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Commit 53e0e11e authored by Pavel Shilovsky's avatar Pavel Shilovsky
Browse files

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: default avatarPavel Shilovsky <pshilov@microsoft.com>
parent e3d240e9

fs/cifs/cifsglob.h

+3 −0
Original line number Diff line number Diff line
@@ -647,6 +647,8 @@ struct TCP_Server_Info { 
	unsigned int	max_read;

	unsigned int	max_write;

	__u8		preauth_hash[512];

	struct delayed_work reconnect; /* reconnect workqueue job */

	struct mutex reconnect_mutex; /* prevent simultaneous reconnects */

#endif /* CONFIG_CIFS_SMB2 */

	unsigned long echo_interval;

};
@@ -850,6 +852,7 @@ 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 */

fs/cifs/cifsproto.h

+3 −0
Original line number Diff line number Diff line
@@ -206,6 +206,9 @@ extern void cifs_add_pending_open_locked(struct cifs_fid *fid, 
					 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);

fs/cifs/connect.c

+27 −7
Original line number Diff line number Diff line
@@ -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
@@ -2110,8 +2113,8 @@ cifs_find_tcp_session(struct smb_vol *vol) 
	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;
@@ -2128,6 +2131,19 @@ cifs_put_tcp_session(struct TCP_Server_Info *server) 


	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);
@@ -2192,6 +2208,10 @@ cifs_get_tcp_session(struct smb_vol *volume_info) 
	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,
@@ -2350,7 +2370,7 @@ 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
@@ -2524,7 +2544,7 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb_vol *volume_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;

	}
@@ -2620,7 +2640,7 @@ cifs_find_tcon(struct cifs_ses *ses, struct smb_vol *volume_info) 
	return NULL;

}



static void

void

cifs_put_tcon(struct cifs_tcon *tcon)

{

	unsigned int xid;
@@ -3824,7 +3844,7 @@ cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *volume_info) 
		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);

	}
@@ -4135,7 +4155,7 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid) 
	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;

	}

fs/cifs/smb2pdu.c

+51 −24
Original line number Diff line number Diff line
@@ -1972,6 +1972,54 @@ smb2_echo_callback(struct mid_q_entry *mid) 
	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)

{
@@ -1984,32 +2032,11 @@ 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;

fs/cifs/smb2proto.h

+1 −0
Original line number Diff line number Diff line
@@ -96,6 +96,7 @@ extern int smb2_open_file(const unsigned int xid, 
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