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 DC5C937473A; Tue, 21 Jul 2026 21:56:45 +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=1784671008; cv=none; b=qeQeG5V7kecW8IrzAmcvz9DW2mFmihhdCaUtC0++dEZx96HMeG2YI8SAm84HcT/gNRh/aED9LNtmC9gKkrbvMooN84tkYmwltHZKKqFnlwlXNBcdgJyDalbh5ce8vMTT+qZj1csJFH3Ge1csnO+LwBYPhFi3kNc9VCxbqtnBsgk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784671008; c=relaxed/simple; bh=sV74SkNblvIaH3HwpXqxb2IDtTq2I9uO3iHDdpJGZfs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pDGMF1DQnhDbhc7V/R7RuzAfKt4I1aCABplPhdj3nbxX7vk+4DG/ZDmL8YqsslSmxhOpFc47reltsECTxjJ+8rdH3O0WaqcmAYE0HE96QZb1+RguQ6ZIoo2nsvKqoHM6+C2DbTCok0y10s6EBZ+Xz7a96c2IdEoDPhRErKcreeQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=TDtRpVnY; 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="TDtRpVnY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7549A1F00A3A; Tue, 21 Jul 2026 21:56:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784671005; bh=V3gwQkkHaN+kolzOYcywC+xvU5503SM9eRd+8JW2f9Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=TDtRpVnYB7j5R85pxrtSYnkaQ+V3lfISDZcRf9gRYhn5DVreiqPdZ4G9oYwMKlPje A5JmYvl6IAAAZ8ne47ZsoinpvIIocI4p8JlDyjWLQAcBIzTFGC+qzXxakYN1FdqfOE Zb4ou1cvEn/8C0EKgS1762ern4sIaRPITZN9YBSw= 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 5.15 040/843] fbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font() Date: Tue, 21 Jul 2026 17:14:35 +0200 Message-ID: <20260721152406.876885524@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152405.946368001@linuxfoundation.org> References: <20260721152405.946368001@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-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 @@ -2381,6 +2381,7 @@ 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); @@ -2434,6 +2435,12 @@ 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; }