Messages in this thread Patch in this message | | | Date | Fri, 29 Oct 2010 15:55:50 +0300 | From | Sergey Senozhatsky <> | Subject | [PATCH] rcu_read_lock/unlock protect find_task_by_vpid call |
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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.
=================================================== [ INFO: suspicious rcu_dereference_check() usage. ] --------------------------------------------------- kernel/pid.c:419 invoked rcu_dereference_check() without protection! rcu_scheduler_active = 1, debug_locks = 0 1 lock held by iotop/4254: #0: (tasklist_lock){.?.?..}, at: [<ffffffff811104b4>] sys_ioprio_get+0x22/0x2da 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
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..666343d 100644 --- a/fs/ioprio.c +++ b/fs/ioprio.c @@ -113,8 +113,11 @@ SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio) case IOPRIO_WHO_PROCESS: if (!who) p = current; - else + else { + rcu_read_lock(); p = find_task_by_vpid(who); + rcu_read_unlock(); + } if (p) ret = set_task_ioprio(p, ioprio); break; @@ -202,8 +205,11 @@ SYSCALL_DEFINE2(ioprio_get, int, which, int, who) case IOPRIO_WHO_PROCESS: if (!who) p = current; - else + else { + rcu_read_lock(); p = find_task_by_vpid(who); + rcu_read_unlock(); + } if (p) ret = get_task_ioprio(p); break;
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