From: "Paulo Alcantara (SUSE)" <pc@cjr.nz>
To: smfrench@gmail.com
Cc: linux-cifs@vger.kernel.org, "Paulo Alcantara (SUSE)" <pc@cjr.nz>,
Aurelien Aptel <aaptel@suse.com>
Subject: [PATCH v3 01/11] cifs: Fix use-after-free bug in cifs_reconnect()
Date: Tue, 26 Nov 2019 21:36:24 -0300 [thread overview]
Message-ID: <20191127003634.14072-2-pc@cjr.nz> (raw)
In-Reply-To: <20191127003634.14072-1-pc@cjr.nz>
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) <pc@cjr.nz>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
---
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);
--
2.24.0
next prev parent reply other threads:[~2019-11-27 0:37 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-27 0:36 [PATCH v3 00/11] DFS fixes Paulo Alcantara (SUSE)
2019-11-27 0:36 ` Paulo Alcantara (SUSE) [this message]
2019-11-27 0:36 ` [PATCH v3 02/11] cifs: Fix lookup of root ses in DFS referral cache Paulo Alcantara (SUSE)
2019-11-27 0:36 ` [PATCH v3 03/11] cifs: Fix potential softlockups while refreshing DFS cache Paulo Alcantara (SUSE)
2019-11-27 0:36 ` [PATCH v3 04/11] cifs: Clean up DFS referral cache Paulo Alcantara (SUSE)
2019-11-27 11:32 ` Aurélien Aptel
2019-11-27 0:36 ` [PATCH v3 05/11] cifs: Get rid of kstrdup_const()'d paths Paulo Alcantara (SUSE)
2019-11-27 11:33 ` Aurélien Aptel
2019-11-27 0:36 ` [PATCH v3 06/11] cifs: Introduce helpers for finding TCP connection Paulo Alcantara (SUSE)
2019-11-27 11:33 ` Aurélien Aptel
2019-11-27 0:36 ` [PATCH v3 07/11] cifs: Merge is_path_valid() into get_normalized_path() Paulo Alcantara (SUSE)
2019-11-27 11:34 ` Aurélien Aptel
2019-11-27 0:36 ` [PATCH v3 08/11] cifs: Fix potential deadlock when updating vol in cifs_reconnect() Paulo Alcantara (SUSE)
2019-11-27 12:09 ` Aurélien Aptel
2019-11-27 0:36 ` [PATCH v3 09/11] cifs: Avoid doing network I/O while holding cache lock Paulo Alcantara (SUSE)
2019-11-27 13:32 ` Aurélien Aptel
2019-11-27 0:36 ` [PATCH v3 10/11] cifs: Fix retrieval of DFS referrals in cifs_mount() Paulo Alcantara (SUSE)
2019-11-27 13:33 ` Aurélien Aptel
2019-11-27 0:36 ` [PATCH v3 11/11] cifs: Always update signing key of first channel Paulo Alcantara (SUSE)
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