From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E9AA44C97; Tue, 11 Nov 2025 00:48:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762822093; cv=none; b=W0Z4dnNja/w4IbDOYBUQO4DU4RIsvk0lMWUuJiG6Q4ImuOeUqoR/8PLDQXBXnHIcSbXtEjIxqhP3nri2UZPG4F4dTopp5o8uTcrkYYYgIfzK6VumN6rzJWRsxKoHQzBCJCVGYLydcDU04fMPvpBQfdpQArMEDkawvLN/BOQSUto= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762822093; c=relaxed/simple; bh=KnYJiYTZjG42VqUhEvhftKkTQxHfl9GTYHYjDsi18Tc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PLob2CkYNkoXWqyzIlOYAiV6yX+ui8xENT+CBnlEsCA04q6QqlTPLA+koN+44yegQu4JWhdE8TZT47JSKY6Nffjh2opZRqmbelRCwA6hur1qle/vnakriEWE7XruL+v6MOpdzz6PKqkWyUh9YOgyE4RODVvCHpyk10fnkCmcnGo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Q6WBlq2e; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Q6WBlq2e" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 56EA0C19424; Tue, 11 Nov 2025 00:48:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1762822092; bh=KnYJiYTZjG42VqUhEvhftKkTQxHfl9GTYHYjDsi18Tc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Q6WBlq2esXNmFWusFykHd4CJD7uPYVKersya7oOY//neC15XybSND425Is3GyRqeU ntkH5WE1jTn9y7WGr8bPNXn+PNdUdoiK4Ir12wonSG4fUC10+0S/Nbha9k6PR6elm+ HL6gIC2wryB4b7vLBfNxDy41QTdbD0gbLvdHHWSU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+793cf822d213be1a74f2@syzkaller.appspotmail.com, Junjie Cao , Thomas Zimmermann , Helge Deller Subject: [PATCH 6.17 014/849] fbdev: bitblit: bound-check glyph index in bit_putcs* Date: Tue, 11 Nov 2025 09:33:04 +0900 Message-ID: <20251111004536.808055651@linuxfoundation.org> X-Mailer: git-send-email 2.51.2 In-Reply-To: <20251111004536.460310036@linuxfoundation.org> References: <20251111004536.460310036@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Junjie Cao 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 --- drivers/video/fbdev/core/bitblit.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) --- a/drivers/video/fbdev/core/bitblit.c +++ b/drivers/video/fbdev/core/bitblit.c @@ -79,12 +79,16 @@ static inline void bit_putcs_aligned(str 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); @@ -112,14 +116,18 @@ static inline void bit_putcs_unaligned(s 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);