From: Hassan Shahbazi <h.shahbazi.git@gmail.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: daniel.vetter@ffwll.ch, jirislaby@kernel.org,
yepeilin.cs@gmail.com, linux-fbdev@vger.kernel.org,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
h.shahbazi.git@gmail.com
Subject: Re: [PATCH] fix NULL pointer deference crash
Date: Thu, 1 Apr 2021 09:21:54 +0300 [thread overview]
Message-ID: <20210401062154.5evjajj64r4tjseh@gentoo> (raw)
In-Reply-To: <YGSyFgeNd7gfsbR6@kroah.com>
On Wed, Mar 31, 2021 at 07:32:06PM +0200, Greg KH wrote:
> On Wed, Mar 31, 2021 at 07:34:29PM +0300, Hassan Shahbazi wrote:
> > The patch has fixed a NULL pointer deference crash in hiding the cursor. It
> > is verified by syzbot patch tester.
> >
> > Reported by: syzbot
> > https://syzkaller.appspot.com/bug?id=defb47bf56e1c14d5687280c7bb91ce7b608b94b
> >
> > Signed-off-by: Hassan Shahbazi <h.shahbazi.git@gmail.com>
> > ---
> > drivers/video/fbdev/core/fbcon.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> > index 44a5cd2f54cc..ee252d1c43c6 100644
> > --- a/drivers/video/fbdev/core/fbcon.c
> > +++ b/drivers/video/fbdev/core/fbcon.c
> > @@ -1333,8 +1333,9 @@ static void fbcon_cursor(struct vc_data *vc, int mode)
> >
> > ops->cursor_flash = (mode == CM_ERASE) ? 0 : 1;
> >
> > - ops->cursor(vc, info, mode, get_color(vc, info, c, 1),
> > - get_color(vc, info, c, 0));
> > + if (ops && ops->cursor)
>
> As ops obviously is not NULL here (you just used it on the line above),
> why are you checking it again?
Yes, that's right. I will remove that check and will submit a new patch.
> And what makes curser be NULL here? How can that happen?
Honestly, I don't know. I reproduced the crash on my local, followed the
stack trace, and then changed the line to avoid the crash. If you think this
patch is not the best solution, I can drop it and investigate more to find
the root cause.
> Also your subject line can use some work, please make it reflect the
> driver subsystem you are looking at.
This was a mistake, I did not intend to change the subject. I will ensure
the next patch reflects the subsystem.
> thanks,
>
> greg k-h
Best,
Hassan Shahbazi
next prev parent reply other threads:[~2021-04-01 6:22 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-31 16:34 [PATCH] fix NULL pointer deference crash Hassan Shahbazi
2021-03-31 17:32 ` Greg KH
2021-04-01 6:21 ` Hassan Shahbazi [this message]
2021-04-01 6:54 ` Greg KH
2021-03-31 20:02 ` Dan Carpenter
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