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 16B603672BA; Tue, 21 Jul 2026 17:41:16 +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=1784655677; cv=none; b=j80bGUR2MQbXrlIB5780FkcO2rqByplsuZ9Skfc3NJT0BC1oYey36D/lIDJ/JNnC+UCBmqjRp/GKNgq8bNBollhQF0Cp5uLqxvXWT7FLiB3c4wOJQZUDArs01PywN5xqPnwKRV211IxahVZccWG9M3CvwbMNeaottrNUGzmmSPA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784655677; c=relaxed/simple; bh=d+b+aQP3UZue+sJOw1oX59/N3Kx2KJ2jzOW0RYN8KC0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=qkHohC2WQIHBYvDGvagxFfvRV5bbcMMfG1p8xuaS8m+VzSz26/8Z+UemWktGN/THNFlYE4NU5WPHDUgWe1dYBMfPYhvi+PT7zLAh/JgH0NLBdeMgDyUtsg4IFF5GrvNQ5iVfBzHGDrGsCWD8Ag9LVvjgOjCrQwhL6vIWf1Mot2c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=1SPnCt1S; 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="1SPnCt1S" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 385071F000E9; Tue, 21 Jul 2026 17:41:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784655675; bh=zLYDj1lVi//kR25S1Ma4SRYAYyitkLvlnpQl6S/8gHw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=1SPnCt1Sim15RbrHV6uyIgAr9eyDOgkFCQZbxR7FHvRinKSPvIQlvtMrJwhnz5CyF lJV8c/fqJBcl9h4pZTN1yaS7NSEfN4XjFJxEi9xwSc049VBKm9eyrNtPpK9/lkJrEb Wg6z9SEWJdgF8VAECuNlAV8/mg+qPOt11M8+niLU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+42525d636f430fd5d983@syzkaller.appspotmail.com, Ian Bridges , Helge Deller Subject: [PATCH 6.18 0055/1611] fbcon: fix NULL pointer dereference for a console without vc_data Date: Tue, 21 Jul 2026 17:02:51 +0200 Message-ID: <20260721152516.063158007@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152514.750365251@linuxfoundation.org> References: <20260721152514.750365251@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: Ian Bridges commit 5fae9a928482d4845bca169a3a098789203a1ca4 upstream. fbcon_new_modelist() runs when a framebuffer's modelist changes. For each console mapped to it with fb_display[i].mode set, it reads vc_cons[i].d and passes the vc_num to fbcon_set_disp(). This assumes a console with a mode set has a vc_data, but it can be NULL. fbcon_set_disp() sets fb_display[i].mode before it checks vc_data, and fbcon_deinit() leaves the mode set after the vc_data is freed. fbcon_new_modelist() then dereferences the NULL vc_data. Keep fb_display[i].mode set only while the console has a vc_data. Check vc_data before setting the mode in fbcon_set_disp(), and clear the mode in fbcon_deinit(). The existing mode check in fbcon_new_modelist() then skips such consoles. Reported-by: syzbot+42525d636f430fd5d983@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=42525d636f430fd5d983 Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Ian Bridges Signed-off-by: Helge Deller Signed-off-by: Greg Kroah-Hartman --- drivers/video/fbdev/core/fbcon.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -1205,6 +1205,7 @@ static void fbcon_deinit(struct vc_data int idx; fbcon_free_font(p); + p->mode = NULL; idx = con2fb_map[vc->vc_num]; if (idx == -1) @@ -1375,14 +1376,14 @@ static void fbcon_set_disp(struct fb_inf p = &fb_display[unit]; - if (var_to_display(p, var, info)) - return; - vc = vc_cons[unit].d; if (!vc) return; + if (var_to_display(p, var, info)) + return; + default_mode = vc->vc_display_fg; svc = *default_mode; t = &fb_display[svc->vc_num];