From 02732576b13423dfb80f372d7b1bf4bd540dba30 Mon Sep 17 00:00:00 2001 From: Axel Rasmussen Date: Mon, 22 Mar 2021 13:48:35 -0700 Subject: [PATCH] FROMLIST: 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. Fixes: 00da60b9d0a0 ("userfaultfd: support minor fault handling for shmem") Signed-off-by: Axel Rasmussen Reviewed-by: Peter Xu Signed-off-by: Lokesh Gidra Link: https://lore.kernel.org/patchwork/patch/1400686/ Bug: 160737021 Bug: 169683130 Change-Id: I599f1434e24fce6e31d0d73c7f9c4714e9875b63 --- mm/shmem.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/shmem.c b/mm/shmem.c index 8f95179b5e16..d80be19d9688 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; }