PM / hibernate: Fix oops at snapshot_write()

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@I-love.SAKURA.ne.jp>
Reported-by: syzbot <syzbot+ae590932da6e45d6564d@syzkaller.appspotmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/kernel/power/user.c b/kernel/power/user.c
index 75c959de4b29cb7e32d3cbbc21d4cbc5f5bb3db7..abd225550271352ddb4306c9d9b506c013be80ae 100644 (file)
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -186,6 +186,11 @@ static ssize_t snapshot_write(struct file *filp, const char __user *buf,
                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)