From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 6ED631B6CE9 for ; Mon, 8 Dec 2025 00:49:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765154942; cv=none; b=kaDxowb4XiM929p4EFEax1itPqYdzxjxJ498uW9tXc7nMRWj+PijVYZbvCdGIh8VPRUk1BAm51JkVlo7ZQ7RulR+gDhRB1CqqBwGy0K9ilZ8JbsOPdFTIQC/z9U96FQ3ZVWCnGSNB0sD1w13NqvVFbzdm9sJFaIZYEkp1MpunuE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765154942; c=relaxed/simple; bh=XUy0v5DrjO2/wIWqEJ7mjilp8oqWti2nWFJVhrjzt9Q=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=pG4D6ZMeaI2lcSgyTX/EhIryJ5iraQ2hKIXlgz9A+ONdSeF+DqpFnbuNYYAALjCklcFVFXHUbY9lVkU2KTCh76ioXD7XlhiatVjVdZ1cEzTSRl4ZhqpUTwdLIwlcj6Y8Hi3YU7uHQ/m9UX+FUITE7wbN0JS5htsA6nn8w+9yk0E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=wdVnpRuO; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="wdVnpRuO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 06718C4CEFB; Mon, 8 Dec 2025 00:49:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1765154942; bh=XUy0v5DrjO2/wIWqEJ7mjilp8oqWti2nWFJVhrjzt9Q=; h=From:To:Cc:Subject:Date:Reply-To:From; b=wdVnpRuOpjFR4S1tChhKyEywOLWTVhI9O7kfNyC/ISjN+uN14eQW86dMim9EpTLPW ssU9dKPaJ+8JrYzkt8Z+ED9/uKf2b1/zC8WQm8xZGSOsWaqDgeUOtY5TrH8Rj0p/38 JolpMPIDLNzrzgBRgdT3oXfDQQ99+Jo66oHmnz9k= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2025-40323: fbcon: Set fb_display[i]->mode to NULL when the mode is released Date: Mon, 8 Dec 2025 09:47:47 +0900 Message-ID: <2025120824-CVE-2025-40323-047f@gregkh> X-Mailer: git-send-email 2.52.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3603; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=kGIeM5yNbtYF+fidSUzssLLkS/rIg2aZZk28x7nhGUQ=; b=owGbwMvMwCRo6H6F97bub03G02pJDJlmCjLNEyv2Vi9/MGn145R/NQl/4/fV7P6uWCu4M4/pi 9OV3ijujlgWBkEmBlkxRZYv23iO7q84pOhlaHsaZg4rE8gQBi5OAZjIunkM8/TWZTVc3KX+93Au l0VBbb3vw87kqQzz83z/bzzG3LBJSMmMlV+nkGfbMa4GAA== X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: fbcon: Set fb_display[i]->mode to NULL when the mode is released Recently, we discovered the following issue through syzkaller: BUG: KASAN: slab-use-after-free in fb_mode_is_equal+0x285/0x2f0 Read of size 4 at addr ff11000001b3c69c by task syz.xxx ... Call Trace: dump_stack_lvl+0xab/0xe0 print_address_description.constprop.0+0x2c/0x390 print_report+0xb9/0x280 kasan_report+0xb8/0xf0 fb_mode_is_equal+0x285/0x2f0 fbcon_mode_deleted+0x129/0x180 fb_set_var+0xe7f/0x11d0 do_fb_ioctl+0x6a0/0x750 fb_ioctl+0xe0/0x140 __x64_sys_ioctl+0x193/0x210 do_syscall_64+0x5f/0x9c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e Based on experimentation and analysis, during framebuffer unregistration, only the memory of fb_info->modelist is freed, without setting the corresponding fb_display[i]->mode to NULL for the freed modes. This leads to UAF issues during subsequent accesses. Here's an example of reproduction steps: 1. With /dev/fb0 already registered in the system, load a kernel module to register a new device /dev/fb1; 2. Set fb1's mode to the global fb_display[] array (via FBIOPUT_CON2FBMAP); 3. Switch console from fb to VGA (to allow normal rmmod of the ko); 4. Unload the kernel module, at this point fb1's modelist is freed, leaving a wild pointer in fb_display[]; 5. Trigger the bug via system calls through fb0 attempting to delete a mode from fb0. Add a check in do_unregister_framebuffer(): if the mode to be freed exists in fb_display[], set the corresponding mode pointer to NULL. The Linux kernel CVE team has assigned CVE-2025-40323 to this issue. Affected and fixed versions =========================== Fixed in 6.1.159 with commit 4ac18f0e6a6d599ca751c4cd98e522afc8e3d4eb Fixed in 6.6.117 with commit 468f78276a37f4c6499385a4ce28f4f57be6655d Fixed in 6.12.58 with commit c079d42f70109512eee49123a843be91d8fa133f Fixed in 6.17.8 with commit de89d19f4f30d9a8de87b9d08c1bd35cb70576d8 Fixed in 6.18 with commit a1f3058930745d2b938b6b4f5bd9630dc74b26b7 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2025-40323 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: drivers/video/fbdev/core/fbcon.c drivers/video/fbdev/core/fbmem.c include/linux/fbcon.h Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/4ac18f0e6a6d599ca751c4cd98e522afc8e3d4eb https://git.kernel.org/stable/c/468f78276a37f4c6499385a4ce28f4f57be6655d https://git.kernel.org/stable/c/c079d42f70109512eee49123a843be91d8fa133f https://git.kernel.org/stable/c/de89d19f4f30d9a8de87b9d08c1bd35cb70576d8 https://git.kernel.org/stable/c/a1f3058930745d2b938b6b4f5bd9630dc74b26b7