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md: protect md_unregister_thread from reentrancy

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[ Upstream commit 1e267742283a4b5a8ca65755c44166be27e9aa0f ]

Generally, the md_unregister_thread is called with reconfig_mutex, but
raid_message in dm-raid doesn't hold reconfig_mutex to unregister thread,
so md_unregister_thread can be called simulitaneously from two call sites
in theory.

Then after previous commit which remove the protection of reconfig_mutex
for md_unregister_thread completely, the potential issue could be worse
than before.

Let's take pers_lock at the beginning of function to ensure reentrancy.

Reported-by: Donald Buczek <buczek@molgen.mpg.de>
Signed-off-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Guoqing Jiang
2022-04-29 16:49:09 +08:00
committed by Greg Kroah-Hartman
parent 668c3f9fa2
commit 7eb32f286e
1 changed files with 10 additions and 5 deletions
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15
drivers/md/md.c
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@@ -7970,17 +7970,22 @@ EXPORT_SYMBOL(md_register_thread);
void md_unregister_thread(struct md_thread **threadp) void md_unregister_thread(struct md_thread **threadp)
{ {
struct md_thread *thread = *threadp; struct md_thread *thread;
if (!thread)
return; /*
pr_debug("interrupting MD-thread pid %d\n", task_pid_nr(thread->tsk)); * Locking ensures that mddev_unlock does not wake_up a
/* Locking ensures that mddev_unlock does not wake_up a
* non-existent thread * non-existent thread
*/ */
spin_lock(&pers_lock); spin_lock(&pers_lock);
thread = *threadp;
if (!thread) {
spin_unlock(&pers_lock);
return;
}
*threadp = NULL; *threadp = NULL;
spin_unlock(&pers_lock); spin_unlock(&pers_lock);
pr_debug("interrupting MD-thread pid %d\n", task_pid_nr(thread->tsk));
kthread_stop(thread->tsk); kthread_stop(thread->tsk);
kfree(thread); kfree(thread);
} }