Commit f85acd81 authored Nov 09, 2010 by Sergey Senozhatsky Committed by Jens Axboe Nov 10, 2010

ioprio: rcu_read_lock/unlock protect find_task_by_vpid call (V2)



Commit 4221a991 "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>

parent 1447399b

fs/ioprio.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -111,12 +111,14 @@ SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
		read_lock(&tasklist_lock);
		switch (which) {
		case IOPRIO_WHO_PROCESS:
		rcu_read_lock();
		if (!who)
		p = current;
		else
		p = find_task_by_vpid(who);
		if (p)
		ret = set_task_ioprio(p, ioprio);
		rcu_read_unlock();
		break;
		case IOPRIO_WHO_PGRP:
		if (!who)
		@@ -205,12 +207,14 @@ SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
		read_lock(&tasklist_lock);
		switch (which) {
		case IOPRIO_WHO_PROCESS:
		rcu_read_lock();
		if (!who)
		p = current;
		else
		p = find_task_by_vpid(who);
		if (p)
		ret = get_task_ioprio(p);
		rcu_read_unlock();
		break;
		case IOPRIO_WHO_PGRP:
		if (!who)