From 3e9e3250f847b1a14892070446f0aefac1616087 Mon Sep 17 00:00:00 2001 From: Junjie Cao Date: Thu, 11 Dec 2025 11:30:09 +0000 Subject: [PATCH] fbdev: bitblit: bound-check glyph index in bit_putcs* stable inclusion from stable-v6.6.117 commit 9ba1a7802ca9a2590cef95b253e6526f4364477f category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IDBAJ2 CVE: CVE-2025-40322 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9ba1a7802ca9a2590cef95b253e6526f4364477f ---------------------------------------------------------------------- commit 18c4ef4e765a798b47980555ed665d78b71aeadf upstream. bit_putcs_aligned()/unaligned() derived the glyph pointer from the character value masked by 0xff/0x1ff, which may exceed the actual font's glyph count and read past the end of the built-in font array. Clamp the index to the actual glyph count before computing the address. This fixes a global out-of-bounds read reported by syzbot. Reported-by: syzbot+793cf822d213be1a74f2@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=793cf822d213be1a74f2 Tested-by: syzbot+793cf822d213be1a74f2@syzkaller.appspotmail.com Signed-off-by: Junjie Cao Reviewed-by: Thomas Zimmermann Signed-off-by: Helge Deller Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Luo Gengkun --- drivers/video/fbdev/core/bitblit.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/drivers/video/fbdev/core/bitblit.c b/drivers/video/fbdev/core/bitblit.c index 8587c9da0670..43639f045269 100644 --- a/drivers/video/fbdev/core/bitblit.c +++ b/drivers/video/fbdev/core/bitblit.c @@ -80,12 +80,16 @@ static inline void bit_putcs_aligned(struct vc_data *vc, struct fb_info *info, struct fb_image *image, u8 *buf, u8 *dst) { u16 charmask = vc->vc_hi_font_mask ? 0x1ff : 0xff; + unsigned int charcnt = vc->vc_font.charcount; u32 idx = vc->vc_font.width >> 3; u8 *src; while (cnt--) { - src = vc->vc_font.data + (scr_readw(s++)& - charmask)*cellsize; + u16 ch = scr_readw(s++) & charmask; + + if (ch >= charcnt) + ch = 0; + src = vc->vc_font.data + (unsigned int)ch * cellsize; if (attr) { update_attr(buf, src, attr, vc); @@ -113,14 +117,18 @@ static inline void bit_putcs_unaligned(struct vc_data *vc, u8 *dst) { u16 charmask = vc->vc_hi_font_mask ? 0x1ff : 0xff; + unsigned int charcnt = vc->vc_font.charcount; u32 shift_low = 0, mod = vc->vc_font.width % 8; u32 shift_high = 8; u32 idx = vc->vc_font.width >> 3; u8 *src; while (cnt--) { - src = vc->vc_font.data + (scr_readw(s++)& - charmask)*cellsize; + u16 ch = scr_readw(s++) & charmask; + + if (ch >= charcnt) + ch = 0; + src = vc->vc_font.data + (unsigned int)ch * cellsize; if (attr) { update_attr(buf, src, attr, vc); -- Gitee