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 C6B21376490 for ; Sun, 5 Jul 2026 14:25:02 +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=1783261504; cv=none; b=hXckgL3tZqmuZYxo7lrZh/J5y/vMMmunsfzQ7G0VmmCXJGBmZfiHCafFWK3XPcHPesdCQpjT+Atw4GyrnP0tU7O2jF2hTfpyRh7wBVXBx5mYqtMsN2c9X/KRsN0NCurVeE95W+soAAXJBHbuVw4Gfr6RoHbbPQfEvqfmD813e/Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783261504; c=relaxed/simple; bh=9+Z3LFJ1TUoyOzawIkHkpoTBgkb/cLpvH0/Nfrm+Y4w=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=oAZi+PPdMe9S2v+geUByrV75AERhNHi9NQl4vs9qD+IE5GcsRx/sOZhmykIB/+TpuXZnlhe2gkcFAYpNCwkjw963k9kjYwDp2Ro1CbNXEP6qbxWqllY4t0J6JNKHIewweng6crw65x6ielAIQmYxqLyrp4EC/jyDjhhQuiBZDAg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PcuNUD8C; 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="PcuNUD8C" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CE4691F000E9; Sun, 5 Jul 2026 14:25:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783261502; bh=cOkS407vKO4+ufm49cPCAOV2jl9ZYDiOs917R0Xdec0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=PcuNUD8C+ykg5D8D2l6eAM6h+sk0A5bPRZeVDl/ue7J1/LnqfPzeI+RMyVrLY71TC +KRxiaVRWnvCnoBiMTn/AFDRzDbE/XctXciemSXCrQvyeQ929zbGoViuHTsqFWCm31 efpufMKeWWmBnbMuXay8iXeRhaJ62NlJ9zP89O32V0gpDw5NL8SXKukJ+hODo6hPtf RNChR6ruwB5FUscTfjy7k4EPWNmOm8eQu2m9gGZKmrhXEK7mvDOksj12REq/FLH2/s VvdgWR1TvaczAdGhSCEHyg/SJEs0gUiMAXRBEtmvFm0v+iyycU1QuQupoJwODA+jfO kvRSfECZcFNug== From: Sasha Levin To: stable@vger.kernel.org Cc: Mingyu Wang <25181214217@stu.xidian.edu.cn>, Thomas Zimmermann , Helge Deller , Sasha Levin Subject: [PATCH 5.10.y] fbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font() Date: Sun, 5 Jul 2026 10:24:59 -0400 Message-ID: <20260705142459.1798975-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026070231-lash-wick-98ec@gregkh> References: <2026070231-lash-wick-98ec@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 00cd29a3bddc1b..b72d7bf448793a 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2426,6 +2426,7 @@ 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); @@ -2479,6 +2480,12 @@ 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