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authorMiaohe Lin <linmiaohe@huawei.com>2022-04-08 13:09:07 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-04-08 14:20:36 -1000
commit4ad099559b00ac01c3726e5c95dc3108ef47d03e (patch)
tree9f7e3db92c4f57ffb916286f34b601b38a50da7f /mm
parent01e67e04c28170c47700c2c226d732bbfedb1ad0 (diff)
mm/mempolicy: fix mpol_new leak in shared_policy_replace
If mpol_new is allocated but not used in restart loop, mpol_new will be freed via mpol_put before returning to the caller. But refcnt is not initialized yet, so mpol_put could not do the right things and might leak the unused mpol_new. This would happen if mempolicy was updated on the shared shmem file while the sp->lock has been dropped during the memory allocation. This issue could be triggered easily with the below code snippet if there are many processes doing the below work at the same time: shmid = shmget((key_t)5566, 1024 * PAGE_SIZE, 0666|IPC_CREAT); shm = shmat(shmid, 0, 0); loop many times { mbind(shm, 1024 * PAGE_SIZE, MPOL_LOCAL, mask, maxnode, 0); mbind(shm + 128 * PAGE_SIZE, 128 * PAGE_SIZE, MPOL_DEFAULT, mask, maxnode, 0); } Link: https://lkml.kernel.org/r/20220329111416.27954-1-linmiaohe@huawei.com Fixes: 42288fe366c4 ("mm: mempolicy: Convert shared_policy mutex to spinlock") Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Mel Gorman <mgorman@suse.de> Cc: <stable@vger.kernel.org> [3.8] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/mempolicy.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 358b7c11426d..88a74bc4cba5 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2733,6 +2733,7 @@ alloc_new:
mpol_new = kmem_cache_alloc(policy_cache, GFP_KERNEL);
if (!mpol_new)
goto err_out;
+ atomic_set(&mpol_new->refcnt, 1);
goto restart;
}