mm: fix error case in mlock downgrade reversion

Commit 27421e211a39784694b597dbf35848b88363c248, Manually revert
"mlock: downgrade mmap sem while populating mlocked regions", has
introduced its own regression: __mlock_vma_pages_range() may report
an error (for example, -EFAULT from trying to lock down pages from
beyond EOF), but mlock_vma_pages_range() must hide that from its
callers as before.

Reported-by: Sami Farin <safari-kernel@safari.iki.fi>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/mm/mlock.c b/mm/mlock.c
index 028ec482fdd..037161d61b4 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -311,7 +311,10 @@ long mlock_vma_pages_range(struct vm_area_struct *vma,
                         is_vm_hugetlb_page(vma) ||
                         vma == get_gate_vma(current))) {
 
-                return __mlock_vma_pages_range(vma, start, end, 1);
+                __mlock_vma_pages_range(vma, start, end, 1);
+
+                /* Hide errors from mmap() and other callers */
+                return 0;
         }
 
         /*