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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 0C68DC3276C for ; Thu, 2 Jan 2020 22:15:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C94FD24125 for ; Thu, 2 Jan 2020 22:15:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578003321; bh=uxom8iTWpOakVdNNsUARPsQP5eh5341Mmr3Z/419rTk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=mk0C49q0br6z3E8RnpHiGZRbvqYYcNvXHEh2w4f0tiaak+6tBokjRNFhYS3fDPWoA Zs07M4sBh84A0HUOYr3g8npCLuwz8IkMoYwOdYvo2q8IClRcxID4mztemPGMY0yYBm UoASSndI9+PMenuv4G0DABf0wp2INSqicz7wS7Hs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728057AbgABWPU (ORCPT ); Thu, 2 Jan 2020 17:15:20 -0500 Received: from mail.kernel.org ([198.145.29.99]:55986 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728035AbgABWPQ (ORCPT ); Thu, 2 Jan 2020 17:15:16 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6409521582; Thu, 2 Jan 2020 22:15:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578003315; bh=uxom8iTWpOakVdNNsUARPsQP5eh5341Mmr3Z/419rTk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=A+shXVpwlalXuzZKg5DuLBaQzg48oSn9CtPTW17jgYT1I97Gxfl81y/Iw0uqMtgK5 GmVLhu5OdX7GaNgFIw7Tg8D2KsaJ3MGAEo2OOIzAtEh7LDv5sGEaIooCxYfw0WgDse T5BJW7VVVYFFMUSoTdiP9wQsuLPDmiHJoIFLBSBg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Paulo Alcantara (SUSE)" , Aurelien Aptel , Steve French , Sasha Levin Subject: [PATCH 5.4 109/191] cifs: Fix use-after-free bug in cifs_reconnect() Date: Thu, 2 Jan 2020 23:06:31 +0100 Message-Id: <20200102215841.573615222@linuxfoundation.org> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200102215829.911231638@linuxfoundation.org> References: <20200102215829.911231638@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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 20c70cbab1ad..02451d085ddd 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