linux-kernel - Re: [PATCH] PM / hibernate: Fix oops at snapshot

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Date:   Tue, 29 May 2018 10:48:16 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzbot <syzbot+ae590932da6e45d6564d@...kaller.appspotmail.com>
Subject: Re: [PATCH] PM / hibernate: Fix oops at snapshot_write().

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@...ove.SAKURA.ne.jp>
> Reported-by: syzbot <syzbot+ae590932da6e45d6564d@...kaller.appspotmail.com>
> Cc: Rafael J. Wysocki <rjw@...ysocki.net>
> Cc: Len Brown <len.brown@...el.com>
> Cc: Pavel Machek <pavel@....cz>
> ---
>  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!