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 44DF93BCD05; Thu, 16 Jul 2026 13:59:26 +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=1784210367; cv=none; b=gyLfDji+YI/HKv6SsLVt09E6hXRpJNtqvpRX4tOopF7TFileB/yYY2jQt4O7Ds6c9GG/Z+Zn1av2aSzssu8EE8ZWSpi/8Gdu3EAgqNKVBBiUTrLzPDAMT7OO+Pzk+FgxkJIjFGgdFRiuO5BrhVktwC99QYgeI8pMvcsKRL7C5Sw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784210367; c=relaxed/simple; bh=KjWsvP+wki/0tEu3s8OImJMbbGoaZ4xHnXFNLXwWkYM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=KBhk4FoTjkW7U75/Xzu19P0/0bA46Xj+n07TthV96CqcbUArsPrdMZbOq16j1wuYExGaSGdZp9x+S+ecLbu8nIimEbFduZF085FZYT0GJWDnqkO7j/we4RJVUGW7GM4aeOxfYsFwUlGjVLy78tGF4uBTICUDjDntMJhXgVEPkLI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=rtTCOqq+; 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="rtTCOqq+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A97981F000E9; Thu, 16 Jul 2026 13:59:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784210366; bh=cym4cv4HEAudk73lU1dzDe/nwdKMOww2V6xPokWphyQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=rtTCOqq+T+n3KPTbn5NTKubaxZLk8d1dtan387YXeNRcPHcdRxCS4cAIUek74lfEq b921g2fkYGVjvHnaYkY8MXewRNcODOC9xul/xE261KP4mOiq/dPai0Eh138gbgC4VW EW+UCKIBY+O7ytVxk36hEpwo8LJRfzQ01VcCrnGE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Mingyu Wang <25181214217@stu.xidian.edu.cn>, Thomas Zimmermann , Helge Deller , Sasha Levin Subject: [PATCH 6.18 020/480] fbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font() Date: Thu, 16 Jul 2026 15:26:07 +0200 Message-ID: <20260716133045.132734056@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260716133044.672218725@linuxfoundation.org> References: <20260716133044.672218725@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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mingyu Wang <25181214217@stu.xidian.edu.cn> [ Upstream commit 8fdc8c2057eea08d40ce2c8eed41ff9e451c65c2 ] 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 [ Adjust context ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/video/fbdev/core/fbcon.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2422,6 +2422,7 @@ static int fbcon_do_set_font(struct vc_d struct fbcon_display *p = &fb_display[vc->vc_num]; int resize, ret, old_userfont, old_width, old_height, old_charcount; u8 *old_data = vc->vc_font.data; + unsigned short old_hi_font_mask = vc->vc_hi_font_mask; resize = (w != vc->vc_font.width) || (h != vc->vc_font.height); vc->vc_font.data = (void *)(p->fontdata = data); @@ -2475,6 +2476,12 @@ err_out: 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); + return ret; }