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Commit 4e96ee11 authored by Zhang Shurong's avatar Zhang Shurong Committed by Greg Kroah-Hartman
Browse files

fbdev: fix potential OOB read in fast_imageblit() 

[ Upstream commit c2d22806aecb24e2de55c30a06e5d6eb297d161d ]

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: default avatarZhang Shurong <zhang_shurong@foxmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarHelge Deller <deller@gmx.de>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent ebf84320

drivers/video/fbdev/core/sysimgblt.c

+1 −1
Original line number Diff line number Diff line
@@ -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;