[PATCH] ipc,sem: prevent releasing RCU read lock twice in semctl_main

[Sasha Levin]

We will release RCU read lock twice if the sem id passed from userspace is
not within the legal range in semctl_main.

Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
Reviewed-by: Davidlohr Bueso <davidlohr.bueso@xxxxxx>
Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
 ipc/sem.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/ipc/sem.c b/ipc/sem.c
index 6e109ef..ac36671 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -1333,8 +1333,10 @@ static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
 	/* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
 	}
 	err = -EINVAL;
-	if(semnum < 0 || semnum >= nsems)
-		goto out_unlock;
+	if(semnum < 0 || semnum >= nsems) {
+		rcu_read_unlock();
+		goto out_wakeup;
+	}
 
 	sem_lock(sma, NULL, -1);
 	curr = &sma->sem_base[semnum];
-- 
1.8.1.5

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