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 5A6E3308F13; Mon, 1 Dec 2025 11:25:40 +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=1764588340; cv=none; b=cu7zF+rwNcsOZnSY9d1kmj9szkmAxLq+bM+s9IjOpMYU08PxOS/1A3SLDW+MzlDL9oMylizG2l3nSbj6vQ0pibk/IIO1alTS33lBLmkHKXh1jiG3J28ksFcOKb16RXjbE6uPoQZBA0FGPWjSTP4IX+xCiA0myYY3dXmPEryv+s8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764588340; c=relaxed/simple; bh=CPDMRrq2omHs54/Gl95i22yNrP9ftOn7XCPeuvVTtzY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Xl9wJLrnOKiWWuUiecED+/fuboIrF26tQ7Pqvx2BDjyBIuL3jy0KMC3Kh9wobHAoWj+BiM6kNaEuJMHm14wseuIRuHhItKT21apZ6motDigW1VzcSRMIakqD+KGgHLzgTXREOj3XewlzlaYhkreV45M9Ny7NovDHZP2LouIpejs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=sb+o1CqY; 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="sb+o1CqY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D02F2C4CEF1; Mon, 1 Dec 2025 11:25:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1764588340; bh=CPDMRrq2omHs54/Gl95i22yNrP9ftOn7XCPeuvVTtzY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sb+o1CqYnNmKNczYKd6QP9zK4CLFgal5bPaUUWbAQTb7A6wAr21iJHXaX5dFR45aS SBtp8ZFR/F+FkUuq+h4rUMf2ASMJIe5PQ6oZTnXV6k1+qReDuxPv2RoIskxJ8HebfU G/XGou6RwHJzgHO6AMC+7+Y3bmkfOHKWOA6uGEas= 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 5.4 007/187] fbdev: bitblit: bound-check glyph index in bit_putcs* Date: Mon, 1 Dec 2025 12:21:55 +0100 Message-ID: <20251201112241.514504365@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251201112241.242614045@linuxfoundation.org> References: <20251201112241.242614045@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.4-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 @@ -80,12 +80,16 @@ 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); @@ -113,14 +117,18 @@ 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);