| Message ID | 20220404084723.79089-8-zheyuma97@gmail.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Headers | show |
| Series | Fix divide errors in fbdev drivers | expand |
On Mon, Apr 4, 2022 at 3:50 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 in s3fb_check_var(). > > The following log reveals it: > > [ 511.141561] divide error: 0000 [#1] PREEMPT SMP KASAN PTI > [ 511.141607] RIP: 0010:s3fb_check_var+0x3f3/0x530 > [ 511.141693] Call Trace: > [ 511.141695] <TASK> > [ 511.141716] fb_set_var+0x367/0xeb0 > [ 511.141815] do_fb_ioctl+0x234/0x670 > [ 511.141876] fb_ioctl+0xdd/0x130 > [ 511.141888] do_syscall_64+0x3b/0x90 > > Signed-off-by: Zheyu Ma <zheyuma97@gmail.com> > --- > drivers/video/fbdev/s3fb.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/video/fbdev/s3fb.c b/drivers/video/fbdev/s3fb.c > index 5c74253e7b2c..b93c8eb02336 100644 > --- a/drivers/video/fbdev/s3fb.c > +++ b/drivers/video/fbdev/s3fb.c > @@ -549,6 +549,9 @@ static int s3fb_check_var(struct fb_var_screeninfo *var, struct fb_info *info) > int rv, mem, step; > u16 m, n, r; > > + if (!var->pixclock) > + return -EINVAL; > + When passed an invalid value, .check_var() is supposed to round up the invalid value to a valid value, if possible. > /* Find appropriate format */ > rv = svga_match_format (s3fb_formats, var, NULL); 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/s3fb.c b/drivers/video/fbdev/s3fb.c index 5c74253e7b2c..b93c8eb02336 100644 --- a/drivers/video/fbdev/s3fb.c +++ b/drivers/video/fbdev/s3fb.c @@ -549,6 +549,9 @@ static int s3fb_check_var(struct fb_var_screeninfo *var, struct fb_info *info) int rv, mem, step; u16 m, n, r; + if (!var->pixclock) + return -EINVAL; + /* Find appropriate format */ rv = svga_match_format (s3fb_formats, var, NULL);
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 in s3fb_check_var(). The following log reveals it: [ 511.141561] divide error: 0000 [#1] PREEMPT SMP KASAN PTI [ 511.141607] RIP: 0010:s3fb_check_var+0x3f3/0x530 [ 511.141693] Call Trace: [ 511.141695] <TASK> [ 511.141716] fb_set_var+0x367/0xeb0 [ 511.141815] do_fb_ioctl+0x234/0x670 [ 511.141876] fb_ioctl+0xdd/0x130 [ 511.141888] do_syscall_64+0x3b/0x90 Signed-off-by: Zheyu Ma <zheyuma97@gmail.com> --- drivers/video/fbdev/s3fb.c | 3 +++ 1 file changed, 3 insertions(+)