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Message-ID: <lsq.1489146382.599729094@decadent.org.uk>
Date: Fri, 10 Mar 2017 11:46:22 +0000
From: Ben Hutchings <ben@...adent.org.uk>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC: akpm@...ux-foundation.org,
"Pavel Shilovsky" <pshilov@...rosoft.com>
Subject: [PATCH 3.16 074/370] CIFS: Fix a possible memory corruption
during reconnect
3.16.42-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Pavel Shilovsky <pshilov@...rosoft.com>
commit 53e0e11efe9289535b060a51d4cf37c25e0d0f2b upstream.
We can not unlock/lock cifs_tcp_ses_lock while walking through ses
and tcon lists because it can corrupt list iterator pointers and
a tcon structure can be released if we don't hold an extra reference.
Fix it by moving a reconnect process to a separate delayed work
and acquiring a reference to every tcon that needs to be reconnected.
Also do not send an echo request on newly established connections.
Signed-off-by: Pavel Shilovsky <pshilov@...rosoft.com>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
fs/cifs/cifsglob.h | 3 +++
fs/cifs/cifsproto.h | 3 +++
fs/cifs/connect.c | 34 +++++++++++++++++++-----
fs/cifs/smb2pdu.c | 75 ++++++++++++++++++++++++++++++++++++-----------------
fs/cifs/smb2proto.h | 1 +
5 files changed, 85 insertions(+), 31 deletions(-)
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -606,6 +606,8 @@ struct TCP_Server_Info {
#ifdef CONFIG_CIFS_SMB2
unsigned int max_read;
unsigned int max_write;
+ struct delayed_work reconnect; /* reconnect workqueue job */
+ struct mutex reconnect_mutex; /* prevent simultaneous reconnects */
#endif /* CONFIG_CIFS_SMB2 */
};
@@ -795,6 +797,7 @@ cap_unix(struct cifs_ses *ses)
struct cifs_tcon {
struct list_head tcon_list;
int tc_count;
+ struct list_head rlist; /* reconnect list */
struct list_head openFileList;
spinlock_t open_file_lock; /* protects list above */
struct cifs_ses *ses; /* pointer to session associated with */
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -203,6 +203,9 @@ extern void cifs_add_pending_open_locked
struct tcon_link *tlink,
struct cifs_pending_open *open);
extern void cifs_del_pending_open(struct cifs_pending_open *open);
+extern void cifs_put_tcp_session(struct TCP_Server_Info *server,
+ int from_reconnect);
+extern void cifs_put_tcon(struct cifs_tcon *tcon);
#if IS_ENABLED(CONFIG_CIFS_DFS_UPCALL)
extern void cifs_dfs_release_automount_timer(void);
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -52,6 +52,9 @@
#include "nterr.h"
#include "rfc1002pdu.h"
#include "fscache.h"
+#ifdef CONFIG_CIFS_SMB2
+#include "smb2proto.h"
+#endif
#define CIFS_PORT 445
#define RFC1001_PORT 139
@@ -2060,8 +2063,8 @@ cifs_find_tcp_session(struct smb_vol *vo
return NULL;
}
-static void
-cifs_put_tcp_session(struct TCP_Server_Info *server)
+void
+cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect)
{
struct task_struct *task;
@@ -2078,6 +2081,19 @@ cifs_put_tcp_session(struct TCP_Server_I
cancel_delayed_work_sync(&server->echo);
+#ifdef CONFIG_CIFS_SMB2
+ if (from_reconnect)
+ /*
+ * Avoid deadlock here: reconnect work calls
+ * cifs_put_tcp_session() at its end. Need to be sure
+ * that reconnect work does nothing with server pointer after
+ * that step.
+ */
+ cancel_delayed_work(&server->reconnect);
+ else
+ cancel_delayed_work_sync(&server->reconnect);
+#endif
+
spin_lock(&GlobalMid_Lock);
server->tcpStatus = CifsExiting;
spin_unlock(&GlobalMid_Lock);
@@ -2142,6 +2158,10 @@ cifs_get_tcp_session(struct smb_vol *vol
INIT_LIST_HEAD(&tcp_ses->tcp_ses_list);
INIT_LIST_HEAD(&tcp_ses->smb_ses_list);
INIT_DELAYED_WORK(&tcp_ses->echo, cifs_echo_request);
+#ifdef CONFIG_CIFS_SMB2
+ INIT_DELAYED_WORK(&tcp_ses->reconnect, smb2_reconnect_server);
+ mutex_init(&tcp_ses->reconnect_mutex);
+#endif
memcpy(&tcp_ses->srcaddr, &volume_info->srcaddr,
sizeof(tcp_ses->srcaddr));
memcpy(&tcp_ses->dstaddr, &volume_info->dstaddr,
@@ -2294,7 +2314,7 @@ cifs_put_smb_ses(struct cifs_ses *ses)
spin_unlock(&cifs_tcp_ses_lock);
sesInfoFree(ses);
- cifs_put_tcp_session(server);
+ cifs_put_tcp_session(server, 0);
}
#ifdef CONFIG_KEYS
@@ -2467,7 +2487,7 @@ cifs_get_smb_ses(struct TCP_Server_Info
mutex_unlock(&ses->session_mutex);
/* existing SMB ses has a server reference already */
- cifs_put_tcp_session(server);
+ cifs_put_tcp_session(server, 0);
free_xid(xid);
return ses;
}
@@ -2557,7 +2577,7 @@ cifs_find_tcon(struct cifs_ses *ses, con
return NULL;
}
-static void
+void
cifs_put_tcon(struct cifs_tcon *tcon)
{
unsigned int xid;
@@ -3606,7 +3626,7 @@ mount_fail_check:
else if (ses)
cifs_put_smb_ses(ses);
else
- cifs_put_tcp_session(server);
+ cifs_put_tcp_session(server, 0);
bdi_destroy(&cifs_sb->bdi);
}
@@ -3910,7 +3930,7 @@ cifs_construct_tcon(struct cifs_sb_info
ses = cifs_get_smb_ses(master_tcon->ses->server, vol_info);
if (IS_ERR(ses)) {
tcon = (struct cifs_tcon *)ses;
- cifs_put_tcp_session(master_tcon->ses->server);
+ cifs_put_tcp_session(master_tcon->ses->server, 0);
goto out;
}
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -1598,6 +1598,54 @@ smb2_echo_callback(struct mid_q_entry *m
add_credits(server, credits_received, CIFS_ECHO_OP);
}
+void smb2_reconnect_server(struct work_struct *work)
+{
+ struct TCP_Server_Info *server = container_of(work,
+ struct TCP_Server_Info, reconnect.work);
+ struct cifs_ses *ses;
+ struct cifs_tcon *tcon, *tcon2;
+ struct list_head tmp_list;
+ int tcon_exist = false;
+
+ /* Prevent simultaneous reconnects that can corrupt tcon->rlist list */
+ mutex_lock(&server->reconnect_mutex);
+
+ INIT_LIST_HEAD(&tmp_list);
+ cifs_dbg(FYI, "Need negotiate, reconnecting tcons\n");
+
+ spin_lock(&cifs_tcp_ses_lock);
+ list_for_each_entry(ses, &server->smb_ses_list, smb_ses_list) {
+ list_for_each_entry(tcon, &ses->tcon_list, tcon_list) {
+ if (tcon->need_reconnect) {
+ tcon->tc_count++;
+ list_add_tail(&tcon->rlist, &tmp_list);
+ tcon_exist = true;
+ }
+ }
+ }
+ /*
+ * Get the reference to server struct to be sure that the last call of
+ * cifs_put_tcon() in the loop below won't release the server pointer.
+ */
+ if (tcon_exist)
+ server->srv_count++;
+
+ spin_unlock(&cifs_tcp_ses_lock);
+
+ list_for_each_entry_safe(tcon, tcon2, &tmp_list, rlist) {
+ smb2_reconnect(SMB2_ECHO, tcon);
+ list_del_init(&tcon->rlist);
+ cifs_put_tcon(tcon);
+ }
+
+ cifs_dbg(FYI, "Reconnecting tcons finished\n");
+ mutex_unlock(&server->reconnect_mutex);
+
+ /* now we can safely release srv struct */
+ if (tcon_exist)
+ cifs_put_tcp_session(server, 1);
+}
+
int
SMB2_echo(struct TCP_Server_Info *server)
{
@@ -1610,32 +1658,11 @@ SMB2_echo(struct TCP_Server_Info *server
cifs_dbg(FYI, "In echo request\n");
if (server->tcpStatus == CifsNeedNegotiate) {
- struct list_head *tmp, *tmp2;
- struct cifs_ses *ses;
- struct cifs_tcon *tcon;
-
- cifs_dbg(FYI, "Need negotiate, reconnecting tcons\n");
- spin_lock(&cifs_tcp_ses_lock);
- list_for_each(tmp, &server->smb_ses_list) {
- ses = list_entry(tmp, struct cifs_ses, smb_ses_list);
- list_for_each(tmp2, &ses->tcon_list) {
- tcon = list_entry(tmp2, struct cifs_tcon,
- tcon_list);
- /* add check for persistent handle reconnect */
- if (tcon && tcon->need_reconnect) {
- spin_unlock(&cifs_tcp_ses_lock);
- rc = smb2_reconnect(SMB2_ECHO, tcon);
- spin_lock(&cifs_tcp_ses_lock);
- }
- }
- }
- spin_unlock(&cifs_tcp_ses_lock);
+ /* No need to send echo on newly established connections */
+ queue_delayed_work(cifsiod_wq, &server->reconnect, 0);
+ return rc;
}
- /* if no session, renegotiate failed above */
- if (server->tcpStatus == CifsNeedNegotiate)
- return -EIO;
-
rc = small_smb2_init(SMB2_ECHO, NULL, (void **)&req);
if (rc)
return rc;
--- a/fs/cifs/smb2proto.h
+++ b/fs/cifs/smb2proto.h
@@ -89,6 +89,7 @@ extern int smb2_open_file(const unsigned
extern int smb2_unlock_range(struct cifsFileInfo *cfile,
struct file_lock *flock, const unsigned int xid);
extern int smb2_push_mandatory_locks(struct cifsFileInfo *cfile);
+extern void smb2_reconnect_server(struct work_struct *work);
/*
* SMB2 Worker functions - most of protocol specific implementation details
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