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sched, modules: Fix nested sleep in add_unformed_module()

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This is a genuine bug in add_unformed_module(), we cannot use blocking
primitives inside a wait loop.

So rewrite the wait_event_interruptible() usage to use the fresh
wait_woken() stuff.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: tglx@linutronix.de
Cc: ilya.dryomov@inktank.com
Cc: umgwanakikbuti@gmail.com
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: oleg@redhat.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: http://lkml.kernel.org/r/20140924082242.458562904@infradead.org
[ So this is probably complex to backport and the race wasn't reported AFAIK,
  so not marked for -stable. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2014-09-24 10:18:53 +02:00 committed by Ingo Molnar
parent 7d4d26966e
commit 3c9b2c3d64
1 changed files with 28 additions and 2 deletions
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30
kernel/module.c
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@ -3096,6 +3096,32 @@ static int may_init_module(void)
return 0;
}
/*
* Can't use wait_event_interruptible() because our condition
* 'finished_loading()' contains a blocking primitive itself (mutex_lock).
*/
static int wait_finished_loading(struct module *mod)
{
DEFINE_WAIT_FUNC(wait, woken_wake_function);
int ret = 0;
add_wait_queue(&module_wq, &wait);
for (;;) {
if (finished_loading(mod->name))
break;
if (signal_pending(current)) {
ret = -ERESTARTSYS;
break;
}
wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
}
remove_wait_queue(&module_wq, &wait);
return ret;
}
/*
* We try to place it in the list now to make sure it's unique before
* we dedicate too many resources. In particular, temporary percpu
@ -3116,8 +3142,8 @@ static int add_unformed_module(struct module *mod)
|| old->state == MODULE_STATE_UNFORMED) {
/* Wait in case it fails to load. */
mutex_unlock(&module_mutex);
err = wait_event_interruptible(module_wq,
finished_loading(mod->name));
err = wait_finished_loading(mod);
if (err)
goto out_unlocked;
goto again;