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[2620:137:e000::1:20]) by mx.google.com with ESMTP id b17-20020a056402279100b00462a20f860bsi1401207ede.539.2022.10.27.05.49.15; Thu, 27 Oct 2022 05:49:42 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=huawei.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235743AbiJ0Mqb (ORCPT + 99 others); Thu, 27 Oct 2022 08:46:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33404 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235020AbiJ0Mqa (ORCPT ); Thu, 27 Oct 2022 08:46:30 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C364561B1F; Thu, 27 Oct 2022 05:46:28 -0700 (PDT) Received: from kwepemi500024.china.huawei.com (unknown [172.30.72.57]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4Mylfg6cXWz15MCN; Thu, 27 Oct 2022 20:41:31 +0800 (CST) Received: from huawei.com (10.175.103.91) by kwepemi500024.china.huawei.com (7.221.188.100) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Thu, 27 Oct 2022 20:46:25 +0800 From: Zeng Heng To: , , , , CC: , , , Subject: [PATCH v4] cifs: fix use-after-free caused by invalid pointer `hostname` Date: Thu, 27 Oct 2022 20:45:28 +0800 Message-ID: <20221027124528.2487025-1-zengheng4@huawei.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-Originating-IP: [10.175.103.91] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To kwepemi500024.china.huawei.com (7.221.188.100) X-CFilter-Loop: Reflected X-Spam-Status: No, score=-3.2 required=5.0 tests=BAYES_00,HEXHASH_WORD, RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1747845101611692053?= X-GMAIL-MSGID: =?utf-8?q?1747845101611692053?= `hostname` needs to be set as null-pointer after free in `cifs_put_tcp_session` function, or when `cifsd` thread attempts to resolve hostname and reconnect the host, the thread would deref the invalid pointer. Here is one of practical backtrace examples as reference: Task 477 --------------------------- do_mount path_mount do_new_mount vfs_get_tree smb3_get_tree smb3_get_tree_common cifs_smb3_do_mount cifs_mount mount_put_conns cifs_put_tcp_session --> kfree(server->hostname) cifsd --------------------------- kthread cifs_demultiplex_thread cifs_reconnect reconn_set_ipaddr_from_hostname --> if (!server->hostname) --> if (server->hostname[0] == '\0') // !! UAF fault here CIFS: VFS: cifs_mount failed w/return code = -112 mount error(112): Host is down BUG: KASAN: use-after-free in reconn_set_ipaddr_from_hostname+0x2ba/0x310 Read of size 1 at addr ffff888108f35380 by task cifsd/480 CPU: 2 PID: 480 Comm: cifsd Not tainted 6.1.0-rc2-00106-gf705792f89dd-dirty #25 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 Call Trace: dump_stack_lvl+0x68/0x85 print_report+0x16c/0x4a3 kasan_report+0x95/0x190 reconn_set_ipaddr_from_hostname+0x2ba/0x310 __cifs_reconnect.part.0+0x241/0x800 cifs_reconnect+0x65f/0xb60 cifs_demultiplex_thread+0x1570/0x2570 kthread+0x2c5/0x380 ret_from_fork+0x22/0x30 Allocated by task 477: kasan_save_stack+0x1e/0x40 kasan_set_track+0x21/0x30 __kasan_kmalloc+0x7e/0x90 __kmalloc_node_track_caller+0x52/0x1b0 kstrdup+0x3b/0x70 cifs_get_tcp_session+0xbc/0x19b0 mount_get_conns+0xa9/0x10c0 cifs_mount+0xdf/0x1970 cifs_smb3_do_mount+0x295/0x1660 smb3_get_tree+0x352/0x5e0 vfs_get_tree+0x8e/0x2e0 path_mount+0xf8c/0x1990 do_mount+0xee/0x110 __x64_sys_mount+0x14b/0x1f0 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd Freed by task 477: kasan_save_stack+0x1e/0x40 kasan_set_track+0x21/0x30 kasan_save_free_info+0x2a/0x50 __kasan_slab_free+0x10a/0x190 __kmem_cache_free+0xca/0x3f0 cifs_put_tcp_session+0x30c/0x450 cifs_mount+0xf95/0x1970 cifs_smb3_do_mount+0x295/0x1660 smb3_get_tree+0x352/0x5e0 vfs_get_tree+0x8e/0x2e0 path_mount+0xf8c/0x1990 do_mount+0xee/0x110 __x64_sys_mount+0x14b/0x1f0 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd The buggy address belongs to the object at ffff888108f35380 which belongs to the cache kmalloc-16 of size 16 The buggy address is located 0 bytes inside of 16-byte region [ffff888108f35380, ffff888108f35390) The buggy address belongs to the physical page: page:00000000333f8e58 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888108f350e0 pfn:0x108f35 flags: 0x200000000000200(slab|node=0|zone=2) raw: 0200000000000200 0000000000000000 dead000000000122 ffff8881000423c0 raw: ffff888108f350e0 000000008080007a 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888108f35280: fa fb fc fc fa fb fc fc fa fb fc fc fa fb fc fc ffff888108f35300: fa fb fc fc fa fb fc fc fa fb fc fc fa fb fc fc >ffff888108f35380: fa fb fc fc fa fb fc fc fa fb fc fc fa fb fc fc ^ ffff888108f35400: fa fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888108f35480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc Fixes: 7be3248f3139 ("cifs: To match file servers, make sure the server hostname matches") Signed-off-by: Zeng Heng Reviewed-by: Paulo Alcantara (SUSE) --- changes in v4: - correct fix tag - add reviewed-by --- fs/cifs/connect.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index ffb291579bb9..1cc47dd3b4d6 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -1584,6 +1584,7 @@ cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect) server->session_key.response = NULL; server->session_key.len = 0; kfree(server->hostname); + server->hostname = NULL; task = xchg(&server->tsk, NULL); if (task)