On Thu, Sep 2, 2021 at 9:15 PM Geert Uytterhoeven geert@linux-m68k.org wrote:
Hi Dongliang,
On Thu, Sep 2, 2021 at 8:04 AM Dongliang Mu mudongliangabcd@gmail.com wrote:
[ Upstream commit a49145acfb975d921464b84fe00279f99827d816 ]
Oops, looks like I missed when that one was submitted for review...
This patch cannot directly apply to old stable trees. Maybe that's the reason.
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?
I am sorry. I don't know much detail about this subsystem. I just found syzkaller can still trigger this bug in linux-4.19.
Combined with the bug information, I found this patch is not merged into the old kernel trees. So I send this patch rebased on linux-4.19. Also I have tested it on linux-4.14 and below.
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@oracle.com Reported-by: syzbot+e5fd3e65515b48c02a30@syzkaller.appspotmail.com Reviewed-by: Dan Carpenter dan.carpenter@oracle.com Cc: Dhaval Giani dhaval.giani@oracle.com Signed-off-by: Bartlomiej Zolnierkiewicz b.zolnierkie@samsung.com Link: https://patchwork.freedesktop.org/patch/msgid/1594149963-13801-1-git-send-em... Signed-off-by: Sasha Levin sashal@kernel.org
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@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