From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> commit bd018a6a75cebb511bb55a0e7690024be975fe93 upstream. syzbot is reporting OOB read at vga_8planes_imageblit() [1], for "cdat[y] >> 4" can become a negative value due to "const char *cdat". [1] https://syzkaller.appspot.com/bug?id=0d7a0da1557dcd1989e00cb3692b26d4173b413... Reported-by: syzbot <syzbot+69fbd3e01470f169c8c4@syzkaller.appspotmail.com> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: stable <stable@vger.kernel.org> Link: https://lore.kernel.org/r/90b55ec3-d5b0-3307-9f7c-7ff5c5fd6ad3@i-love.sakura... Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- drivers/video/fbdev/vga16fb.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/video/fbdev/vga16fb.c b/drivers/video/fbdev/vga16fb.c index 2c6a576ed84c..4b83109202b1 100644 --- a/drivers/video/fbdev/vga16fb.c +++ b/drivers/video/fbdev/vga16fb.c @@ -1121,7 +1121,7 @@ static void vga_8planes_imageblit(struct fb_info *info, const struct fb_image *i char oldop = setop(0); char oldsr = setsr(0); char oldmask = selectmask(); - const char *cdat = image->data; + const unsigned char *cdat = image->data; u32 dx = image->dx; char __iomem *where; int y; -- 2.25.1