linux-kernel - Re: [PATCH] tty: synclink_gt: Fix null-pointer-dereference in slgt

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Message-ID: <f9e0d516-d3a7-c0bf-f673-2a4c3dd9184d@kernel.org>
Date:   Mon, 11 Apr 2022 12:12:59 +0200
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Zheyu Ma <zheyuma97@...il.com>, gregkh@...uxfoundation.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tty: synclink_gt: Fix null-pointer-dereference in
 slgt_clean()

On 10. 04. 22, 13:48, Zheyu Ma wrote:
> When the driver fails at alloc_hdlcdev(), and then we remove the driver
> module, we will get the following splat:
> 
> [   25.065966] general protection fault, probably for non-canonical address 0xdffffc0000000182: 0000 [#1] PREEMPT SMP KASAN PTI
> [   25.066914] KASAN: null-ptr-deref in range [0x0000000000000c10-0x0000000000000c17]
> [   25.069262] RIP: 0010:detach_hdlc_protocol+0x2a/0x3e0
> [   25.077709] Call Trace:
> [   25.077924]  <TASK>
> [   25.078108]  unregister_hdlc_device+0x16/0x30
> [   25.078481]  slgt_cleanup+0x157/0x9f0 [synclink_gt]
> 
> Fix this by checking whether the 'info->netdev' is a null pointer first.

Hi,

LGTM

Reviewed-by: Jiri Slaby <jirislaby@...nel.org>

Out of curiosity, do you use the driver, or you only do some static 
analysis?

> Signed-off-by: Zheyu Ma <zheyuma97@...il.com>
> ---
>   drivers/tty/synclink_gt.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/tty/synclink_gt.c b/drivers/tty/synclink_gt.c
> index 25c558e65ece..9bc2a9265277 100644
> --- a/drivers/tty/synclink_gt.c
> +++ b/drivers/tty/synclink_gt.c
> @@ -1746,6 +1746,8 @@ static int hdlcdev_init(struct slgt_info *info)
>    */
>   static void hdlcdev_exit(struct slgt_info *info)
>   {
> +	if (!info->netdev)
> +		return;
>   	unregister_hdlc_device(info->netdev);
>   	free_netdev(info->netdev);
>   	info->netdev = NULL;


-- 
js
suse labs