From nobody Sat Feb 7 17:41:35 2026 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.11]) (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 C2DD824DD17; Mon, 20 Oct 2025 13:06:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.11 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760965589; cv=none; b=TFl0ECKHv6ypoG0YWLaSkTMxyZcAon7PM+S1wYkGlOkTcx69cMW31caNdUpCGGLTB7SvCZHdbXXaLlo4VISkGNV8DAT699cEs2HT+Udfyy9pLGfT5SA/lj8++FOFL/GeeIJU6YE5vYksOV639bS3pbACXqCMLkCqP8iVk4mO9m0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760965589; c=relaxed/simple; bh=wAI0xMkSnbhaSLTqgomUxHh2ZZalda3QNhhiLBoAQgI=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=VIIN0guhjQMoH0Dg1/yCLX6GUBA0y0UBtRf8yCyy5JXj0gB9qwFdFhzbaeXzCkeafeWP0MHi24FLzzxAv6RFdLJa4/3647wJmAPmOgk3oSG7Q9zTCYTS33igjb39W5QNCozzlbPLsiuLb4LxpQL0CGoyb3g2Ae4RdQst7zEFqNs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=aUxq3ede; arc=none smtp.client-ip=192.198.163.11 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="aUxq3ede" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1760965587; x=1792501587; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=wAI0xMkSnbhaSLTqgomUxHh2ZZalda3QNhhiLBoAQgI=; b=aUxq3edeRNAiYfzGnjCIPNJocVleiV2U92xXwFtAr6bjphM/ttvd4qRO fOwLc2MJqP8h4IUt9VW4DlccO38/BsXCRk1FXlhERYsck1TFSK3dS08fl T7vsK8L3+ablt93YqZI6/bDVuCdUlCP60FPFGmma9eM470+Ni4IwU3DHd +aK8m0LatK8BZtLRDocrOYy9cQgppMHzkhkf6p++cUW8VMxzGe/HzN0o1 Udq/9llY/b1P1x+EM5mQ02thMe2xLY7bM8QARxNBuB5M6qVkWxi9y5Axe t/DeRUzXnHdcaViMOyTN8GW5HbE3eFkyCuHrGKUg5V9itZNmCwIUMzF1b w==; X-CSE-ConnectionGUID: 6eHXMC+1Sk6YBjzrnG5Suw== X-CSE-MsgGUID: ns2Ibpp2Q+OSoIuDXKTEVA== X-IronPort-AV: E=McAfee;i="6800,10657,11586"; a="73684702" X-IronPort-AV: E=Sophos;i="6.19,242,1754982000"; d="scan'208";a="73684702" Received: from orviesa004.jf.intel.com ([10.64.159.144]) by fmvoesa105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Oct 2025 06:06:26 -0700 X-CSE-ConnectionGUID: 1WMr52nHQFe+l2MAr15/QQ== X-CSE-MsgGUID: DHmPvODTREu8wI8w65VIxg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.19,242,1754982000"; d="scan'208";a="187583943" Received: from b580.bj.intel.com ([10.238.152.130]) by orviesa004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Oct 2025 06:06:23 -0700 From: Junjie Cao To: Thomas Zimmermann , Simona Vetter , Helge Deller , Zsolt Kajtar Cc: Albin Babu Varghese , linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, Junjie Cao , syzbot+793cf822d213be1a74f2@syzkaller.appspotmail.com Subject: [PATCH v2] fbdev: bitblit: bound-check glyph index in bit_putcs* Date: Mon, 20 Oct 2025 21:47:01 +0800 Message-ID: <20251020134701.84082-1-junjie.cao@intel.com> X-Mailer: git-send-email 2.48.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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=3D793cf822d213be1a74f2 Tested-by: syzbot+793cf822d213be1a74f2@syzkaller.appspotmail.com Signed-off-by: Junjie Cao Reviewed-by: Thomas Zimmermann --- v1: https://lore.kernel.org/linux-fbdev/5d237d1a-a528-4205-a4d8-71709134f1e= 1@suse.de/ v1 -> v2: - Fix indentation and add blank line after declarations with the .pl helper - No functional changes 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 9d2e59796c3e..085ffb44c51a 100644 --- a/drivers/video/fbdev/core/bitblit.c +++ b/drivers/video/fbdev/core/bitblit.c @@ -79,12 +79,16 @@ static inline void bit_putcs_aligned(struct vc_data *vc= , struct fb_info *info, struct fb_image *image, u8 *buf, u8 *dst) { u16 charmask =3D vc->vc_hi_font_mask ? 0x1ff : 0xff; + unsigned int charcnt =3D vc->vc_font.charcount; u32 idx =3D vc->vc_font.width >> 3; u8 *src; =20 while (cnt--) { - src =3D vc->vc_font.data + (scr_readw(s++)& - charmask)*cellsize; + u16 ch =3D scr_readw(s++) & charmask; + + if (ch >=3D charcnt) + ch =3D 0; + src =3D vc->vc_font.data + (unsigned int)ch * cellsize; =20 if (attr) { update_attr(buf, src, attr, vc); @@ -112,14 +116,18 @@ static inline void bit_putcs_unaligned(struct vc_data= *vc, u8 *dst) { u16 charmask =3D vc->vc_hi_font_mask ? 0x1ff : 0xff; + unsigned int charcnt =3D vc->vc_font.charcount; u32 shift_low =3D 0, mod =3D vc->vc_font.width % 8; u32 shift_high =3D 8; u32 idx =3D vc->vc_font.width >> 3; u8 *src; =20 while (cnt--) { - src =3D vc->vc_font.data + (scr_readw(s++)& - charmask)*cellsize; + u16 ch =3D scr_readw(s++) & charmask; + + if (ch >=3D charcnt) + ch =3D 0; + src =3D vc->vc_font.data + (unsigned int)ch * cellsize; =20 if (attr) { update_attr(buf, src, attr, vc); --=20 2.48.1