Re: [PATCH 4.19] fbmem: add margin check to fb_check_caps()
From: Dongliang Mu <hidden>
Date: 2021-09-02 06:06:23
Also in:
dri-devel, lkml
On Thu, Sep 2, 2021 at 2:02 PM Dongliang Mu [off-list ref] wrote:
[ Upstream commit a49145acfb975d921464b84fe00279f99827d816 ] 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. Note that, this patch needs special handling to backport it to linux kernel 4.19, 4.14, 4.9, 4.4.
I have tested that, this patch can be applied to the branches: linux-4.19.y/linux-4.14.y/linux-4.9.y/linux-4.4.y.
quoted hunk ↗ jump to hunk
Signed-off-by: George Kennedy <redacted> Reported-by: syzbot+e5fd3e65515b48c02a30@syzkaller.appspotmail.com Reviewed-by: Dan Carpenter <redacted> Cc: Dhaval Giani <redacted> Signed-off-by: Bartlomiej Zolnierkiewicz <redacted> Link: https://patchwork.freedesktop.org/patch/msgid/1594149963-13801-1-git-send-email-george.kennedy@oracle.com 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; + ret = info->fbops->fb_check_var(var, info); if (ret) --2.25.1