PM / hibernate: Fix oops at snapshot_write()

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

diff --git a/kernel/power/user.c b/kernel/power/user.c
index 22df9f7ff672425f1200c421eceff5a41c220ff2..69017a569f3023175547cb1e14eefa2234b1c8ed 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)