From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793214247; b=rQUqy6nJ/NFImGQhJ0n1se9XSxmC5mJehuYoJQHI7SDCMphJgQ+7DGy1FPkKNjRXlsEX QfXwAjylgT3j307MxTkb0tTI9kx9cZa94RwFtxoFBa6y8VflGRr19QSWrQ0I1aaWs0bfc Lu0dBc4HXGKvYHJb5lxUzHEQ0MezO58QpACRgWcmU7eJ/bE1Y2PC9I33A54zrvNeMiBl4 Jqm1M17zXV8oYRZVOsEWnDi4HJrmoswinhIfIhDnD7LOtc30MlwS6tqrFvqNIiVwYbj8a zjh6f9uC3G+EUeXBELrLmEDcVRG8DlSSpWPYZm9nDC0sc2pLF256eZ7HxOfo1iiJuHg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793214247; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=4eNRnOpxULF7efB+btNx56pBuzayB25HPyh1I20TngQ=; b=F3KJSqyIeCgjislJt3pqMRe27Q94flNO7uO6OJ46UbuoLvCDrWdYL9kgmEjQ38xOqDXE AsedidZb8dAYUV4F+0pc1YcNg0jycBtQ9ASOlDEdaXWQ30/rUWG/ee2QYV8TLV6Miche6 gvxTp9Jht1HHgGrrdC4gJk7xTKHIQq2vpEVyOYmvC28Vz/Vw0aN79krbjqKvGgqpUGbSD 5W9RCBbfJ89oe0X5k6rhEboG2k0eudRPK7nzEI0jpvRo62wfKG/cc+kA1/QX1wpgQphh7 rJI4z6HzZvS6jGAsQezwqTQxebNU57j91F2aOEYeBxNNvJk5+fFOOXztzF1f76ARipQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=FfRv7qXs; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C183960A3825; Wed, 28 Oct 2026 19:04:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=FfRv7qXs Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1F10D1F031E0; Wed, 28 Oct 2026 19:04:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793214246; bh=4eNRnOpxULF7efB+btNx56pBuzayB25HPyh1I20TngQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=FfRv7qXsW7+saOdmv+ygT/xCyf4Eftf7LtK52Vnzbyw9D/7vnnoHD8NHWe0Zv/BJ9 6PMlKB+ds+kpeOtzIn8kiwAJpbFAJrbk4YcNNoLmSSEijYx9uDXjapHR+H/5k4ofZJ xbTQ7qSeowGqMfC9NvuSSJQgbNuXxKSj8QbMNP3M= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+33841dc6aa3e1d86b78a@syzkaller.appspotmail.com, Murad Masimov , "David S. Miller" , Sasha Levin Subject: [PATCH 6.1 0764/1887] ax25: Remove broken autobind Date: Wed, 28 Oct 2026 17:47:40 +0100 Message-ID: <20261028170516.827632563@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028170459.200466217@linuxfoundation.org> References: <20261028170459.200466217@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Murad Masimov [ Upstream commit 2f6efbabceb6b2914ee9bafb86d9a51feae9cce8 ] Binding AX25 socket by using the autobind feature leads to memory leaks in ax25_connect() and also refcount leaks in ax25_release(). Memory leak was detected with kmemleak: ================================================================ unreferenced object 0xffff8880253cd680 (size 96): backtrace: __kmalloc_node_track_caller_noprof (./include/linux/kmemleak.h:43) kmemdup_noprof (mm/util.c:136) ax25_rt_autobind (net/ax25/ax25_route.c:428) ax25_connect (net/ax25/af_ax25.c:1282) __sys_connect_file (net/socket.c:2045) __sys_connect (net/socket.c:2064) __x64_sys_connect (net/socket.c:2067) do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) ================================================================ When socket is bound, refcounts must be incremented the way it is done in ax25_bind() and ax25_setsockopt() (SO_BINDTODEVICE). In case of autobind, the refcounts are not incremented. This bug leads to the following issue reported by Syzkaller: ================================================================ ax25_connect(): syz-executor318 uses autobind, please contact jreuter@yaina.de ------------[ cut here ]------------ refcount_t: decrement hit 0; leaking memory. WARNING: CPU: 0 PID: 5317 at lib/refcount.c:31 refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:31 Modules linked in: CPU: 0 UID: 0 PID: 5317 Comm: syz-executor318 Not tainted 6.14.0-rc4-syzkaller-00278-gece144f151ac #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:31 ... Call Trace: __refcount_dec include/linux/refcount.h:336 [inline] refcount_dec include/linux/refcount.h:351 [inline] ref_tracker_free+0x6af/0x7e0 lib/ref_tracker.c:236 netdev_tracker_free include/linux/netdevice.h:4302 [inline] netdev_put include/linux/netdevice.h:4319 [inline] ax25_release+0x368/0x960 net/ax25/af_ax25.c:1080 __sock_release net/socket.c:647 [inline] sock_close+0xbc/0x240 net/socket.c:1398 __fput+0x3e9/0x9f0 fs/file_table.c:464 __do_sys_close fs/open.c:1580 [inline] __se_sys_close fs/open.c:1565 [inline] __x64_sys_close+0x7f/0x110 fs/open.c:1565 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f ... ================================================================ Considering the issues above and the comments left in the code that say: "check if we can remove this feature. It is broken."; "autobinding in this may or may not work"; - it is better to completely remove this feature than to fix it because it is broken and leads to various kinds of memory bugs. Now calling connect() without first binding socket will result in an error (-EINVAL). Userspace software that relies on the autobind feature might get broken. However, this feature does not seem widely used with this specific driver as it was not reliable at any point of time, and it is already broken anyway. E.g. ax25-tools and ax25-apps packages for popular distributions do not use the autobind feature for AF_AX25. Found by Linux Verification Center (linuxtesting.org) with Syzkaller. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot+33841dc6aa3e1d86b78a@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=33841dc6aa3e1d86b78a Signed-off-by: Murad Masimov Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- include/net/ax25.h | 1 - net/ax25/af_ax25.c | 30 ++++++------------ net/ax25/ax25_route.c | 74 ------------------------------------------- 3 files changed, 10 insertions(+), 95 deletions(-) diff --git a/include/net/ax25.h b/include/net/ax25.h index e9465aa07a4e7..6b29f3a30cfa0 100644 --- a/include/net/ax25.h +++ b/include/net/ax25.h @@ -419,7 +419,6 @@ void ax25_rt_device_down(struct net_device *); int ax25_rt_ioctl(unsigned int, void __user *); extern const struct seq_operations ax25_rt_seqops; ax25_route *ax25_get_route(ax25_address *addr, struct net_device *dev); -int ax25_rt_autobind(ax25_cb *, ax25_address *); struct sk_buff *ax25_rt_build_path(struct sk_buff *, ax25_address *, ax25_address *, ax25_digi *); void ax25_rt_free(void); diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index 862e03493b7ed..64b81a693e25e 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -1270,28 +1270,18 @@ static int __must_check ax25_connect(struct socket *sock, } } - /* - * Must bind first - autobinding in this may or may not work. If - * the socket is already bound, check to see if the device has - * been filled in, error if it hasn't. - */ + /* Must bind first - autobinding does not work. */ if (sock_flag(sk, SOCK_ZAPPED)) { - /* check if we can remove this feature. It is broken. */ - printk(KERN_WARNING "ax25_connect(): %s uses autobind, please contact jreuter@yaina.de\n", - current->comm); - if ((err = ax25_rt_autobind(ax25, &fsa->fsa_ax25.sax25_call)) < 0) { - kfree(digi); - goto out_release; - } + kfree(digi); + err = -EINVAL; + goto out_release; + } - ax25_fillin_cb(ax25, ax25->ax25_dev); - ax25_cb_add(ax25); - } else { - if (ax25->ax25_dev == NULL) { - kfree(digi); - err = -EHOSTUNREACH; - goto out_release; - } + /* Check to see if the device has been filled in, error if it hasn't. */ + if (ax25->ax25_dev == NULL) { + kfree(digi); + err = -EHOSTUNREACH; + goto out_release; } if (sk->sk_type == SOCK_SEQPACKET && diff --git a/net/ax25/ax25_route.c b/net/ax25/ax25_route.c index 69de75db0c9c2..10577434f40bf 100644 --- a/net/ax25/ax25_route.c +++ b/net/ax25/ax25_route.c @@ -373,80 +373,6 @@ ax25_route *ax25_get_route(ax25_address *addr, struct net_device *dev) return ax25_rt; } -/* - * Adjust path: If you specify a default route and want to connect - * a target on the digipeater path but w/o having a special route - * set before, the path has to be truncated from your target on. - */ -static inline void ax25_adjust_path(ax25_address *addr, ax25_digi *digipeat) -{ - int k; - - for (k = 0; k < digipeat->ndigi; k++) { - if (ax25cmp(addr, &digipeat->calls[k]) == 0) - break; - } - - digipeat->ndigi = k; -} - - -/* - * Find which interface to use. - */ -int ax25_rt_autobind(ax25_cb *ax25, ax25_address *addr) -{ - ax25_uid_assoc *user; - ax25_route *ax25_rt; - int err = 0; - - ax25_route_lock_use(); - ax25_rt = ax25_get_route(addr, NULL); - if (!ax25_rt) { - ax25_route_lock_unuse(); - return -EHOSTUNREACH; - } - rcu_read_lock(); - if ((ax25->ax25_dev = ax25_dev_ax25dev(ax25_rt->dev)) == NULL) { - err = -EHOSTUNREACH; - goto put; - } - - user = ax25_findbyuid(current_euid()); - if (user) { - ax25->source_addr = user->call; - ax25_uid_put(user); - } else { - if (ax25_uid_policy && !capable(CAP_NET_BIND_SERVICE)) { - err = -EPERM; - goto put; - } - ax25->source_addr = *(ax25_address *)ax25->ax25_dev->dev->dev_addr; - } - - if (ax25_rt->digipeat != NULL) { - ax25->digipeat = kmemdup(ax25_rt->digipeat, sizeof(ax25_digi), - GFP_ATOMIC); - if (ax25->digipeat == NULL) { - err = -ENOMEM; - goto put; - } - ax25_adjust_path(addr, ax25->digipeat); - } - - if (ax25->sk != NULL) { - local_bh_disable(); - bh_lock_sock(ax25->sk); - sock_reset_flag(ax25->sk, SOCK_ZAPPED); - bh_unlock_sock(ax25->sk); - local_bh_enable(); - } - -put: - rcu_read_unlock(); - ax25_route_lock_unuse(); - return err; -} struct sk_buff *ax25_rt_build_path(struct sk_buff *skb, ax25_address *src, ax25_address *dest, ax25_digi *digi) -- 2.53.0