[PATCH 4.17 59/67] PM / hibernate: Fix oops at snapshot_write()

From: Greg Kroah-Hartman
Date: Mon Jul 16 2018 - 03:38:57 EST


4.17-stable review patch. If anyone has any objections, please let me know.

------------------

From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>

commit fc14eebfc20854a38fd9f1d93a42b1783dad4d17 upstream.

syzbot is reporting NULL pointer dereference at snapshot_write() [1].
This is because data->handle is zero-cleared by ioctl(SNAPSHOT_FREE).
Fix this by checking data_of(data->handle) != NULL before using it.

[1] https://syzkaller.appspot.com/bug?id=828a3c71bd344a6de8b6a31233d51a72099f27fd

Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Reported-by: syzbot <syzbot+ae590932da6e45d6564d@xxxxxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
kernel/power/user.c | 5 +++++
1 file changed, 5 insertions(+)

--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -186,6 +186,11 @@ static ssize_t snapshot_write(struct fil
res = PAGE_SIZE - pg_offp;
}

+ if (!data_of(data->handle)) {
+ res = -EINVAL;
+ goto unlock;
+ }
+
res = simple_write_to_buffer(data_of(data->handle), res, &pg_offp,
buf, count);
if (res > 0)