From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 3853B4DA9AF; Fri, 9 Oct 2026 14:22:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791555758; cv=none; b=ZiGkVY56kQi8+IRPJj5qXC2eIJsa/ONFkvq0EF+2K2Vdb2uGQCDpCeur0ZFQf+n6UgdPlZwv+rfdIwGwkxpjKaA8MvF1zZIOwy5LNc0mX3bUSSu/FwUIXJUmsfR+yBp7lzCRY7fX7D8k+ZxqgGKM2m/jS9tLB3B2PBfSQZmBn2M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791555758; c=relaxed/simple; bh=QhZVyVN3fxzVTs9ooi8/HUfgnH7L4itA73bpMrigg84=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=svKZhZ4Q4ILycqZq7AnbfWVBw/oMQAN4qJvFWZ7iBEcsPtO11ds4GTPVL9SwM3vR3swNbrVT1gNsMwV2Zy+daHpZlB+DV6SdaMU72qt89qwwincskQguj9SyAPpXTHQsk9AT/hfzitYyCGvdPvUfM5RdAJxIEuP9GDR4LmvtUIg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=nfofcgb2; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="nfofcgb2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 64AF01F00893; Fri, 9 Oct 2026 14:22:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1791555757; bh=E+llPs//mGnoKkjTOuYhCNmGw7ly6LeHBgHNedTDmX0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=nfofcgb2MjZsHJJImeYp2csopRLXStHqZ3MHQOImziJU2rVmCbCKDzrssvt7lO8E1 BmFlutoA5+ab7bV2tzT6QZnQaJIRtYJSQk6QRSHUUDtJmeeW5FoKz8aDmKiaK+o/Si nZXzTtXLrmA/O8jgknwC5bV/Pi9jsixyJqH5kgIQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable , Zizhi Wo Subject: [PATCH 7.2 060/428] vt: skip screen update for DEC alignment test on backgroup consoles Date: Fri, 9 Oct 2026 16:06:37 +0200 Message-ID: <20261009140947.458652311@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261009140946.008206689@linuxfoundation.org> References: <20261009140946.008206689@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 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Zizhi Wo commit 0928ed9bd7946baee911efa401088697836e3b1e upstream. [BUG] Recently, we encountered a KASAN warning as follows: BUG: KASAN: slab-out-of-bounds in fb_pad_aligned_buffer+0x11f/0x140 Read of size 1 at addr ff1100015fd9f6a4 by task tty_fbcon_oob/1239 CPU: 7 UID: 0 PID: 1239 Comm: tty_fbcon_oob Not tainted 7.3.0-rc1 #100 PREEMPT(full) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014 Call Trace: ... kasan_report+0xf0/0x120 fb_pad_aligned_buffer+0x11f/0x140 ccw_putcs+0x86c/0xa80 fbcon_putcs+0x338/0x410 do_update_region+0x21d/0x450 do_con_write+0x1e0e/0x4880 con_write+0x13/0x80 n_tty_write+0x374/0x1010 file_tty_write.isra.0+0x404/0x7a0 ... reproduce: 1) open /dev/tty0, set a KDFONTOP ioctl with op.op = KD_FONT_OP_SET, op.width = 8 and op.height = 16 (visible VC1) 2) open /dev/tty1, set a KDFONTOP ioctl with op.op = KD_FONT_OP_SET, op.width = 28 and op.height = 24 (invisible VC2) 3) echo 3 > /sys/devices/virtual/graphics/fbcon/rotate_all 4) write EShash8(esc hash8) to tty1 [CAUSE] All VCs render to the framebuffer. setfont only modifies the target VC's font without resizing the framebuffer backing buffer (par->rotated.buf); the buffer is only resized for the visible VC (fbcon_do_set_font -> ... -> vc_do_resize -> update_screen). This relies on the con_should_update() check performed before every update_region(). However, the ESC # 8 path (do_con_trol -> do_update_region) omits the con_should_update() check. After changing the font size of an invisible VC, do_update_region() fills using the new font size against a buffer that was never resized, causing an out-of-bounds access. [FIX] Only push the update when the console is visible and not blanked, add the con_should_update() check in the do_con_trol() like every other call site of do_update_region() (update_region(), invert_screen(), ...). Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable Signed-off-by: Zizhi Wo Link: https://patch.msgid.link/20260905064337.3083103-1-wozizhi@huaweicloud.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/vt/vt.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -2860,7 +2860,8 @@ static void do_con_trol(struct tty_struc csi_J(vc, CSI_J_VISIBLE); vc->vc_video_erase_char = (vc->vc_video_erase_char & 0xff00) | ' '; - do_update_region(vc, vc->vc_origin, vc->vc_screenbuf_size / 2); + if (con_should_update(vc)) + do_update_region(vc, vc->vc_origin, vc->vc_screenbuf_size / 2); } return; case ESsetG0: /* ESC ( */