vpid call (V2)
X-Git-Tag: v2.6.37-rc2~30^2~4
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f85acd81aa623e3dcf268c90e5cd8ecf36830984;p=pandora-kernel.git

ioprio: rcu_read_lock/unlock protect find_task_by_vpid call (V2)

Commit 4221a9918e38b7494cee341dda7b7b4bb8c04bde "Add RCU check for
find_task_by_vpid()" introduced rcu_lockdep_assert to find_task_by_pid_ns=

Assertion failed in sys_ioprio_get. The patch is fixing assertion
failure in ioprio_set as well.

 kernel/pid.c:419 invoked rcu_dereference_check() without protection!

 stack backtrace:
 Pid: 4254, comm: iotop Not tainted
 Call Trace:
 [<ffffffff810656f2>] lockdep_rcu_dereference+0xaa/0xb2
 [<ffffffff81053c67>] find_task_by_pid_ns+0x4f/0x68
 [<ffffffff81053c9d>] find_task_by_vpid+0x1d/0x1f
 [<ffffffff811104e2>] sys_ioprio_get+0x50/0x2da
 [<ffffffff81002182>] system_call_fastpath+0x16/0x1b

V2: rcu critical section expanded according to comment by Paul E. McKenney

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
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