[127/227] mm/mlock: fix potential imbalanced rlimit ucounts adjustment

Commit Message

Andrew Morton March 22, 2022, 9:44 p.m. UTC

From: Miaohe Lin <[e-mail]>
Subject: 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.

Link: https://lkml.kernel.org/r/[e-mail]
Fixes: d7c9e99aee48 ("Reimplement RLIMIT_MEMLOCK on top of ucounts")
Signed-off-by: Miaohe Lin <[e-mail]>
Reviewed-by: Andrew Morton <[e-mail]>
Acked-by: Hugh Dickins <[e-mail]>
Cc: Herbert van den Bergh <[e-mail]>
Cc: Chris Mason <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/mlock.c |    1 +
 1 file changed, 1 insertion(+)

Patch

--- a/mm/mlock.c~mm-mlock-fix-potential-imbalanced-rlimit-ucounts-adjustment
+++ a/mm/mlock.c
@@ -839,6 +839,7 @@  int user_shm_lock(size_t size, struct uc
 	}
 	if (!get_ucounts(ucounts)) {
 		dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked);
+		allowed = 0;
 		goto out;
 	}
 	allowed = 1;