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 E3EB64A3415 for ; Thu, 2 Jul 2026 13:52:34 +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=1783000356; cv=none; b=lWPe9pkzuOo6sJC19ZV58XKqhCRDFfxdeYc+xDwwabbo3qQ4Hj41vJdrSS40xq136Khtn8mTIJXywFM9w1EKH5dE8Z81q8327HKa7QkXtGfLr97HOYbABoAW1SLmHGcId4xbyBhQFyzCZ6x950K4MHrPUdSI1q3seJbU2CWa550= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783000356; c=relaxed/simple; bh=iqoRMYKFTxlh+lj1sDOwmYmk9CpE4HrZxY84RTxbZYo=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=WAzQk8+tR5e5JMfIMs4CTOKx9kN9/AD6HDVzkOOFMZGeP/uECuQvf52BDOZHMEkLUy1io3SMes8+gXogevzwHaX6y+bmyjkAmr59MzUubdCp2A2tyG8smCe9rvDdtARmFRhw1VnNpv2VQHoQ0UzR3G9ZurkRjNsXpmbFcZ6Ryog= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=CmXuv1Zx; 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="CmXuv1Zx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 330E41F000E9; Thu, 2 Jul 2026 13:52:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1783000354; bh=nhbtCgzMK0a9b9ABlJHvPScEnUOJgaG7qSuUm1Cpxso=; h=Subject:To:Cc:From:Date; b=CmXuv1ZxaS72dWrDi5Fx9lT0x5r9/+Y3FMR0iKqqk6bnuzRYUqgHnVlC4kc2B82yb 4OaY8fwy0eSDyyjEDvjZrNLUIFWjqBeagsXNRtv9Yd6IjQXw8+pOLHekchEPb1rawM +pnm5+YgkKSjvQU9G9pWf5YQgeG9kWBqvnql5fkg= Subject: FAILED: patch "[PATCH] fbdev: fbcon: fix out-of-bounds read in err_out of" failed to apply to 6.6-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-citrus-unboxed-57bc@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 6.6-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-6.6.y git checkout FETCH_HEAD git cherry-pick -x 8fdc8c2057eea08d40ce2c8eed41ff9e451c65c2 # git commit -s git send-email --to '' --in-reply-to '2026070230-citrus-unboxed-57bc@gregkh' --subject-prefix 'PATCH 6.6.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;