Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | Date | Tue, 9 Nov 2010 12:21:24 +0200 | From | Sergey Senozhatsky <> | Subject | [PATCH] ioprio: rcu_read_lock/unlock protect find_task_by_vpid call (V2) |
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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. McKenne: | Looking over the patch again, the scope of the RCU read-side critical | section needs to expand to cover the use of the pointer as well as the | call to find_task_by_vpid().
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
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diff --git a/fs/ioprio.c b/fs/ioprio.c index 748cfb9..64cd50b 100644 --- a/fs/ioprio.c +++ b/fs/ioprio.c @@ -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) @@ -200,12 +202,14 @@ 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)
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