oom: stop allocating user memory if TIF_MEMDIE is set
get_user_pages() can try to allocate a nearly unlimited amount of memory on
behalf of a user process, even if that process has been OOM killed. The
OOM kill occurs upon return to user space via a SIGKILL, but
get_user_pages() will try allocate all its memory before returning. Change
get_user_pages() to check for TIF_MEMDIE, and if set then return
immediately.
Signed-off-by: Ethan Solomita <solo@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memory.c b/mm/memory.c
index ee29259..cfddcd2 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1055,6 +1055,14 @@
do {
struct page *page;
+ /*
+ * If tsk is ooming, cut off its access to large memory
+ * allocations. It has a pending SIGKILL, but it can't
+ * be processed until returning to user space.
+ */
+ if (unlikely(test_tsk_thread_flag(tsk, TIF_MEMDIE)))
+ return -ENOMEM;
+
if (write)
foll_flags |= FOLL_WRITE;