The patch titled
Subject: userfaultfd/shmem: fix minor fault page leak
has been added to the -mm tree. Its filename is
userfaultfd-support-minor-fault-handling-for-shmem-fix-2.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/userfaultfd-support-minor-fault-handling-for-shmem-fix-2.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/userfaultfd-support-minor-fault-handling-for-shmem-fix-2.patch
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------------------------------------------------------
From: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Subject: userfaultfd/shmem: fix minor fault page leak
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.
Link: https://lkml.kernel.org/r/20210322204836.1650221-1-axelrasmussen@xxxxxxxxxx
Fixes: 00da60b9d0a0 ("userfaultfd: support minor fault handling for shmem")
Signed-off-by: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/shmem.c | 1 +
1 file changed, 1 insertion(+)
--- a/mm/shmem.c~userfaultfd-support-minor-fault-handling-for-shmem-fix-2
+++ a/mm/shmem.c
@@ -1831,6 +1831,7 @@ repeat:
if (page && vma && userfaultfd_minor(vma)) {
unlock_page(page);
+ put_page(page);
*fault_type = handle_userfault(vmf, VM_UFFD_MINOR);
return 0;
}
_
Patches currently in -mm which might be from axelrasmussen@xxxxxxxxxx are
userfaultfd-add-minor-fault-registration-mode.patch
userfaultfd-disable-huge-pmd-sharing-for-minor-registered-vmas.patch
userfaultfd-hugetlbfs-only-compile-uffd-helpers-if-config-enabled.patch
userfaultfd-add-uffdio_continue-ioctl.patch
userfaultfd-update-documentation-to-describe-minor-fault-handling.patch
userfaultfd-selftests-add-test-exercising-minor-fault-handling.patch
userfaultfd-support-minor-fault-handling-for-shmem.patch
userfaultfd-support-minor-fault-handling-for-shmem-fix.patch
userfaultfd-support-minor-fault-handling-for-shmem-fix-2.patch
userfaultfd-selftests-use-memfd_create-for-shmem-test-type.patch
userfaultfd-selftests-create-alias-mappings-in-the-shmem-test.patch
userfaultfd-selftests-reinitialize-test-context-in-each-test.patch
userfaultfd-selftests-exercise-minor-fault-handling-shmem-support.patch
