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 813EB360EDC for ; Thu, 2 Jul 2026 13:52:32 +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=1783000353; cv=none; b=qnnFKA03xAN+uMkkYJx3Uu0E+zrG1ivt4h8tGRkF/pkqVzPBJJ/7BnsTyIGQIHjbpehyOX3rGh9GTovmqEbRMKiL3/Uziza6ryG964SFWooDuh9+26sXTVQ480FMy2VIHICCAKUSnYiVhVcizfYTPTllhYBHj6A7N/puweoxt3k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783000353; c=relaxed/simple; bh=j/UDqIB8kkju/Mc3RqVh5qBDliywmf8SBbiGagEL6DU=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=MRo0Bo1ZytmuL8avaFFACztQdaC/KV8vGu+MJsTl4saaQ5stLyItWgfiKt+kpWiThxM+lqvh0xN0m6sY7SPmZQc2J84TGTdyLjp39YEIuVM/FSnn8DTWJkhZV5Hkh1lFOeQJucEWP2ERS0VbBEug+S+U4ydNVzePL+M9N/B4K4I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=c6LMbmXN; 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="c6LMbmXN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A15251F000E9; Thu, 2 Jul 2026 13:52:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1783000352; bh=E5R8BHEOibtT6FTrZyuY+qdj53L6Px6ujqmJXDVoggo=; h=Subject:To:Cc:From:Date; b=c6LMbmXNOaswqJi7sfabWpyo5kbgBzI5Aw+QP8im+T0RWp+9kCeu0URahwtP59O6B ZprJ1KWOt0wN0TNVQ7c6ehzDyImtmCRo0kBtLDvf8BzOvheEcluZvmg+84VDXGujF9 0i0VpHjGFemXha+0nKsNtXwq3dw2E5QdxowAkWlY= Subject: FAILED: patch "[PATCH] fbdev: fbcon: fix out-of-bounds read in err_out of" failed to apply to 5.15-stable tree To: 25181214217@stu.xidian.edu.cn,deller@gmx.de,tzimmermann@suse.de Cc: From: Date: Thu, 02 Jul 2026 15:52:30 +0200 Message-ID: <2026070230-congrats-plenty-c9d5@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 8fdc8c2057eea08d40ce2c8eed41ff9e451c65c2 # git commit -s git send-email --to '' --in-reply-to '2026070230-congrats-plenty-c9d5@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 8fdc8c2057eea08d40ce2c8eed41ff9e451c65c2 Mon Sep 17 00:00:00 2001 From: Mingyu Wang <25181214217@stu.xidian.edu.cn> Date: Fri, 26 Jun 2026 00:03:06 +0800 Subject: [PATCH] fbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font() When fbcon_do_set_font() fails (e.g., due to a memory allocation failure inside vc_resize() under heavy memory pressure), it jumps to the `err_out` label to roll back the console state. However, the current rollback logic forgets to restore the `hi_font` state, leading to a severe state machine corruption. Earlier in the function, `set_vc_hi_font()` might be called to change `vc->vc_hi_font_mask` and mutate the screen buffer. If `vc_resize()` subsequently fails, the `err_out` path restores `vc_font.charcount` but entirely skips rolling back the `vc_hi_font_mask` and the screen buffer. This mismatch leaves the terminal in a desynchronized state. Because `vc_hi_font_mask` remains set, the VT subsystem will still accept character indices greater than 255 from userspace and write them to the screen buffer. Subsequent rendering calls (e.g., `fbcon_putcs()`) will then use these inflated indices to access the reverted, 256-character font array, leading to a deterministic out-of-bounds read and potential kernel memory disclosure. Fix this by adding the missing rollback logic for the `hi_font` mask and screen buffer in the error path. Fixes: a5a923038d70 ("fbdev: fbcon: Properly revert changes when vc_resize() failed") Cc: stable@vger.kernel.org Signed-off-by: Mingyu Wang <25181214217@stu.xidian.edu.cn> Reviewed-by: Thomas Zimmermann Signed-off-by: Helge Deller diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 9077d3b99357..37beb93045af 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2405,6 +2405,7 @@ static int fbcon_do_set_font(struct vc_data *vc, int w, int h, int charcount, int resize, ret, old_width, old_height, old_charcount; font_data_t *old_fontdata = p->fontdata; const u8 *old_data = vc->vc_font.data; + unsigned short old_hi_font_mask = vc->vc_hi_font_mask; font_data_get(data); @@ -2451,6 +2452,12 @@ static int fbcon_do_set_font(struct vc_data *vc, int w, int h, int charcount, vc->vc_font.height = old_height; vc->vc_font.charcount = old_charcount; + /* Restore the hi_font state and screen buffer */ + if (old_hi_font_mask && !vc->vc_hi_font_mask) + set_vc_hi_font(vc, true); + else if (!old_hi_font_mask && vc->vc_hi_font_mask) + set_vc_hi_font(vc, false); + font_data_put(data); return ret;