linux-kernel - [PATCH v2] mm/mlock: fix potential imbalanced rlimit ucounts adjustment

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Message-ID: <20220314064039.62972-1-linmiaohe@huawei.com>
Date:   Mon, 14 Mar 2022 14:40:39 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>, <hughd@...gle.com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH v2] mm/mlock: fix potential imbalanced rlimit ucounts adjustment

user_shm_lock forgets to set allowed to 0 when get_ucounts fails. So
the later user_shm_unlock might do the extra dec_rlimit_ucounts. Fix
this by resetting allowed to 0.

Fixes: d7c9e99aee48 ("Reimplement RLIMIT_MEMLOCK on top of ucounts")
Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
Acked-by: Hugh Dickins <hughd@...gle.com>
---
v1->v2:
  correct Fixes tag and collect Acked-by tag
  Thanks Hugh for review!
---
 mm/mlock.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/mlock.c b/mm/mlock.c
index 29372c0eebe5..efd2dd2943de 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -733,6 +733,7 @@ int user_shm_lock(size_t size, struct ucounts *ucounts)
 	}
 	if (!get_ucounts(ucounts)) {
 		dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked);
+		allowed = 0;
 		goto out;
 	}
 	allowed = 1;
-- 
2.23.0