From: Axel Rasmussen <axelrasmussen@google.com>
To: Alexander Viro <viro@zeniv.linux.org.uk>,
Andrea Arcangeli <aarcange@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
Jerome Glisse <jglisse@redhat.com>,
Joe Perches <joe@perches.com>,
Lokesh Gidra <lokeshgidra@google.com>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Peter Xu <peterx@redhat.com>, Shaohua Li <shli@fb.com>,
Shuah Khan <shuah@kernel.org>, Wang Qing <wangqing@vivo.com>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-kselftest@vger.kernel.org,
Axel Rasmussen <axelrasmussen@google.com>,
Brian Geffon <bgeffon@google.com>,
Cannon Matthews <cannonmatthews@google.com>,
"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
David Rientjes <rientjes@google.com>,
Michel Lespinasse <walken@google.com>,
Mina Almasry <almasrymina@google.com>,
Oliver Upton <oupton@google.com>
Subject: [PATCH] userfaultfd/shmem: fix minor fault page leak
Date: Mon, 22 Mar 2021 13:48:35 -0700 [thread overview]
Message-ID: <20210322204836.1650221-1-axelrasmussen@google.com> (raw)
This fix is analogous to Peter Xu's fix for hugetlb [0]. If we don't
put_page() after getting the page out of the page cache, we leak the
reference.
The fix can be verified by checking /proc/meminfo and running the
userfaultfd selftest in shmem mode. Without the fix, we see MemFree /
MemAvailable steadily decreasing with each run of the test. With the
fix, memory is correctly freed after the test program exits.
Fixes: 00da60b9d0a0 ("userfaultfd: support minor fault handling for shmem")
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
---
mm/shmem.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/mm/shmem.c b/mm/shmem.c
index ef8c9f5e92fc..d2e0e81b7d2e 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1831,6 +1831,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
if (page && vma && userfaultfd_minor(vma)) {
unlock_page(page);
+ put_page(page);
*fault_type = handle_userfault(vmf, VM_UFFD_MINOR);
return 0;
}
--
2.31.0.rc2.261.g7f71774620-goog
next reply other threads:[~2021-03-22 20:49 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-22 20:48 Axel Rasmussen [this message]
2021-03-22 21:00 ` [PATCH] userfaultfd/shmem: fix minor fault page leak Peter Xu
2021-03-24 23:20 ` Andrew Morton
2021-03-25 0:52 ` Peter Xu
2021-03-25 2:10 ` Axel Rasmussen
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