Re: [PATCH] PM / hibernate: Fix oops at snapshot_write().

From: Rafael J. Wysocki
Date: Tue May 29 2018 - 04:49:27 EST


On Saturday, May 26, 2018 2:59:36 AM CEST Tetsuo Handa wrote:
> 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>
> Cc: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>
> Cc: Len Brown <len.brown@xxxxxxxxx>
> Cc: Pavel Machek <pavel@xxxxxx>
> ---
> kernel/power/user.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/kernel/power/user.c b/kernel/power/user.c
> index 75c959d..abd2255 100644
> --- 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)
>

Applied, thanks!