1 files changed, 14 insertions, 3 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index c6bef6e404fe..e9251d934f7d 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2458,9 +2458,20 @@ retry:
                  * userspace.
                  */
                 mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
-                if (futex_atomic_cmpxchg_inatomic(&nval, uaddr, uval, mval))
-                        return -1;
-
+                /*
+                 * We are not holding a lock here, but we want to have
+                 * the pagefault_disable/enable() protection because
+                 * we want to handle the fault gracefully. If the
+                 * access fails we try to fault in the futex with R/W
+                 * verification via get_user_pages. get_user() above
+                 * does not guarantee R/W access. If that fails we
+                 * give up and leave the futex locked.
+                 */
+                if (cmpxchg_futex_value_locked(&nval, uaddr, uval, mval)) {
+                        if (fault_in_user_writeable(uaddr))
+                                return -1;
+                        goto retry;
+                }
                 if (nval != uval)
                         goto retry;