Hi Dongliang, On Thu, Sep 2, 2021 at 8:04 AM Dongliang Mu <mudongliangabcd@xxxxxxxxx> wrote: > [ Upstream commit a49145acfb975d921464b84fe00279f99827d816 ] Oops, looks like I missed when that one was submitted for review... > A fb_ioctl() FBIOPUT_VSCREENINFO call with invalid xres setting > or yres setting in struct fb_var_screeninfo will result in a > KASAN: vmalloc-out-of-bounds failure in bitfill_aligned() as > the margins are being cleared. The margins are cleared in > chunks and if the xres setting or yres setting is a value of > zero upto the chunk size, the failure will occur. > > Add a margin check to validate xres and yres settings. Shouldn't (the caller of) bitfill_aligned() be fixed instead? Can this be triggered by e.g. using the mini_4x6 font? > Note that, this patch needs special handling to backport it to linux > kernel 4.19, 4.14, 4.9, 4.4. > > Signed-off-by: George Kennedy <george.kennedy@xxxxxxxxxx> > Reported-by: syzbot+e5fd3e65515b48c02a30@xxxxxxxxxxxxxxxxxxxxxxxxx > Reviewed-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> > Cc: Dhaval Giani <dhaval.giani@xxxxxxxxxx> > Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@xxxxxxxxxxx> > Link: https://patchwork.freedesktop.org/patch/msgid/1594149963-13801-1-git-send-email-george.kennedy@xxxxxxxxxx > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> > --- > drivers/video/fbdev/core/fbmem.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c > index 84845275dbef..de04c097d67c 100644 > --- a/drivers/video/fbdev/core/fbmem.c > +++ b/drivers/video/fbdev/core/fbmem.c > @@ -991,6 +991,10 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var) > goto done; > } > > + /* bitfill_aligned() assumes that it's at least 8x8 */ > + if (var->xres < 8 || var->yres < 8) > + return -EINVAL; Are you sure there don't exist such small displays (e.g. OLED)? > + > ret = info->fbops->fb_check_var(var, info); > > if (ret) Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx 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
