CIFS: Fix a possible memory corruption during reconnect
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. CC: Stable <stable@vger.kernel.org> Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
This commit is contained in:
Pavel Shilovsky
parent
e3d240e9d5
commit
53e0e11efe
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@ -647,6 +647,8 @@ struct TCP_Server_Info {
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unsigned int max_read;
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unsigned int max_write;
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__u8 preauth_hash[512];
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struct delayed_work reconnect; /* reconnect workqueue job */
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struct mutex reconnect_mutex; /* prevent simultaneous reconnects */
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#endif /* CONFIG_CIFS_SMB2 */
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unsigned long echo_interval;
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};
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@ -850,6 +852,7 @@ cap_unix(struct cifs_ses *ses)
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struct cifs_tcon {
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struct list_head tcon_list;
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int tc_count;
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struct list_head rlist; /* reconnect list */
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struct list_head openFileList;
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spinlock_t open_file_lock; /* protects list above */
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struct cifs_ses *ses; /* pointer to session associated with */
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@ -206,6 +206,9 @@ extern void cifs_add_pending_open_locked(struct cifs_fid *fid,
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struct tcon_link *tlink,
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struct cifs_pending_open *open);
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extern void cifs_del_pending_open(struct cifs_pending_open *open);
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extern void cifs_put_tcp_session(struct TCP_Server_Info *server,
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int from_reconnect);
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extern void cifs_put_tcon(struct cifs_tcon *tcon);
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#if IS_ENABLED(CONFIG_CIFS_DFS_UPCALL)
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extern void cifs_dfs_release_automount_timer(void);
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@ -52,6 +52,9 @@
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#include "nterr.h"
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#include "rfc1002pdu.h"
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#include "fscache.h"
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#ifdef CONFIG_CIFS_SMB2
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#include "smb2proto.h"
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#endif
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#define CIFS_PORT 445
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#define RFC1001_PORT 139
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@ -2110,8 +2113,8 @@ cifs_find_tcp_session(struct smb_vol *vol)
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return NULL;
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}
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static void
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cifs_put_tcp_session(struct TCP_Server_Info *server)
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void
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cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect)
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{
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struct task_struct *task;
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@ -2128,6 +2131,19 @@ cifs_put_tcp_session(struct TCP_Server_Info *server)
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cancel_delayed_work_sync(&server->echo);
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#ifdef CONFIG_CIFS_SMB2
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if (from_reconnect)
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/*
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* Avoid deadlock here: reconnect work calls
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* cifs_put_tcp_session() at its end. Need to be sure
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* that reconnect work does nothing with server pointer after
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* that step.
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*/
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cancel_delayed_work(&server->reconnect);
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else
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cancel_delayed_work_sync(&server->reconnect);
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#endif
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spin_lock(&GlobalMid_Lock);
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server->tcpStatus = CifsExiting;
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spin_unlock(&GlobalMid_Lock);
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@ -2192,6 +2208,10 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
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INIT_LIST_HEAD(&tcp_ses->tcp_ses_list);
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INIT_LIST_HEAD(&tcp_ses->smb_ses_list);
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INIT_DELAYED_WORK(&tcp_ses->echo, cifs_echo_request);
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#ifdef CONFIG_CIFS_SMB2
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INIT_DELAYED_WORK(&tcp_ses->reconnect, smb2_reconnect_server);
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mutex_init(&tcp_ses->reconnect_mutex);
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#endif
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memcpy(&tcp_ses->srcaddr, &volume_info->srcaddr,
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sizeof(tcp_ses->srcaddr));
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memcpy(&tcp_ses->dstaddr, &volume_info->dstaddr,
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@ -2350,7 +2370,7 @@ cifs_put_smb_ses(struct cifs_ses *ses)
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spin_unlock(&cifs_tcp_ses_lock);
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sesInfoFree(ses);
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cifs_put_tcp_session(server);
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cifs_put_tcp_session(server, 0);
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}
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#ifdef CONFIG_KEYS
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@ -2524,7 +2544,7 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb_vol *volume_info)
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mutex_unlock(&ses->session_mutex);
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/* existing SMB ses has a server reference already */
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cifs_put_tcp_session(server);
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cifs_put_tcp_session(server, 0);
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free_xid(xid);
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return ses;
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}
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@ -2620,7 +2640,7 @@ cifs_find_tcon(struct cifs_ses *ses, struct smb_vol *volume_info)
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return NULL;
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}
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static void
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void
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cifs_put_tcon(struct cifs_tcon *tcon)
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{
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unsigned int xid;
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@ -3824,7 +3844,7 @@ mount_fail_check:
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else if (ses)
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cifs_put_smb_ses(ses);
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else
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cifs_put_tcp_session(server);
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cifs_put_tcp_session(server, 0);
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bdi_destroy(&cifs_sb->bdi);
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}
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@ -4135,7 +4155,7 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
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ses = cifs_get_smb_ses(master_tcon->ses->server, vol_info);
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if (IS_ERR(ses)) {
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tcon = (struct cifs_tcon *)ses;
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cifs_put_tcp_session(master_tcon->ses->server);
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cifs_put_tcp_session(master_tcon->ses->server, 0);
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goto out;
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}
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@ -1972,6 +1972,54 @@ smb2_echo_callback(struct mid_q_entry *mid)
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add_credits(server, credits_received, CIFS_ECHO_OP);
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}
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void smb2_reconnect_server(struct work_struct *work)
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{
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struct TCP_Server_Info *server = container_of(work,
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struct TCP_Server_Info, reconnect.work);
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struct cifs_ses *ses;
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struct cifs_tcon *tcon, *tcon2;
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struct list_head tmp_list;
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int tcon_exist = false;
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/* Prevent simultaneous reconnects that can corrupt tcon->rlist list */
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mutex_lock(&server->reconnect_mutex);
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INIT_LIST_HEAD(&tmp_list);
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cifs_dbg(FYI, "Need negotiate, reconnecting tcons\n");
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spin_lock(&cifs_tcp_ses_lock);
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list_for_each_entry(ses, &server->smb_ses_list, smb_ses_list) {
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list_for_each_entry(tcon, &ses->tcon_list, tcon_list) {
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if (tcon->need_reconnect) {
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tcon->tc_count++;
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list_add_tail(&tcon->rlist, &tmp_list);
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tcon_exist = true;
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}
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}
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}
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/*
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* Get the reference to server struct to be sure that the last call of
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* cifs_put_tcon() in the loop below won't release the server pointer.
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*/
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if (tcon_exist)
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server->srv_count++;
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spin_unlock(&cifs_tcp_ses_lock);
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list_for_each_entry_safe(tcon, tcon2, &tmp_list, rlist) {
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smb2_reconnect(SMB2_ECHO, tcon);
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list_del_init(&tcon->rlist);
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cifs_put_tcon(tcon);
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}
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cifs_dbg(FYI, "Reconnecting tcons finished\n");
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mutex_unlock(&server->reconnect_mutex);
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/* now we can safely release srv struct */
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if (tcon_exist)
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cifs_put_tcp_session(server, 1);
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}
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int
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SMB2_echo(struct TCP_Server_Info *server)
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{
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@ -1984,32 +2032,11 @@ SMB2_echo(struct TCP_Server_Info *server)
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cifs_dbg(FYI, "In echo request\n");
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if (server->tcpStatus == CifsNeedNegotiate) {
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struct list_head *tmp, *tmp2;
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struct cifs_ses *ses;
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struct cifs_tcon *tcon;
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cifs_dbg(FYI, "Need negotiate, reconnecting tcons\n");
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spin_lock(&cifs_tcp_ses_lock);
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list_for_each(tmp, &server->smb_ses_list) {
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ses = list_entry(tmp, struct cifs_ses, smb_ses_list);
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list_for_each(tmp2, &ses->tcon_list) {
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tcon = list_entry(tmp2, struct cifs_tcon,
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tcon_list);
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/* add check for persistent handle reconnect */
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if (tcon && tcon->need_reconnect) {
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spin_unlock(&cifs_tcp_ses_lock);
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rc = smb2_reconnect(SMB2_ECHO, tcon);
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spin_lock(&cifs_tcp_ses_lock);
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}
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}
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}
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spin_unlock(&cifs_tcp_ses_lock);
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/* No need to send echo on newly established connections */
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queue_delayed_work(cifsiod_wq, &server->reconnect, 0);
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return rc;
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}
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/* if no session, renegotiate failed above */
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if (server->tcpStatus == CifsNeedNegotiate)
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return -EIO;
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rc = small_smb2_init(SMB2_ECHO, NULL, (void **)&req);
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if (rc)
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return rc;
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@ -96,6 +96,7 @@ extern int smb2_open_file(const unsigned int xid,
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extern int smb2_unlock_range(struct cifsFileInfo *cfile,
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struct file_lock *flock, const unsigned int xid);
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extern int smb2_push_mandatory_locks(struct cifsFileInfo *cfile);
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extern void smb2_reconnect_server(struct work_struct *work);
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/*
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* SMB2 Worker functions - most of protocol specific implementation details
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