linux-kernel - Re: [PATCH] video: fbdev: sm712fb: Fix crash in smtcfb

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Date:   Thu, 3 Mar 2022 09:34:40 +0800
From:   Zheyu Ma <zheyuma97@...il.com>
To:     Helge Deller <deller@....de>
Cc:     sudipm.mukherjee@...il.com, teddy.wang@...iconmotion.com,
        linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] video: fbdev: sm712fb: Fix crash in smtcfb_write()

Hi,

On Thu, Mar 3, 2022 at 12:49 AM Helge Deller <deller@....de> wrote:
>
> On 3/2/22 15:33, Zheyu Ma wrote:
> > When the sm712fb driver writes three bytes to the framebuffer, the
> > driver will crash:
> >
> >     BUG: unable to handle page fault for address: ffffc90001ffffff
> >     RIP: 0010:smtcfb_write+0x454/0x5b0
> >     Call Trace:
> >      vfs_write+0x291/0xd60
> >      ? do_sys_openat2+0x27d/0x350
> >      ? __fget_light+0x54/0x340
> >      ksys_write+0xce/0x190
> >      do_syscall_64+0x43/0x90
> >      entry_SYSCALL_64_after_hwframe+0x44/0xae
> >
> > Fix it by removing the open-coded endianness fixup-code.
> >
> > Signed-off-by: Zheyu Ma <zheyuma97@...il.com>
>
> Thanks... it's already in the fbdev git tree and queued up for v5.18...
> https://git.kernel.org/pub/scm/linux/kernel/git/deller/linux-fbdev.git/commit/?h=for-next&id=bd771cf5c4254511cc4abb88f3dab3bd58bdf8e8

This patch fixes the crash in smtcfb_read(), but there is a similar
bug in smtcfb_write(), and I mocked up your patch a wrote a new patch
for it.
So we should fix two bugs with two patches.

Regards,
Zheyu Ma