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

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Date:   Mon, 11 Apr 2022 18:46:53 +0800
From:   Zheyu Ma <zheyuma97@...il.com>
To:     Jiri Slaby <jirislaby@...nel.org>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tty: synclink_gt: Fix null-pointer-dereference in slgt_clean()

On Mon, Apr 11, 2022 at 6:13 PM Jiri Slaby <jirislaby@...nel.org> wrote:
>
> 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?

In fact, neither. I test the driver via fuzzing in a simulated environment.

Zheyu Ma