diff mbox series

[v4,3/8] mm: validate mm in do_madvise

Message ID 20200212233946.246210-4-minchan@kernel.org (mailing list archive)
State New, archived
Headers show
Series introduce memory hinting API for external process | expand

Commit Message

Minchan Kim Feb. 12, 2020, 11:39 p.m. UTC 
Oleg pointed out mm could be nulllified right after mm_access succeeds.
This patch validates it before the using.

Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
 mm/madvise.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/mm/madvise.c b/mm/madvise.c
index 8611f1d39289..bb04c7897eb9 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1073,7 +1073,11 @@  int do_madvise(struct task_struct *task, unsigned long start,
 	int write;
 	size_t len;
 	struct blk_plug plug;
-	struct mm_struct *mm = task->mm;
+	struct mm_struct *mm = READ_ONCE(task->mm);
+
+	/* task can exit and nullify its ->mm right after mm_access() */
+	if (!mm)
+		return -ESRCH;
 
 	start = untagged_addr(start);