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 F08C33793AA for ; Sun, 5 Jul 2026 13:48:04 +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=1783259286; cv=none; b=jPDWrJlyZf+LnMs8tDqbrwnNGlNdjmZDGSfzRSLpX8SyhyATxeRGGdea6w+cRVtFHTSWFepQ4bRakez+Nw6uS2dAL/LQ15wLTFZoXXN0wZRgc7qlH6BZRCQ2LQRpC4BFvIj0j1se7R/r9AaqeFOiON89Hn+oiChSXVC5ErKC80s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783259286; c=relaxed/simple; bh=Kd34TJg+x6ai0CKYv+574DED0njug/7Roe3azyTiav4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Bo+a4ZJ5lYfSvoQFtUg7HVS0fBb9H1APzgFDmqXDPVfYtzoWcTT9d1giuPMgI1QOkO/xNR+Cj8Zifb6gJfpdEst5uU/OFo96ksyY4UD4W0ClgLFvUr3AMXgxxa+1DP54Uww3NdXbEqAzT4V2nWOprap+YdpcFPxSLO90E/zjEw4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lCzox0P8; 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="lCzox0P8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 385EF1F00A3A; Sun, 5 Jul 2026 13:48:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783259284; bh=cs8HLkI+yCJ5Id9PhD8I3qGcRWnqSVYn1WKA2Ps1Db4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=lCzox0P8+Hmx+Zq9hI1j3iImdSU4JYNLnvFBjSeZ08LrW7mmtEzf7cAktvXXQDww2 76nDvhiGRjHU6X8FQVCeGInLE0nwyHkjbN9tGQC1fESPB569uOfRtqVI9x2DBSzYpp GNvtsi0Mnbyc7y+9GpDH5QJo+93TrnlnMgPD4ZP1VT4GSCcvJuTrx54772l2th1rqE tlS8WklXYxZf4pxsROr0yMU5FtE/TnyoYelY79907rdobWPMHOEK1p57i8AGJQtfAw E9Vd2aMnkT/ZpdHz5A1QkY2wBgmQ+jIP2s05ZdHxnf1Vm/chW+hwft9Tgp/tlWWzo6 8gu1PcL+4WwPQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Mingyu Wang <25181214217@stu.xidian.edu.cn>, Thomas Zimmermann , Helge Deller , Sasha Levin Subject: [PATCH 6.6.y] fbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font() Date: Sun, 5 Jul 2026 09:48:02 -0400 Message-ID: <20260705134802.1722907-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026070230-citrus-unboxed-57bc@gregkh> References: <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-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 d1ac4e45eea68e..a12d699dcb83b2 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2418,6 +2418,7 @@ 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); @@ -2471,6 +2472,12 @@ 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