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fbmem: add margin check to fb_check_caps()

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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.

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-email-george.kennedy@oracle.com
This commit is contained in:
George Kennedy 2020-07-07 15:26:03 -04:00 committed by Bartlomiej Zolnierkiewicz
parent 54d04ea8cd
commit a49145acfb
1 changed files with 4 additions and 0 deletions
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4
drivers/video/fbdev/core/fbmem.c
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@ -1006,6 +1006,10 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
return 0;
}
/* 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)