The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.14.y git checkout FETCH_HEAD git cherry-pick -x c2d22806aecb24e2de55c30a06e5d6eb297d161d # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023062901-public-account-117e@gregkh' --subject-prefix 'PATCH 4.14.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From c2d22806aecb24e2de55c30a06e5d6eb297d161d Mon Sep 17 00:00:00 2001 From: Zhang Shurong zhang_shurong@foxmail.com Date: Sun, 25 Jun 2023 00:16:49 +0800 Subject: [PATCH] fbdev: fix potential OOB read in fast_imageblit()

There is a potential OOB read at fast_imageblit, for "colortab[(*src >> 4)]" can become a negative value due to "const char *s = image->data, *src". This change makes sure the index for colortab always positive or zero.

Similar commit: https://patchwork.kernel.org/patch/11746067

Potential bug report: https://groups.google.com/g/syzkaller-bugs/c/9ubBXKeKXf4/m/k-QXy4UgAAAJ

Signed-off-by: Zhang Shurong zhang_shurong@foxmail.com Cc: stable@vger.kernel.org Signed-off-by: Helge Deller deller@gmx.de

diff --git a/drivers/video/fbdev/core/sysimgblt.c b/drivers/video/fbdev/core/sysimgblt.c index 335e92b813fc..665ef7a0a249 100644 --- a/drivers/video/fbdev/core/sysimgblt.c +++ b/drivers/video/fbdev/core/sysimgblt.c @@ -189,7 +189,7 @@ static void fast_imageblit(const struct fb_image *image, struct fb_info *p, u32 fgx = fgcolor, bgx = bgcolor, bpp = p->var.bits_per_pixel; u32 ppw = 32/bpp, spitch = (image->width + 7)/8; u32 bit_mask, eorx, shift; - const char *s = image->data, *src; + const u8 *s = image->data, *src; u32 *dst; const u32 *tab; size_t tablen;