On Thu, Apr 01, 2021 at 09:21:54AM +0300, Hassan Shahbazi wrote: > 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....@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.
Finding the root cause would be good to do here, so that we can potentially fix that if it is needed. thanks, greg k-h
