From patchwork Fri Nov 22 15:30:51 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paulo Alcantara X-Patchwork-Id: 11258103 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8140C14DB for ; Fri, 22 Nov 2019 15:31:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 575E220715 for ; Fri, 22 Nov 2019 15:31:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=cjr.nz header.i=@cjr.nz header.b="zVuO94Tu" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726664AbfKVPbe (ORCPT ); Fri, 22 Nov 2019 10:31:34 -0500 Received: from mx.cjr.nz ([51.158.111.142]:28294 "EHLO mx.cjr.nz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726568AbfKVPbd (ORCPT ); Fri, 22 Nov 2019 10:31:33 -0500 Received: from authenticated-user (mx.cjr.nz [51.158.111.142]) (Authenticated sender: pc) by mx.cjr.nz (Postfix) with ESMTPSA id 5F27380A50; Fri, 22 Nov 2019 15:31:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cjr.nz; s=dkim; t=1574436690; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+U76RSc9sQIDDsga0pX9LsYIubLGxmziIpfX2TaXmfg=; b=zVuO94TuT9wZy5iV1zA/4NZSWP/A9Osm0ZO0aaztOxIz8TshHKzCAT99CaHP/KnzF/RJ5N HZs5kUY3YsUjpl2BQFgJWoZ8T0c1hHG0Q0TUMdIgG4yuyt17zLtGRY3mqeFRnCfNK/iXJI 59rQk8p7Hsq8Vaul8KHLbVoZE3iea+d2NkIeYcQIootGm+Avs4bLmB1HE12uPq3FdNsawE 1NuhSFryz2SkaViaSwiTJONiXT2NKj4xl85tHTL4ojN8ipYHDWrh3cMWk1h99PQyX5lToF vqX6LV3BVRwM5FZziwoeiQ4rG14Ya2+7cV7bsxeJsBvBupMzr7oSpb6eaM4MaA== From: "Paulo Alcantara (SUSE)" To: smfrench@gmail.com Cc: linux-cifs@vger.kernel.org, "Paulo Alcantara (SUSE)" Subject: [PATCH 1/7] cifs: Fix use-after-free bug in cifs_reconnect() Date: Fri, 22 Nov 2019 12:30:51 -0300 Message-Id: <20191122153057.6608-2-pc@cjr.nz> In-Reply-To: <20191122153057.6608-1-pc@cjr.nz> References: <20191122153057.6608-1-pc@cjr.nz> MIME-Version: 1.0 Sender: linux-cifs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org Ensure we grab an active reference in cifs superblock while doing failover to prevent automounts (DFS links) of expiring and then destroying the superblock pointer. This patch fixes the following KASAN report: [ 464.301462] BUG: KASAN: use-after-free in cifs_reconnect+0x6ab/0x1350 [ 464.303052] Read of size 8 at addr ffff888155e580d0 by task cifsd/1107 [ 464.304682] CPU: 3 PID: 1107 Comm: cifsd Not tainted 5.4.0-rc4+ #13 [ 464.305552] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.1-0-ga5cab58-rebuilt.opensuse.org 04/01/2014 [ 464.307146] Call Trace: [ 464.307875] dump_stack+0x5b/0x90 [ 464.308631] print_address_description.constprop.0+0x16/0x200 [ 464.309478] ? cifs_reconnect+0x6ab/0x1350 [ 464.310253] ? cifs_reconnect+0x6ab/0x1350 [ 464.311040] __kasan_report.cold+0x1a/0x41 [ 464.311811] ? cifs_reconnect+0x6ab/0x1350 [ 464.312563] kasan_report+0xe/0x20 [ 464.313300] cifs_reconnect+0x6ab/0x1350 [ 464.314062] ? extract_hostname.part.0+0x90/0x90 [ 464.314829] ? printk+0xad/0xde [ 464.315525] ? _raw_spin_lock+0x7c/0xd0 [ 464.316252] ? _raw_read_lock_irq+0x40/0x40 [ 464.316961] ? ___ratelimit+0xed/0x182 [ 464.317655] cifs_readv_from_socket+0x289/0x3b0 [ 464.318386] cifs_read_from_socket+0x98/0xd0 [ 464.319078] ? cifs_readv_from_socket+0x3b0/0x3b0 [ 464.319782] ? try_to_wake_up+0x43c/0xa90 [ 464.320463] ? cifs_small_buf_get+0x4b/0x60 [ 464.321173] ? allocate_buffers+0x98/0x1a0 [ 464.321856] cifs_demultiplex_thread+0x218/0x14a0 [ 464.322558] ? cifs_handle_standard+0x270/0x270 [ 464.323237] ? __switch_to_asm+0x40/0x70 [ 464.323893] ? __switch_to_asm+0x34/0x70 [ 464.324554] ? __switch_to_asm+0x40/0x70 [ 464.325226] ? __switch_to_asm+0x40/0x70 [ 464.325863] ? __switch_to_asm+0x34/0x70 [ 464.326505] ? __switch_to_asm+0x40/0x70 [ 464.327161] ? __switch_to_asm+0x34/0x70 [ 464.327784] ? finish_task_switch+0xa1/0x330 [ 464.328414] ? __switch_to+0x363/0x640 [ 464.329044] ? __schedule+0x575/0xaf0 [ 464.329655] ? _raw_spin_lock_irqsave+0x82/0xe0 [ 464.330301] kthread+0x1a3/0x1f0 [ 464.330884] ? cifs_handle_standard+0x270/0x270 [ 464.331624] ? kthread_create_on_node+0xd0/0xd0 [ 464.332347] ret_from_fork+0x35/0x40 [ 464.333577] Allocated by task 1110: [ 464.334381] save_stack+0x1b/0x80 [ 464.335123] __kasan_kmalloc.constprop.0+0xc2/0xd0 [ 464.335848] cifs_smb3_do_mount+0xd4/0xb00 [ 464.336619] legacy_get_tree+0x6b/0xa0 [ 464.337235] vfs_get_tree+0x41/0x110 [ 464.337975] fc_mount+0xa/0x40 [ 464.338557] vfs_kern_mount.part.0+0x6c/0x80 [ 464.339227] cifs_dfs_d_automount+0x336/0xd29 [ 464.339846] follow_managed+0x1b1/0x450 [ 464.340449] lookup_fast+0x231/0x4a0 [ 464.341039] path_openat+0x240/0x1fd0 [ 464.341634] do_filp_open+0x126/0x1c0 [ 464.342277] do_sys_open+0x1eb/0x2c0 [ 464.342957] do_syscall_64+0x5e/0x190 [ 464.343555] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 464.344772] Freed by task 0: [ 464.345347] save_stack+0x1b/0x80 [ 464.345966] __kasan_slab_free+0x12c/0x170 [ 464.346576] kfree+0xa6/0x270 [ 464.347211] rcu_core+0x39c/0xc80 [ 464.347800] __do_softirq+0x10d/0x3da [ 464.348919] The buggy address belongs to the object at ffff888155e58000 which belongs to the cache kmalloc-256 of size 256 [ 464.350222] The buggy address is located 208 bytes inside of 256-byte region [ffff888155e58000, ffff888155e58100) [ 464.351575] The buggy address belongs to the page: [ 464.352333] page:ffffea0005579600 refcount:1 mapcount:0 mapping:ffff88815a803400 index:0x0 compound_mapcount: 0 [ 464.353583] flags: 0x200000000010200(slab|head) [ 464.354209] raw: 0200000000010200 ffffea0005576200 0000000400000004 ffff88815a803400 [ 464.355353] raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000 [ 464.356458] page dumped because: kasan: bad access detected [ 464.367005] Memory state around the buggy address: [ 464.367787] ffff888155e57f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 464.368877] ffff888155e58000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 464.369967] >ffff888155e58080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 464.371111] ^ [ 464.371775] ffff888155e58100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 464.372893] ffff888155e58180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 464.373983] ================================================================== Signed-off-by: Paulo Alcantara (SUSE) Reviewed-by: Aurelien Aptel --- fs/cifs/connect.c | 46 +++++++++++++++++++++++++++++++++++----------- 1 file changed, 35 insertions(+), 11 deletions(-) diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index fce71a6cc3f4..668d477cc9c7 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -391,7 +391,7 @@ static inline int reconn_set_ipaddr(struct TCP_Server_Info *server) #ifdef CONFIG_CIFS_DFS_UPCALL struct super_cb_data { struct TCP_Server_Info *server; - struct cifs_sb_info *cifs_sb; + struct super_block *sb; }; /* These functions must be called with server->srv_mutex held */ @@ -402,25 +402,39 @@ static void super_cb(struct super_block *sb, void *arg) struct cifs_sb_info *cifs_sb; struct cifs_tcon *tcon; - if (d->cifs_sb) + if (d->sb) return; cifs_sb = CIFS_SB(sb); tcon = cifs_sb_master_tcon(cifs_sb); if (tcon->ses->server == d->server) - d->cifs_sb = cifs_sb; + d->sb = sb; } -static inline struct cifs_sb_info * -find_super_by_tcp(struct TCP_Server_Info *server) +static struct super_block *get_tcp_super(struct TCP_Server_Info *server) { struct super_cb_data d = { .server = server, - .cifs_sb = NULL, + .sb = NULL, }; iterate_supers_type(&cifs_fs_type, super_cb, &d); - return d.cifs_sb ? d.cifs_sb : ERR_PTR(-ENOENT); + + if (unlikely(!d.sb)) + return ERR_PTR(-ENOENT); + /* + * Grab an active reference in order to prevent automounts (DFS links) + * of expiring and then freeing up our cifs superblock pointer while + * we're doing failover. + */ + cifs_sb_active(d.sb); + return d.sb; +} + +static inline void put_tcp_super(struct super_block *sb) +{ + if (!IS_ERR_OR_NULL(sb)) + cifs_sb_deactive(sb); } static void reconn_inval_dfs_target(struct TCP_Server_Info *server, @@ -484,6 +498,7 @@ cifs_reconnect(struct TCP_Server_Info *server) struct mid_q_entry *mid_entry; struct list_head retry_list; #ifdef CONFIG_CIFS_DFS_UPCALL + struct super_block *sb = NULL; struct cifs_sb_info *cifs_sb = NULL; struct dfs_cache_tgt_list tgt_list = {0}; struct dfs_cache_tgt_iterator *tgt_it = NULL; @@ -493,13 +508,15 @@ cifs_reconnect(struct TCP_Server_Info *server) server->nr_targets = 1; #ifdef CONFIG_CIFS_DFS_UPCALL spin_unlock(&GlobalMid_Lock); - cifs_sb = find_super_by_tcp(server); - if (IS_ERR(cifs_sb)) { - rc = PTR_ERR(cifs_sb); + sb = get_tcp_super(server); + if (IS_ERR(sb)) { + rc = PTR_ERR(sb); cifs_dbg(FYI, "%s: will not do DFS failover: rc = %d\n", __func__, rc); - cifs_sb = NULL; + sb = NULL; } else { + cifs_sb = CIFS_SB(sb); + rc = reconn_setup_dfs_targets(cifs_sb, &tgt_list, &tgt_it); if (rc && (rc != -EOPNOTSUPP)) { cifs_server_dbg(VFS, "%s: no target servers for DFS failover\n", @@ -516,6 +533,10 @@ cifs_reconnect(struct TCP_Server_Info *server) /* the demux thread will exit normally next time through the loop */ spin_unlock(&GlobalMid_Lock); +#ifdef CONFIG_CIFS_DFS_UPCALL + dfs_cache_free_tgts(&tgt_list); + put_tcp_super(sb); +#endif return rc; } else server->tcpStatus = CifsNeedReconnect; @@ -642,7 +663,10 @@ cifs_reconnect(struct TCP_Server_Info *server) __func__, rc); } dfs_cache_free_tgts(&tgt_list); + } + + put_tcp_super(sb); #endif if (server->tcpStatus == CifsNeedNegotiate) mod_delayed_work(cifsiod_wq, &server->echo, 0);