[Devel] [PATCH VZ9] ms/ipc/sem: do not sleep with a spin lock held

[Vasily Averin]

We can't call kvfree() with a spin lock held, so defer it.

Link: https://lkml.kernel.org/r/20211223031207.556189-1-chi.minghao@zte.com.cn
Fixes: fc37a3b8b438 ("[PATCH] ipc sem: use kvmalloc for sem_undo allocation")
Reported-by: Zeal Robot <zealci at zte.com.cn>
Signed-off-by: Minghao Chi <chi.minghao at zte.com.cn>
Reviewed-by: Shakeel Butt <shakeelb at google.com>
Reviewed-by: Manfred Spraul <manfred at colorfullife.com>
Cc: Arnd Bergmann <arnd at arndb.de>
Cc: Yang Guang <cgel.zte at gmail.com>
Cc: Davidlohr Bueso <dbueso at suse.de>
Cc: Randy Dunlap <rdunlap at infradead.org>
Cc: Bhaskar Chowdhury <unixbhaskar at gmail.com>
Cc: Vasily Averin <vvs at virtuozzo.com>
Cc: <stable at vger.kernel.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
(cherry picked from commit 520ba724061cef59763e2b6f5b26e8387c2e5822)
Signed-off-by: Vasily Averin <vvs at virtuozzo.com>
---
  ipc/sem.c | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ipc/sem.c b/ipc/sem.c
index 4c4fdf010793..863f3d32d20a 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -1964,6 +1964,7 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
  	 */
  	un = lookup_undo(ulp, semid);
  	if (un) {
+		spin_unlock(&ulp->lock);
  		kvfree(new);
  		goto success;
  	}
@@ -1976,9 +1977,8 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
  	ipc_assert_locked_object(&sma->sem_perm);
  	list_add(&new->list_id, &sma->list_id);
  	un = new;
-
+	spin_unlock(&ulp->lock);
  success:
-	spin_unlock(&ulp->lock);
  	sem_unlock(sma, -1);
  out:
  	return un;
-- 
2.25.1