From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A6B25C00454 for ; Wed, 11 Dec 2019 15:57:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 66A132073B for ; Wed, 11 Dec 2019 15:57:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576079866; bh=T2ak9Jiibb0uzXEBWffIWdRs2ALQSArJoWVAoJ5rDSA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=2jzjnNIV5aC7BRYEsZbf6+XAaikNPsr1vZKaba/ZuPmnpBMOlWICuzC+66ksUU9Ll j+RuPpb7831lGYLEZjK/gqc3eRnyH9KHiSrlFiXtrKZJYGAFw6Qz/8NzPqIShp45l3 AEgPjlaM2hhRiBGINSkdeRMKBCtLyZ+bU1AMOcxY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731688AbfLKPO5 (ORCPT ); Wed, 11 Dec 2019 10:14:57 -0500 Received: from mail.kernel.org ([198.145.29.99]:38218 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731524AbfLKPN4 (ORCPT ); Wed, 11 Dec 2019 10:13:56 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1EAF424681; Wed, 11 Dec 2019 15:13:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576077234; bh=T2ak9Jiibb0uzXEBWffIWdRs2ALQSArJoWVAoJ5rDSA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mvTlC7rC7kksx6/dheTl6BzZNG2WlbQG66t8iO8SZptHGu8xGtoNiI0YVoLUizxXM Lgx7K3nGej3DBR9VFDSjfqWUI+tsUxR2P3Nv585x2ZwH4AP79EXznQdKaJ+WehEI/j jLHdwlsyDUtuiHJgqJDGeA6dGY9NXfsONdNrx+RU= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Paulo Alcantara (SUSE)" , Aurelien Aptel , Steve French , Sasha Levin , linux-cifs@vger.kernel.org, samba-technical@lists.samba.org Subject: [PATCH AUTOSEL 5.4 113/134] cifs: Fix use-after-free bug in cifs_reconnect() Date: Wed, 11 Dec 2019 10:11:29 -0500 Message-Id: <20191211151150.19073-113-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191211151150.19073-1-sashal@kernel.org> References: <20191211151150.19073-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paulo Alcantara (SUSE)" [ Upstream commit 8354d88efdab72b4da32fc4f032448fcef22dab4 ] 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 Signed-off-by: Steve French Signed-off-by: Sasha Levin --- 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 ccaa8bad336f9..a4ae4d944a3ab 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -387,7 +387,7 @@ 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 */ @@ -398,25 +398,39 @@ 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, @@ -480,6 +494,7 @@ 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; @@ -489,13 +504,15 @@ 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", @@ -512,6 +529,10 @@ 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; @@ -638,7 +659,10 @@ 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); -- 2.20.1