| Message ID | 1627293835-17441-2-git-send-email-zheyuma97@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Error out if 'pixclock' equals zero | expand |
Hi Zheyu, On Mon, Jul 26, 2021 at 12:04 PM Zheyu Ma <zheyuma97@gmail.com> wrote: > The userspace program could pass any values to the driver through > ioctl() interface. If the driver doesn't check the value of 'pixclock', > it may cause divide error. > > Fix this by checking whether 'pixclock' is zero first. > > The following log reveals it: > > [ 43.861711] divide error: 0000 [#1] PREEMPT SMP KASAN PTI > [ 43.861737] CPU: 2 PID: 11764 Comm: i740 Not tainted 5.14.0-rc2-00513-gac532c9bbcfb-dirty #224 > [ 43.861756] RIP: 0010:asiliantfb_check_var+0x4e/0x730 > [ 43.861843] Call Trace: > [ 43.861848] ? asiliantfb_remove+0x190/0x190 > [ 43.861858] fb_set_var+0x2e4/0xeb0 > [ 43.861866] ? fb_blank+0x1a0/0x1a0 > [ 43.861873] ? lock_acquire+0x1ef/0x530 > [ 43.861884] ? lock_release+0x810/0x810 > [ 43.861892] ? lock_is_held_type+0x100/0x140 > [ 43.861903] ? ___might_sleep+0x1ee/0x2d0 > [ 43.861914] ? __mutex_lock+0x620/0x1190 > [ 43.861921] ? do_fb_ioctl+0x313/0x700 > [ 43.861929] ? mutex_lock_io_nested+0xfa0/0xfa0 > [ 43.861936] ? __this_cpu_preempt_check+0x1d/0x30 > [ 43.861944] ? _raw_spin_unlock_irqrestore+0x46/0x60 > [ 43.861952] ? lockdep_hardirqs_on+0x59/0x100 > [ 43.861959] ? _raw_spin_unlock_irqrestore+0x46/0x60 > [ 43.861967] ? trace_hardirqs_on+0x6a/0x1c0 > [ 43.861978] do_fb_ioctl+0x31e/0x700 > > Signed-off-by: Zheyu Ma <zheyuma97@gmail.com> Thanks for your patch! > --- > Changes in v2: > - Make commit log more descriptive > --- > drivers/video/fbdev/asiliantfb.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/video/fbdev/asiliantfb.c b/drivers/video/fbdev/asiliantfb.c > index 3e006da47752..84c56f525889 100644 > --- a/drivers/video/fbdev/asiliantfb.c > +++ b/drivers/video/fbdev/asiliantfb.c > @@ -227,6 +227,9 @@ static int asiliantfb_check_var(struct fb_var_screeninfo *var, > { > unsigned long Ftarget, ratio, remainder; > > + if (!var->pixclock) > + return -EINVAL; While this fixes the crash, it is not correct: according to the fbdev API, invalid values must be rounded up to a supported value, if possible. -EINVAL should only be returned if rounding up values in fb_var_screeninfo cannot give a valid mode. The same comment applies to the other patches in this series: [PATCH v2 2/3] video: fbdev: kyro: Error out if 'pixclock' equals zero [PATCH v2 3/3] video: fbdev: riva: Error out if 'pixclock' equals zero > + > ratio = 1000000 / var->pixclock; > remainder = 1000000 % var->pixclock; > Ftarget = 1000000 * ratio + (1000000 * remainder) / var->pixclock; Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
diff --git a/drivers/video/fbdev/asiliantfb.c b/drivers/video/fbdev/asiliantfb.c index 3e006da47752..84c56f525889 100644 --- a/drivers/video/fbdev/asiliantfb.c +++ b/drivers/video/fbdev/asiliantfb.c @@ -227,6 +227,9 @@ static int asiliantfb_check_var(struct fb_var_screeninfo *var, { unsigned long Ftarget, ratio, remainder; + if (!var->pixclock) + return -EINVAL; + ratio = 1000000 / var->pixclock; remainder = 1000000 % var->pixclock; Ftarget = 1000000 * ratio + (1000000 * remainder) / var->pixclock;
The userspace program could pass any values to the driver through ioctl() interface. If the driver doesn't check the value of 'pixclock', it may cause divide error. Fix this by checking whether 'pixclock' is zero first. The following log reveals it: [ 43.861711] divide error: 0000 [#1] PREEMPT SMP KASAN PTI [ 43.861737] CPU: 2 PID: 11764 Comm: i740 Not tainted 5.14.0-rc2-00513-gac532c9bbcfb-dirty #224 [ 43.861756] RIP: 0010:asiliantfb_check_var+0x4e/0x730 [ 43.861843] Call Trace: [ 43.861848] ? asiliantfb_remove+0x190/0x190 [ 43.861858] fb_set_var+0x2e4/0xeb0 [ 43.861866] ? fb_blank+0x1a0/0x1a0 [ 43.861873] ? lock_acquire+0x1ef/0x530 [ 43.861884] ? lock_release+0x810/0x810 [ 43.861892] ? lock_is_held_type+0x100/0x140 [ 43.861903] ? ___might_sleep+0x1ee/0x2d0 [ 43.861914] ? __mutex_lock+0x620/0x1190 [ 43.861921] ? do_fb_ioctl+0x313/0x700 [ 43.861929] ? mutex_lock_io_nested+0xfa0/0xfa0 [ 43.861936] ? __this_cpu_preempt_check+0x1d/0x30 [ 43.861944] ? _raw_spin_unlock_irqrestore+0x46/0x60 [ 43.861952] ? lockdep_hardirqs_on+0x59/0x100 [ 43.861959] ? _raw_spin_unlock_irqrestore+0x46/0x60 [ 43.861967] ? trace_hardirqs_on+0x6a/0x1c0 [ 43.861978] do_fb_ioctl+0x31e/0x700 Signed-off-by: Zheyu Ma <zheyuma97@gmail.com> --- Changes in v2: - Make commit log more descriptive --- drivers/video/fbdev/asiliantfb.c | 3 +++ 1 file changed, 3 insertions(+)