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 51CDB3E3DB8 for ; Wed, 27 May 2026 12:20:48 +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=1779884449; cv=none; b=lZILrwySH7E3hLqjf030ZmImnfs/PdLxTen1Ow04lepKm1nPyBZW7D/ep8PyFLcLYUZmr3FZvY+e6lLO5dcq0xXp7VzFWDP8v/Fg7r9HJgjEPlDUDk3xT11/7RpblME2pfJluQuHenIXvtZPHcRsTjp5/DaXDVABthypaBvX83I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779884449; c=relaxed/simple; bh=Eh76D1A1GYujWphVJig4eo5eE+Z/2U+k5abkhY6Xsr0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=s+Fsef1eW0wJDYqhMAABfxSVqAAytKPbL8rb+O4ZHSo5Vl3b7mZkA4VOEMpsamrcncFeUk7eAKwAiXz+54XeuJ0BrDYybT4UVHGLgqS3b2eQI9hJNRKggmS8dQT6hi9wLqj2BZhxaL/Z84swW3pXwCgzVxM/64gsCqy3XEsXYe8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=HGAVjuVu; 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="HGAVjuVu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 881DB1F000E9; Wed, 27 May 2026 12:20:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1779884448; bh=VAccDuhfatX+Iyhg2vocCp5FUTa8IvaRa0KUPU4ulQk=; h=From:To:Cc:Subject:Date:Reply-To; b=HGAVjuVuhRsuIdn75CC50AW9zmgDvZtdkvNnDNUPd/AaeFcm7KVdXt5taxr+L2wa7 k2BVmiE174xkw2NKHdlm9KwlxDYtIez5O4pPJLCxHCmDcCffOLoPb3V6GF+LYhrJtB C23YbWYHd/2LaDm+E9ord7r7gl1ghSeuHFydrjcQ= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-45866: serial: caif: fix use-after-free in caif_serial ldisc_close() Date: Wed, 27 May 2026 14:18:28 +0200 Message-ID: <2026052712-CVE-2026-45866-268a@gregkh> X-Mailer: git-send-email 2.54.0 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=6921; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=bqyZ7PuBL53zN8hkHoVO+84M6QWu4azEEF8brky+KlU=; b=owGbwMvMwCRo6H6F97bub03G02pJDFliD1le+t5q4Ap+w/LH9s21JK8nvVcNa3aslbmeLZ2hf Dwh/ENjRywLgyATg6yYIsuXbTxH91ccUvQytD0NM4eVCWQIAxenAExkjjTDgrXR5rae5fs3BN1i kvqt67Xp5F/lRQwLLiU5xbd8+uIQtkfEUJ059Ye3/r0yAA== 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: serial: caif: fix use-after-free in caif_serial ldisc_close() There is a use-after-free bug in caif_serial where handle_tx() may access ser->tty after the tty has been freed. The race condition occurs between ldisc_close() and packet transmission: CPU 0 (close) CPU 1 (xmit) ------------- ------------ ldisc_close() tty_kref_put(ser->tty) [tty may be freed here] <-- race window --> caif_xmit() handle_tx() tty = ser->tty // dangling ptr tty->ops->write() // UAF! schedule_work() ser_release() unregister_netdevice() The root cause is that tty_kref_put() is called in ldisc_close() while the network device is still active and can receive packets. Since ser and tty have a 1:1 binding relationship with consistent lifecycles (ser is allocated in ldisc_open and freed in ser_release via unregister_netdevice, and each ser binds exactly one tty), we can safely defer the tty reference release to ser_release() where the network device is unregistered. Fix this by moving tty_kref_put() from ldisc_close() to ser_release(), after unregister_netdevice(). This ensures the tty reference is held as long as the network device exists, preventing the UAF. Note: We save ser->tty before unregister_netdevice() because ser is embedded in netdev's private data and will be freed along with netdev (needs_free_netdev = true). How to reproduce: Add mdelay(500) at the beginning of ldisc_close() to widen the race window, then run the reproducer program [1]. Note: There is a separate deadloop issue in handle_tx() when using PORT_UNKNOWN serial ports (e.g., /dev/ttyS3 in QEMU without proper serial backend). This deadloop exists even without this patch, and is likely caused by inconsistency between uart_write_room() and uart_write() in serial core. It has been addressed in a separate patch [2]. KASAN report: ================================================================== BUG: KASAN: slab-use-after-free in handle_tx+0x5d1/0x620 Read of size 1 at addr ffff8881131e1490 by task caif_uaf_trigge/9929 Call Trace: dump_stack_lvl+0x10e/0x1f0 print_report+0xd0/0x630 kasan_report+0xe4/0x120 handle_tx+0x5d1/0x620 dev_hard_start_xmit+0x9d/0x6c0 __dev_queue_xmit+0x6e2/0x4410 packet_xmit+0x243/0x360 packet_sendmsg+0x26cf/0x5500 __sys_sendto+0x4a3/0x520 __x64_sys_sendto+0xe0/0x1c0 do_syscall_64+0xc9/0xf80 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f615df2c0d7 Allocated by task 9930: Freed by task 64: Last potentially related work creation: The buggy address belongs to the object at ffff8881131e1000 which belongs to the cache kmalloc-cg-2k of size 2048 The buggy address is located 1168 bytes inside of freed 2048-byte region [ffff8881131e1000, ffff8881131e1800) The buggy address belongs to the physical page: page_owner tracks the page as allocated page last free pid 9778 tgid 9778 stack trace: Memory state around the buggy address: ffff8881131e1380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8881131e1400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8881131e1480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8881131e1500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8881131e1580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== [1]: https://gist.github.com/mrpre/f683f244544f7b11e7fa87df9e6c2eeb [2]: https://lore.kernel.org/linux-serial/20260204074327.226165-1-jiayuan.chen@linux.dev/T/#u The Linux kernel CVE team has assigned CVE-2026-45866 to this issue. Affected and fixed versions =========================== Issue introduced in 3.11 with commit 56e0ef527b184b3de2d7f88c6190812b2b2ac6bf and fixed in 5.10.252 with commit 5e266ba8d330d3b8e5bc198f238cd8901826cfa1 Issue introduced in 3.11 with commit 56e0ef527b184b3de2d7f88c6190812b2b2ac6bf and fixed in 5.15.202 with commit d3c75db4e0460641dbcd274b40867e252d801da1 Issue introduced in 3.11 with commit 56e0ef527b184b3de2d7f88c6190812b2b2ac6bf and fixed in 6.1.165 with commit 4e63d6f68544ae5269ac9735ae5b69b59b5b8725 Issue introduced in 3.11 with commit 56e0ef527b184b3de2d7f88c6190812b2b2ac6bf and fixed in 6.6.128 with commit 331e2b7051635780edea248dd08ae2026c126f4a Issue introduced in 3.11 with commit 56e0ef527b184b3de2d7f88c6190812b2b2ac6bf and fixed in 6.12.75 with commit 52731ef4438155cea782fac74e547a327ab9e7c5 Issue introduced in 3.11 with commit 56e0ef527b184b3de2d7f88c6190812b2b2ac6bf and fixed in 6.18.14 with commit c8c197aaa56b25a2d54f3aa07e27e228d6c08546 Issue introduced in 3.11 with commit 56e0ef527b184b3de2d7f88c6190812b2b2ac6bf and fixed in 6.19.4 with commit 40962f2bf8cdba63af23aec95ad3f49b689e58e2 Issue introduced in 3.11 with commit 56e0ef527b184b3de2d7f88c6190812b2b2ac6bf and fixed in 7.0 with commit 308e7e4d0a846359685f40aade023aee7b27284c 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-2026-45866 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/net/caif/caif_serial.c 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/5e266ba8d330d3b8e5bc198f238cd8901826cfa1 https://git.kernel.org/stable/c/d3c75db4e0460641dbcd274b40867e252d801da1 https://git.kernel.org/stable/c/4e63d6f68544ae5269ac9735ae5b69b59b5b8725 https://git.kernel.org/stable/c/331e2b7051635780edea248dd08ae2026c126f4a https://git.kernel.org/stable/c/52731ef4438155cea782fac74e547a327ab9e7c5 https://git.kernel.org/stable/c/c8c197aaa56b25a2d54f3aa07e27e228d6c08546 https://git.kernel.org/stable/c/40962f2bf8cdba63af23aec95ad3f49b689e58e2 https://git.kernel.org/stable/c/308e7e4d0a846359685f40aade023aee7b27284c