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 28A9137FF71 for ; Sun, 5 Jul 2026 14:00:58 +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=1783260059; cv=none; b=hZ8w8mAtpob5QWLPhe0p3xu7hFijlgmQ/jmKjFclYsB7HfYl3ZbK644dBuPpYIewnRxE7MetZYggrpM/DZL02T1qLoCn0BD1IbifwBDbf1B/06aHjl3k5gv6eNuqllZAxGfaFsA/LEmATWy+PzhvLhnFudsUc4/b84EVhtXiADY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783260059; c=relaxed/simple; bh=A/zMK3GIRqtmjqhN1YBDJKFNTO1FCWMfWMMiwSE0pH4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=e3YojrUo5jkmyfpCFXpBUrEwGT2DC17nCHBR9EnogcYGRd9KXgWMmSfIbFh912bo5xtvDx5AHc6DAeN6jPX0iLx8ZuYZ1sWdFQf2vNgQ0iZTpYv34Cllh1NMkaWWWjw48opB+0iSRl2Z2sPJBx+BafcpwQjO+OXBiQ8/59iQQEY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=U1kNjJBa; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="U1kNjJBa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5DB371F00A3D; Sun, 5 Jul 2026 14:00:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783260057; bh=AF71D8Quu048x3csOv74CmMGr4qcAK5RE/A/gtxqOJs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=U1kNjJBaYeM9aNVnLPYSy457MQG2uW3w6tZq19iNDVOB2SRHn/poAsMbCJzg5rNP7 Dx1TqV6fzeO2hPJA1TYJ3ZPwQJOoaaZwqmrMRHzwUQ4tuXK3FkE2BxH40nkH9avQBA v6FwzqR577yNQ4H/QJWaQ2g07qkxPbaBHb6zOMJU49nD6KJKeGAiTgKRCrmIDYmbI6 UmiCFeZpr8lPdE3WMSzWaj9+afqq62ChqvIc2HqDgYnabJRYsDL2gI9CFaG5p5NHi1 1zGPvKwpbvfNX29aUyQ7OWtpZXU5ngzIeYoUyfjlFtG4/li8e+0J4qiS8hE65wPyGs ZZHCXLjD/GZqw== From: Sasha Levin To: stable@vger.kernel.org Cc: Mingyu Wang <25181214217@stu.xidian.edu.cn>, Thomas Zimmermann , Helge Deller , Sasha Levin Subject: [PATCH 6.1.y] fbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font() Date: Sun, 5 Jul 2026 10:00:55 -0400 Message-ID: <20260705140055.1744629-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026070230-shaping-renewably-c158@gregkh> References: <2026070230-shaping-renewably-c158@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- drivers/video/fbdev/core/fbcon.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 015baff0192908..00c2841c23068f 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2415,6 +2415,7 @@ static int fbcon_do_set_font(struct vc_data *vc, int w, int h, int charcount, 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); @@ -2468,6 +2469,12 @@ 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); + return ret; } -- 2.53.0