Messages in this thread Patch in this message | | | Date | Wed, 24 Nov 2010 20:35:57 -0500 | From | Dave Jones <> | Subject | rcu_read_lock/unlock protect find_task_by_vpid call in check_clock |
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=================================================== [ INFO: suspicious rcu_dereference_check() usage. ] --------------------------------------------------- kernel/pid.c:419 invoked rcu_dereference_check() without protection!
other info that might help us debug this:
rcu_scheduler_active = 1, debug_locks = 1 1 lock held by scrashme/13382: #0: (tasklist_lock){.?.?..}, at: [<ffffffff8106ddea>] check_clock+0x46/0x9a
stack backtrace: Pid: 13382, comm: scrashme Not tainted 2.6.37-rc3+ #8 Call Trace: [<ffffffff8107cfe1>] lockdep_rcu_dereference+0x9d/0xa5 [<ffffffff81069d08>] find_task_by_pid_ns+0x44/0x5d [<ffffffff81069d43>] find_task_by_vpid+0x22/0x24 [<ffffffff8106ddf2>] check_clock+0x4e/0x9a [<ffffffff8106deac>] posix_cpu_clock_getres+0x16/0x41 [<ffffffff8106be74>] sys_clock_getres+0x39/0xa0 [<ffffffff81009cb2>] system_call_fastpath+0x16/0x1b
Signed-off-by: Dave Jones <davej@redhat.com>
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c index 6842eeb..4bef9aa 100644 --- a/kernel/posix-cpu-timers.c +++ b/kernel/posix-cpu-timers.c @@ -38,11 +38,13 @@ static int check_clock(const clockid_t which_clock) return 0; read_lock(&tasklist_lock); + rcu_read_lock(); p = find_task_by_vpid(pid); if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ? same_thread_group(p, current) : thread_group_leader(p))) { error = -EINVAL; } + rcu_read_unlock(); read_unlock(&tasklist_lock); return error;
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