[v3,1/3] CIFS: make IPC a regular tcon

Message ID 20180124124612.21993-2-aaptel@suse.com
State New
Headers show
Series
  • Make IPC a regular tcon and fix SMB2 domain-based DFS
Related show

Commit Message

Aurélien Aptel Jan. 24, 2018, 12:46 p.m.
* Remove ses->ipc_tid.
* Make IPC$ regular tcon.
* Add a direct pointer to it in ses->tcon_ipc.
* Distinguish PIPE tcon from IPC tcon by adding a tcon->pipe flag. All
  IPC tcons are pipes but not all pipes are IPC.
* All TreeConnect functions now cannot take a NULL tcon object.

The IPC tcon has the same lifetime as the session it belongs to. It is
created when the session is created and destroyed when the session is
destroyed.

Since no mounts directly refer to the IPC tcon, its refcount should
always be set to initialisation value (1). Thus we make sure
cifs_put_tcon() skips it.

If the mount request resulting in a new session being created requires
encryption, try to require it too for IPC.

* set SERVER_NAME_LENGTH to serverName actual size

The maximum length of an ipv6 string representation is defined in
INET6_ADDRSTRLEN as 45+1 for null but lets keep what we know works.

Signed-off-by: Aurelien Aptel <aaptel@suse.com>
---
 fs/cifs/cifsglob.h |  14 ++---
 fs/cifs/cifssmb.c  |   7 +--
 fs/cifs/connect.c  | 150 ++++++++++++++++++++++++++++++++++++++++-------------
 fs/cifs/inode.c    |   2 +-
 fs/cifs/smb2pdu.c  |  36 +++----------
 5 files changed, 133 insertions(+), 76 deletions(-)

Comments

Pavel Shilovskiy Jan. 26, 2018, 10:57 p.m. | #1
2018-01-24 4:46 GMT-08:00 Aurelien Aptel <aaptel@suse.com>:
> * Remove ses->ipc_tid.
> * Make IPC$ regular tcon.
> * Add a direct pointer to it in ses->tcon_ipc.
> * Distinguish PIPE tcon from IPC tcon by adding a tcon->pipe flag. All
>   IPC tcons are pipes but not all pipes are IPC.
> * All TreeConnect functions now cannot take a NULL tcon object.
>
> The IPC tcon has the same lifetime as the session it belongs to. It is
> created when the session is created and destroyed when the session is
> destroyed.
>
> Since no mounts directly refer to the IPC tcon, its refcount should
> always be set to initialisation value (1). Thus we make sure
> cifs_put_tcon() skips it.
>
> If the mount request resulting in a new session being created requires
> encryption, try to require it too for IPC.
>
> * set SERVER_NAME_LENGTH to serverName actual size
>
> The maximum length of an ipv6 string representation is defined in
> INET6_ADDRSTRLEN as 45+1 for null but lets keep what we know works.
>
> Signed-off-by: Aurelien Aptel <aaptel@suse.com>
> ---
>  fs/cifs/cifsglob.h |  14 ++---
>  fs/cifs/cifssmb.c  |   7 +--
>  fs/cifs/connect.c  | 150 ++++++++++++++++++++++++++++++++++++++++-------------
>  fs/cifs/inode.c    |   2 +-
>  fs/cifs/smb2pdu.c  |  36 +++----------
>  5 files changed, 133 insertions(+), 76 deletions(-)
>
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index 678e638c1e69..48f7c197cd2d 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -64,8 +64,8 @@
>  #define RFC1001_NAME_LEN 15
>  #define RFC1001_NAME_LEN_WITH_NULL (RFC1001_NAME_LEN + 1)
>
> -/* currently length of NIP6_FMT */
> -#define SERVER_NAME_LENGTH 40
> +/* maximum length of ip addr as a string (including ipv6 and sctp) */
> +#define SERVER_NAME_LENGTH 80
>  #define SERVER_NAME_LEN_WITH_NULL     (SERVER_NAME_LENGTH + 1)
>
>  /* echo interval in seconds */
> @@ -833,12 +833,12 @@ static inline void cifs_set_net_ns(struct TCP_Server_Info *srv, struct net *net)
>  struct cifs_ses {
>         struct list_head smb_ses_list;
>         struct list_head tcon_list;
> +       struct cifs_tcon *tcon_ipc;
>         struct mutex session_mutex;
>         struct TCP_Server_Info *server; /* pointer to server info */
>         int ses_count;          /* reference counter */
>         enum statusEnum status;
>         unsigned overrideSecFlg;  /* if non-zero override global sec flags */
> -       __u32 ipc_tid;          /* special tid for connection to IPC share */
>         char *serverOS;         /* name of operating system underlying server */
>         char *serverNOS;        /* name of network operating system of server */
>         char *serverDomain;     /* security realm of server */
> @@ -846,8 +846,7 @@ struct cifs_ses {
>         kuid_t linux_uid;       /* overriding owner of files on the mount */
>         kuid_t cred_uid;        /* owner of credentials */
>         unsigned int capabilities;
> -       char serverName[SERVER_NAME_LEN_WITH_NULL * 2]; /* BB make bigger for
> -                               TCP names - will ipv6 and sctp addresses fit? */
> +       char serverName[SERVER_NAME_LEN_WITH_NULL];
>         char *user_name;        /* must not be null except during init of sess
>                                    and after mount option parsing we fill it */
>         char *domainName;
> @@ -942,7 +941,9 @@ struct cifs_tcon {
>         FILE_SYSTEM_DEVICE_INFO fsDevInfo;
>         FILE_SYSTEM_ATTRIBUTE_INFO fsAttrInfo; /* ok if fs name truncated */
>         FILE_SYSTEM_UNIX_INFO fsUnixInfo;
> -       bool ipc:1;             /* set if connection to IPC$ eg for RPC/PIPES */
> +       bool ipc:1;   /* set if connection to IPC$ share (always also pipe) */
> +       bool pipe:1;  /* set if connection to pipe share */
> +       bool print:1; /* set if connection to printer share */
>         bool retry:1;
>         bool nocase:1;
>         bool seal:1;      /* transport encryption for this mounted share */
> @@ -955,7 +956,6 @@ struct cifs_tcon {
>         bool need_reopen_files:1; /* need to reopen tcon file handles */
>         bool use_resilient:1; /* use resilient instead of durable handles */
>         bool use_persistent:1; /* use persistent instead of durable handles */
> -       bool print:1;           /* set if connection to printer share */
>         __le32 capabilities;
>         __u32 share_flags;
>         __u32 maximal_access;
> diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
> index 49cf999f3d46..4e0922d24eb2 100644
> --- a/fs/cifs/cifssmb.c
> +++ b/fs/cifs/cifssmb.c
> @@ -4833,10 +4833,11 @@ CIFSGetDFSRefer(const unsigned int xid, struct cifs_ses *ses,
>         *target_nodes = NULL;
>
>         cifs_dbg(FYI, "In GetDFSRefer the path %s\n", search_name);
> -       if (ses == NULL)
> +       if (ses == NULL || ses->tcon_ipc == NULL)
>                 return -ENODEV;
> +
>  getDFSRetry:
> -       rc = smb_init(SMB_COM_TRANSACTION2, 15, NULL, (void **) &pSMB,
> +       rc = smb_init(SMB_COM_TRANSACTION2, 15, ses->tcon_ipc, (void **) &pSMB,
>                       (void **) &pSMBr);
>         if (rc)
>                 return rc;
> @@ -4844,7 +4845,7 @@ CIFSGetDFSRefer(const unsigned int xid, struct cifs_ses *ses,
>         /* server pointer checked in called function,
>         but should never be null here anyway */
>         pSMB->hdr.Mid = get_next_mid(ses->server);
> -       pSMB->hdr.Tid = ses->ipc_tid;
> +       pSMB->hdr.Tid = ses->tcon_ipc->tid;
>         pSMB->hdr.Uid = ses->Suid;
>         if (ses->capabilities & CAP_STATUS32)
>                 pSMB->hdr.Flags2 |= SMBFLG2_ERR_STATUS;
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index 63c5d85fe25e..8b5e401f547a 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -354,11 +354,12 @@ cifs_reconnect(struct TCP_Server_Info *server)
>         list_for_each(tmp, &server->smb_ses_list) {
>                 ses = list_entry(tmp, struct cifs_ses, smb_ses_list);
>                 ses->need_reconnect = true;
> -               ses->ipc_tid = 0;
>                 list_for_each(tmp2, &ses->tcon_list) {
>                         tcon = list_entry(tmp2, struct cifs_tcon, tcon_list);
>                         tcon->need_reconnect = true;
>                 }
> +               if (ses->tcon_ipc)
> +                       ses->tcon_ipc->need_reconnect = true;
>         }
>         spin_unlock(&cifs_tcp_ses_lock);
>
> @@ -2426,6 +2427,93 @@ static int match_session(struct cifs_ses *ses, struct smb_vol *vol)
>         return 1;
>  }
>
> +/**
> + * cifs_setup_ipc - helper to setup the IPC tcon for the session
> + *
> + * A new IPC connection is made and stored in the session
> + * tcon_ipc. The IPC tcon has the same lifetime as the session.
> + */
> +static int
> +cifs_setup_ipc(struct cifs_ses *ses, struct smb_vol *volume_info)
> +{
> +       int rc = 0, xid;
> +       struct cifs_tcon *tcon;
> +       struct nls_table *nls_codepage;
> +       char unc[SERVER_NAME_LENGTH + sizeof("//x/IPC$")] = {0};
> +       bool seal = false;
> +
> +       /*
> +        * If the mount request that resulted in the creation of the
> +        * session requires encryption, force IPC to be encrypted too.
> +        */
> +       if (volume_info->seal) {
> +               if (ses->server->capabilities & SMB2_GLOBAL_CAP_ENCRYPTION)
> +                       seal = true;
> +               else {
> +                       cifs_dbg(VFS,
> +                                "IPC: server doesn't support encryption\n");
> +                       return -EOPNOTSUPP;
> +               }
> +       }
> +
> +       tcon = tconInfoAlloc();
> +       if (tcon == NULL)
> +               return -ENOMEM;
> +
> +       snprintf(unc, sizeof(unc), "\\\\%s\\IPC$", ses->serverName);
> +
> +       /* cannot fail */
> +       nls_codepage = load_nls_default();
> +
> +       xid = get_xid();
> +       tcon->ses = ses;
> +       tcon->ipc = true;
> +       tcon->seal = seal;
> +       rc = ses->server->ops->tree_connect(xid, ses, unc, tcon, nls_codepage);
> +       free_xid(xid);
> +
> +       if (rc) {
> +               cifs_dbg(VFS, "failed to connect to IPC (rc=%d)\n", rc);
> +               tconInfoFree(tcon);
> +               goto out;
> +       }
> +
> +       cifs_dbg(FYI, "IPC tcon rc = %d ipc tid = %d\n", rc, tcon->tid);
> +
> +       ses->tcon_ipc = tcon;
> +out:
> +       unload_nls(nls_codepage);
> +       return rc;
> +}
> +
> +/**
> + * cifs_free_ipc - helper to release the session IPC tcon
> + *
> + * Needs to be called everytime a session is destroyed
> + */
> +static int
> +cifs_free_ipc(struct cifs_ses *ses)
> +{
> +       int rc = 0, xid;
> +       struct cifs_tcon *tcon = ses->tcon_ipc;
> +
> +       if (tcon == NULL)
> +               return 0;
> +
> +       if (ses->server->ops->tree_disconnect) {
> +               xid = get_xid();
> +               rc = ses->server->ops->tree_disconnect(xid, tcon);
> +               free_xid(xid);
> +       }
> +
> +       if (rc)
> +               cifs_dbg(FYI, "failed to disconnect IPC tcon (rc=%d)\n", rc);
> +
> +       tconInfoFree(tcon);
> +       ses->tcon_ipc = NULL;
> +       return rc;
> +}
> +
>  static struct cifs_ses *
>  cifs_find_smb_ses(struct TCP_Server_Info *server, struct smb_vol *vol)
>  {
> @@ -2466,6 +2554,8 @@ cifs_put_smb_ses(struct cifs_ses *ses)
>                 ses->status = CifsExiting;
>         spin_unlock(&cifs_tcp_ses_lock);
>
> +       cifs_free_ipc(ses);
> +
>         if (ses->status == CifsExiting && server->ops->logoff) {
>                 xid = get_xid();
>                 rc = server->ops->logoff(xid, ses);
> @@ -2710,6 +2800,9 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb_vol *volume_info)
>         spin_unlock(&cifs_tcp_ses_lock);
>
>         free_xid(xid);
> +
> +       cifs_setup_ipc(ses, volume_info);
> +
>         return ses;
>
>  get_ses_fail:
> @@ -2754,8 +2847,16 @@ void
>  cifs_put_tcon(struct cifs_tcon *tcon)
>  {
>         unsigned int xid;
> -       struct cifs_ses *ses = tcon->ses;
> +       struct cifs_ses *ses;
>
> +       /*
> +        * IPC tcon share the lifetime of their session and are
> +        * destroyed in the session put function
> +        */
> +       if (tcon == NULL || tcon->ipc)
> +               return;
> +
> +       ses = tcon->ses;
>         cifs_dbg(FYI, "%s: tc_count=%d\n", __func__, tcon->tc_count);
>         spin_lock(&cifs_tcp_ses_lock);
>         if (--tcon->tc_count > 0) {
> @@ -3031,39 +3132,17 @@ get_dfs_path(const unsigned int xid, struct cifs_ses *ses, const char *old_path,
>              const struct nls_table *nls_codepage, unsigned int *num_referrals,
>              struct dfs_info3_param **referrals, int remap)
>  {
> -       char *temp_unc;
>         int rc = 0;
>
> -       if (!ses->server->ops->tree_connect || !ses->server->ops->get_dfs_refer)
> +       if (!ses->server->ops->get_dfs_refer)
>                 return -ENOSYS;
>
>         *num_referrals = 0;
>         *referrals = NULL;
>
> -       if (ses->ipc_tid == 0) {
> -               temp_unc = kmalloc(2 /* for slashes */ +
> -                       strnlen(ses->serverName, SERVER_NAME_LEN_WITH_NULL * 2)
> -                               + 1 + 4 /* slash IPC$ */ + 2, GFP_KERNEL);
> -               if (temp_unc == NULL)
> -                       return -ENOMEM;
> -               temp_unc[0] = '\\';
> -               temp_unc[1] = '\\';
> -               strcpy(temp_unc + 2, ses->serverName);
> -               strcpy(temp_unc + 2 + strlen(ses->serverName), "\\IPC$");
> -               rc = ses->server->ops->tree_connect(xid, ses, temp_unc, NULL,
> -                                                   nls_codepage);
> -               cifs_dbg(FYI, "Tcon rc = %d ipc_tid = %d\n", rc, ses->ipc_tid);
> -               kfree(temp_unc);
> -       }
> -       if (rc == 0)
> -               rc = ses->server->ops->get_dfs_refer(xid, ses, old_path,
> -                                                    referrals, num_referrals,
> -                                                    nls_codepage, remap);
> -       /*
> -        * BB - map targetUNCs to dfs_info3 structures, here or in
> -        * ses->server->ops->get_dfs_refer.
> -        */
> -
> +       rc = ses->server->ops->get_dfs_refer(xid, ses, old_path,
> +                                            referrals, num_referrals,
> +                                            nls_codepage, remap);
>         return rc;
>  }
>
> @@ -3828,7 +3907,7 @@ cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *volume_info)
>                 tcon->unix_ext = 0; /* server does not support them */
>
>         /* do not care if a following call succeed - informational */
> -       if (!tcon->ipc && server->ops->qfs_tcon)
> +       if (!tcon->pipe && server->ops->qfs_tcon)
>                 server->ops->qfs_tcon(xid, tcon);
>
>         cifs_sb->wsize = server->ops->negotiate_wsize(tcon, volume_info);
> @@ -3958,8 +4037,7 @@ cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *volume_info)
>  }
>
>  /*
> - * Issue a TREE_CONNECT request. Note that for IPC$ shares, that the tcon
> - * pointer may be NULL.
> + * Issue a TREE_CONNECT request.
>   */
>  int
>  CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
> @@ -3995,7 +4073,7 @@ CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
>         pSMB->AndXCommand = 0xFF;
>         pSMB->Flags = cpu_to_le16(TCON_EXTENDED_SECINFO);
>         bcc_ptr = &pSMB->Password[0];
> -       if (!tcon || (ses->server->sec_mode & SECMODE_USER)) {
> +       if (tcon->pipe || (ses->server->sec_mode & SECMODE_USER)) {
>                 pSMB->PasswordLength = cpu_to_le16(1);  /* minimum */
>                 *bcc_ptr = 0; /* password is null byte */
>                 bcc_ptr++;              /* skip password */
> @@ -4067,7 +4145,7 @@ CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
>                          0);
>
>         /* above now done in SendReceive */
> -       if ((rc == 0) && (tcon != NULL)) {
> +       if (rc == 0) {
>                 bool is_unicode;
>
>                 tcon->tidStatus = CifsGood;
> @@ -4087,7 +4165,8 @@ CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
>                         if ((bcc_ptr[0] == 'I') && (bcc_ptr[1] == 'P') &&
>                             (bcc_ptr[2] == 'C')) {
>                                 cifs_dbg(FYI, "IPC connection\n");
> -                               tcon->ipc = 1;
> +                               tcon->ipc = true;
> +                               tcon->pipe = true;
>                         }
>                 } else if (length == 2) {
>                         if ((bcc_ptr[0] == 'A') && (bcc_ptr[1] == ':')) {
> @@ -4114,9 +4193,6 @@ CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
>                 else
>                         tcon->Flags = 0;
>                 cifs_dbg(FYI, "Tcon flags: 0x%x\n", tcon->Flags);
> -       } else if ((rc == 0) && tcon == NULL) {
> -               /* all we need to save for IPC$ connection */
> -               ses->ipc_tid = smb_buffer_response->Tid;
>         }
>
>         cifs_buf_release(smb_buffer);
> diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
> index ecb99079363a..8f9a8cc7cc62 100644
> --- a/fs/cifs/inode.c
> +++ b/fs/cifs/inode.c
> @@ -1049,7 +1049,7 @@ struct inode *cifs_root_iget(struct super_block *sb)
>         tcon->resource_id = CIFS_I(inode)->uniqueid;
>  #endif
>
> -       if (rc && tcon->ipc) {
> +       if (rc && tcon->pipe) {
>                 cifs_dbg(FYI, "ipc connection - fake read inode\n");
>                 spin_lock(&inode->i_lock);
>                 inode->i_mode |= S_IFDIR;
> diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
> index 7900aec7f92f..2943adc754e4 100644
> --- a/fs/cifs/smb2pdu.c
> +++ b/fs/cifs/smb2pdu.c
> @@ -1258,8 +1258,7 @@ SMB2_tcon(const unsigned int xid, struct cifs_ses *ses, const char *tree,
>         }
>
>         /* SMB2 TREE_CONNECT request must be called with TreeId == 0 */
> -       if (tcon)
> -               tcon->tid = 0;
> +       tcon->tid = 0;
>
>         rc = smb2_plain_req_init(SMB2_TREE_CONNECT, tcon, (void **) &req,
>                              &total_len);
> @@ -1268,15 +1267,7 @@ SMB2_tcon(const unsigned int xid, struct cifs_ses *ses, const char *tree,
>                 return rc;
>         }
>
> -       if (tcon == NULL) {
> -               if ((ses->session_flags & SMB2_SESSION_FLAG_ENCRYPT_DATA))
> -                       flags |= CIFS_TRANSFORM_REQ;
> -
> -               /* since no tcon, smb2_init can not do this, so do here */
> -               req->sync_hdr.SessionId = ses->Suid;
> -               if (ses->server->sign)
> -                       req->sync_hdr.Flags |= SMB2_FLAGS_SIGNED;
> -       } else if (encryption_required(tcon))
> +       if (encryption_required(tcon))
>                 flags |= CIFS_TRANSFORM_REQ;
>
>         iov[0].iov_base = (char *)req;
> @@ -1302,21 +1293,16 @@ SMB2_tcon(const unsigned int xid, struct cifs_ses *ses, const char *tree,
>                 goto tcon_error_exit;
>         }
>
> -       if (tcon == NULL) {
> -               ses->ipc_tid = rsp->hdr.sync_hdr.TreeId;
> -               goto tcon_exit;
> -       }
> -
>         switch (rsp->ShareType) {
>         case SMB2_SHARE_TYPE_DISK:
>                 cifs_dbg(FYI, "connection to disk share\n");
>                 break;
>         case SMB2_SHARE_TYPE_PIPE:
> -               tcon->ipc = true;
> +               tcon->pipe = true;
>                 cifs_dbg(FYI, "connection to pipe share\n");
>                 break;
>         case SMB2_SHARE_TYPE_PRINT:
> -               tcon->ipc = true;
> +               tcon->print = true;
>                 cifs_dbg(FYI, "connection to printer\n");
>                 break;
>         default:
> @@ -1892,16 +1878,6 @@ SMB2_ioctl(const unsigned int xid, struct cifs_tcon *tcon, u64 persistent_fid,
>         if (rc)
>                 return rc;
>
> -       if (use_ipc) {
> -               if (ses->ipc_tid == 0) {
> -                       cifs_small_buf_release(req);
> -                       return -ENOTCONN;
> -               }
> -
> -               cifs_dbg(FYI, "replacing tid 0x%x with IPC tid 0x%x\n",
> -                        req->sync_hdr.TreeId, ses->ipc_tid);
> -               req->sync_hdr.TreeId = ses->ipc_tid;
> -       }
>         if (encryption_required(tcon))
>                 flags |= CIFS_TRANSFORM_REQ;
>
> @@ -2317,6 +2293,10 @@ void smb2_reconnect_server(struct work_struct *work)
>                                 tcon_exist = true;
>                         }
>                 }
> +               if (ses->tcon_ipc && ses->tcon_ipc->need_reconnect) {
> +                       list_add_tail(&ses->tcon_ipc->rlist, &tmp_list);
> +                       tcon_exist = true;
> +               }
>         }
>         /*
>          * Get the reference to server struct to be sure that the last call of
> --
> 2.12.3
>
> --
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Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>

--
Best regards,
Pavel Shilovsky

--
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Patch

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 678e638c1e69..48f7c197cd2d 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -64,8 +64,8 @@ 
 #define RFC1001_NAME_LEN 15
 #define RFC1001_NAME_LEN_WITH_NULL (RFC1001_NAME_LEN + 1)
 
-/* currently length of NIP6_FMT */
-#define SERVER_NAME_LENGTH 40
+/* maximum length of ip addr as a string (including ipv6 and sctp) */
+#define SERVER_NAME_LENGTH 80
 #define SERVER_NAME_LEN_WITH_NULL     (SERVER_NAME_LENGTH + 1)
 
 /* echo interval in seconds */
@@ -833,12 +833,12 @@  static inline void cifs_set_net_ns(struct TCP_Server_Info *srv, struct net *net)
 struct cifs_ses {
 	struct list_head smb_ses_list;
 	struct list_head tcon_list;
+	struct cifs_tcon *tcon_ipc;
 	struct mutex session_mutex;
 	struct TCP_Server_Info *server;	/* pointer to server info */
 	int ses_count;		/* reference counter */
 	enum statusEnum status;
 	unsigned overrideSecFlg;  /* if non-zero override global sec flags */
-	__u32 ipc_tid;		/* special tid for connection to IPC share */
 	char *serverOS;		/* name of operating system underlying server */
 	char *serverNOS;	/* name of network operating system of server */
 	char *serverDomain;	/* security realm of server */
@@ -846,8 +846,7 @@  struct cifs_ses {
 	kuid_t linux_uid;	/* overriding owner of files on the mount */
 	kuid_t cred_uid;	/* owner of credentials */
 	unsigned int capabilities;
-	char serverName[SERVER_NAME_LEN_WITH_NULL * 2];	/* BB make bigger for
-				TCP names - will ipv6 and sctp addresses fit? */
+	char serverName[SERVER_NAME_LEN_WITH_NULL];
 	char *user_name;	/* must not be null except during init of sess
 				   and after mount option parsing we fill it */
 	char *domainName;
@@ -942,7 +941,9 @@  struct cifs_tcon {
 	FILE_SYSTEM_DEVICE_INFO fsDevInfo;
 	FILE_SYSTEM_ATTRIBUTE_INFO fsAttrInfo; /* ok if fs name truncated */
 	FILE_SYSTEM_UNIX_INFO fsUnixInfo;
-	bool ipc:1;		/* set if connection to IPC$ eg for RPC/PIPES */
+	bool ipc:1;   /* set if connection to IPC$ share (always also pipe) */
+	bool pipe:1;  /* set if connection to pipe share */
+	bool print:1; /* set if connection to printer share */
 	bool retry:1;
 	bool nocase:1;
 	bool seal:1;      /* transport encryption for this mounted share */
@@ -955,7 +956,6 @@  struct cifs_tcon {
 	bool need_reopen_files:1; /* need to reopen tcon file handles */
 	bool use_resilient:1; /* use resilient instead of durable handles */
 	bool use_persistent:1; /* use persistent instead of durable handles */
-	bool print:1;		/* set if connection to printer share */
 	__le32 capabilities;
 	__u32 share_flags;
 	__u32 maximal_access;
diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 49cf999f3d46..4e0922d24eb2 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -4833,10 +4833,11 @@  CIFSGetDFSRefer(const unsigned int xid, struct cifs_ses *ses,
 	*target_nodes = NULL;
 
 	cifs_dbg(FYI, "In GetDFSRefer the path %s\n", search_name);
-	if (ses == NULL)
+	if (ses == NULL || ses->tcon_ipc == NULL)
 		return -ENODEV;
+
 getDFSRetry:
-	rc = smb_init(SMB_COM_TRANSACTION2, 15, NULL, (void **) &pSMB,
+	rc = smb_init(SMB_COM_TRANSACTION2, 15, ses->tcon_ipc, (void **) &pSMB,
 		      (void **) &pSMBr);
 	if (rc)
 		return rc;
@@ -4844,7 +4845,7 @@  CIFSGetDFSRefer(const unsigned int xid, struct cifs_ses *ses,
 	/* server pointer checked in called function,
 	but should never be null here anyway */
 	pSMB->hdr.Mid = get_next_mid(ses->server);
-	pSMB->hdr.Tid = ses->ipc_tid;
+	pSMB->hdr.Tid = ses->tcon_ipc->tid;
 	pSMB->hdr.Uid = ses->Suid;
 	if (ses->capabilities & CAP_STATUS32)
 		pSMB->hdr.Flags2 |= SMBFLG2_ERR_STATUS;
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 63c5d85fe25e..8b5e401f547a 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -354,11 +354,12 @@  cifs_reconnect(struct TCP_Server_Info *server)
 	list_for_each(tmp, &server->smb_ses_list) {
 		ses = list_entry(tmp, struct cifs_ses, smb_ses_list);
 		ses->need_reconnect = true;
-		ses->ipc_tid = 0;
 		list_for_each(tmp2, &ses->tcon_list) {
 			tcon = list_entry(tmp2, struct cifs_tcon, tcon_list);
 			tcon->need_reconnect = true;
 		}
+		if (ses->tcon_ipc)
+			ses->tcon_ipc->need_reconnect = true;
 	}
 	spin_unlock(&cifs_tcp_ses_lock);
 
@@ -2426,6 +2427,93 @@  static int match_session(struct cifs_ses *ses, struct smb_vol *vol)
 	return 1;
 }
 
+/**
+ * cifs_setup_ipc - helper to setup the IPC tcon for the session
+ *
+ * A new IPC connection is made and stored in the session
+ * tcon_ipc. The IPC tcon has the same lifetime as the session.
+ */
+static int
+cifs_setup_ipc(struct cifs_ses *ses, struct smb_vol *volume_info)
+{
+	int rc = 0, xid;
+	struct cifs_tcon *tcon;
+	struct nls_table *nls_codepage;
+	char unc[SERVER_NAME_LENGTH + sizeof("//x/IPC$")] = {0};
+	bool seal = false;
+
+	/*
+	 * If the mount request that resulted in the creation of the
+	 * session requires encryption, force IPC to be encrypted too.
+	 */
+	if (volume_info->seal) {
+		if (ses->server->capabilities & SMB2_GLOBAL_CAP_ENCRYPTION)
+			seal = true;
+		else {
+			cifs_dbg(VFS,
+				 "IPC: server doesn't support encryption\n");
+			return -EOPNOTSUPP;
+		}
+	}
+
+	tcon = tconInfoAlloc();
+	if (tcon == NULL)
+		return -ENOMEM;
+
+	snprintf(unc, sizeof(unc), "\\\\%s\\IPC$", ses->serverName);
+
+	/* cannot fail */
+	nls_codepage = load_nls_default();
+
+	xid = get_xid();
+	tcon->ses = ses;
+	tcon->ipc = true;
+	tcon->seal = seal;
+	rc = ses->server->ops->tree_connect(xid, ses, unc, tcon, nls_codepage);
+	free_xid(xid);
+
+	if (rc) {
+		cifs_dbg(VFS, "failed to connect to IPC (rc=%d)\n", rc);
+		tconInfoFree(tcon);
+		goto out;
+	}
+
+	cifs_dbg(FYI, "IPC tcon rc = %d ipc tid = %d\n", rc, tcon->tid);
+
+	ses->tcon_ipc = tcon;
+out:
+	unload_nls(nls_codepage);
+	return rc;
+}
+
+/**
+ * cifs_free_ipc - helper to release the session IPC tcon
+ *
+ * Needs to be called everytime a session is destroyed
+ */
+static int
+cifs_free_ipc(struct cifs_ses *ses)
+{
+	int rc = 0, xid;
+	struct cifs_tcon *tcon = ses->tcon_ipc;
+
+	if (tcon == NULL)
+		return 0;
+
+	if (ses->server->ops->tree_disconnect) {
+		xid = get_xid();
+		rc = ses->server->ops->tree_disconnect(xid, tcon);
+		free_xid(xid);
+	}
+
+	if (rc)
+		cifs_dbg(FYI, "failed to disconnect IPC tcon (rc=%d)\n", rc);
+
+	tconInfoFree(tcon);
+	ses->tcon_ipc = NULL;
+	return rc;
+}
+
 static struct cifs_ses *
 cifs_find_smb_ses(struct TCP_Server_Info *server, struct smb_vol *vol)
 {
@@ -2466,6 +2554,8 @@  cifs_put_smb_ses(struct cifs_ses *ses)
 		ses->status = CifsExiting;
 	spin_unlock(&cifs_tcp_ses_lock);
 
+	cifs_free_ipc(ses);
+
 	if (ses->status == CifsExiting && server->ops->logoff) {
 		xid = get_xid();
 		rc = server->ops->logoff(xid, ses);
@@ -2710,6 +2800,9 @@  cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb_vol *volume_info)
 	spin_unlock(&cifs_tcp_ses_lock);
 
 	free_xid(xid);
+
+	cifs_setup_ipc(ses, volume_info);
+
 	return ses;
 
 get_ses_fail:
@@ -2754,8 +2847,16 @@  void
 cifs_put_tcon(struct cifs_tcon *tcon)
 {
 	unsigned int xid;
-	struct cifs_ses *ses = tcon->ses;
+	struct cifs_ses *ses;
 
+	/*
+	 * IPC tcon share the lifetime of their session and are
+	 * destroyed in the session put function
+	 */
+	if (tcon == NULL || tcon->ipc)
+		return;
+
+	ses = tcon->ses;
 	cifs_dbg(FYI, "%s: tc_count=%d\n", __func__, tcon->tc_count);
 	spin_lock(&cifs_tcp_ses_lock);
 	if (--tcon->tc_count > 0) {
@@ -3031,39 +3132,17 @@  get_dfs_path(const unsigned int xid, struct cifs_ses *ses, const char *old_path,
 	     const struct nls_table *nls_codepage, unsigned int *num_referrals,
 	     struct dfs_info3_param **referrals, int remap)
 {
-	char *temp_unc;
 	int rc = 0;
 
-	if (!ses->server->ops->tree_connect || !ses->server->ops->get_dfs_refer)
+	if (!ses->server->ops->get_dfs_refer)
 		return -ENOSYS;
 
 	*num_referrals = 0;
 	*referrals = NULL;
 
-	if (ses->ipc_tid == 0) {
-		temp_unc = kmalloc(2 /* for slashes */ +
-			strnlen(ses->serverName, SERVER_NAME_LEN_WITH_NULL * 2)
-				+ 1 + 4 /* slash IPC$ */ + 2, GFP_KERNEL);
-		if (temp_unc == NULL)
-			return -ENOMEM;
-		temp_unc[0] = '\\';
-		temp_unc[1] = '\\';
-		strcpy(temp_unc + 2, ses->serverName);
-		strcpy(temp_unc + 2 + strlen(ses->serverName), "\\IPC$");
-		rc = ses->server->ops->tree_connect(xid, ses, temp_unc, NULL,
-						    nls_codepage);
-		cifs_dbg(FYI, "Tcon rc = %d ipc_tid = %d\n", rc, ses->ipc_tid);
-		kfree(temp_unc);
-	}
-	if (rc == 0)
-		rc = ses->server->ops->get_dfs_refer(xid, ses, old_path,
-						     referrals, num_referrals,
-						     nls_codepage, remap);
-	/*
-	 * BB - map targetUNCs to dfs_info3 structures, here or in
-	 * ses->server->ops->get_dfs_refer.
-	 */
-
+	rc = ses->server->ops->get_dfs_refer(xid, ses, old_path,
+					     referrals, num_referrals,
+					     nls_codepage, remap);
 	return rc;
 }
 
@@ -3828,7 +3907,7 @@  cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *volume_info)
 		tcon->unix_ext = 0; /* server does not support them */
 
 	/* do not care if a following call succeed - informational */
-	if (!tcon->ipc && server->ops->qfs_tcon)
+	if (!tcon->pipe && server->ops->qfs_tcon)
 		server->ops->qfs_tcon(xid, tcon);
 
 	cifs_sb->wsize = server->ops->negotiate_wsize(tcon, volume_info);
@@ -3958,8 +4037,7 @@  cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *volume_info)
 }
 
 /*
- * Issue a TREE_CONNECT request. Note that for IPC$ shares, that the tcon
- * pointer may be NULL.
+ * Issue a TREE_CONNECT request.
  */
 int
 CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
@@ -3995,7 +4073,7 @@  CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
 	pSMB->AndXCommand = 0xFF;
 	pSMB->Flags = cpu_to_le16(TCON_EXTENDED_SECINFO);
 	bcc_ptr = &pSMB->Password[0];
-	if (!tcon || (ses->server->sec_mode & SECMODE_USER)) {
+	if (tcon->pipe || (ses->server->sec_mode & SECMODE_USER)) {
 		pSMB->PasswordLength = cpu_to_le16(1);	/* minimum */
 		*bcc_ptr = 0; /* password is null byte */
 		bcc_ptr++;              /* skip password */
@@ -4067,7 +4145,7 @@  CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
 			 0);
 
 	/* above now done in SendReceive */
-	if ((rc == 0) && (tcon != NULL)) {
+	if (rc == 0) {
 		bool is_unicode;
 
 		tcon->tidStatus = CifsGood;
@@ -4087,7 +4165,8 @@  CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
 			if ((bcc_ptr[0] == 'I') && (bcc_ptr[1] == 'P') &&
 			    (bcc_ptr[2] == 'C')) {
 				cifs_dbg(FYI, "IPC connection\n");
-				tcon->ipc = 1;
+				tcon->ipc = true;
+				tcon->pipe = true;
 			}
 		} else if (length == 2) {
 			if ((bcc_ptr[0] == 'A') && (bcc_ptr[1] == ':')) {
@@ -4114,9 +4193,6 @@  CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
 		else
 			tcon->Flags = 0;
 		cifs_dbg(FYI, "Tcon flags: 0x%x\n", tcon->Flags);
-	} else if ((rc == 0) && tcon == NULL) {
-		/* all we need to save for IPC$ connection */
-		ses->ipc_tid = smb_buffer_response->Tid;
 	}
 
 	cifs_buf_release(smb_buffer);
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index ecb99079363a..8f9a8cc7cc62 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -1049,7 +1049,7 @@  struct inode *cifs_root_iget(struct super_block *sb)
 	tcon->resource_id = CIFS_I(inode)->uniqueid;
 #endif
 
-	if (rc && tcon->ipc) {
+	if (rc && tcon->pipe) {
 		cifs_dbg(FYI, "ipc connection - fake read inode\n");
 		spin_lock(&inode->i_lock);
 		inode->i_mode |= S_IFDIR;
diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 7900aec7f92f..2943adc754e4 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -1258,8 +1258,7 @@  SMB2_tcon(const unsigned int xid, struct cifs_ses *ses, const char *tree,
 	}
 
 	/* SMB2 TREE_CONNECT request must be called with TreeId == 0 */
-	if (tcon)
-		tcon->tid = 0;
+	tcon->tid = 0;
 
 	rc = smb2_plain_req_init(SMB2_TREE_CONNECT, tcon, (void **) &req,
 			     &total_len);
@@ -1268,15 +1267,7 @@  SMB2_tcon(const unsigned int xid, struct cifs_ses *ses, const char *tree,
 		return rc;
 	}
 
-	if (tcon == NULL) {
-		if ((ses->session_flags & SMB2_SESSION_FLAG_ENCRYPT_DATA))
-			flags |= CIFS_TRANSFORM_REQ;
-
-		/* since no tcon, smb2_init can not do this, so do here */
-		req->sync_hdr.SessionId = ses->Suid;
-		if (ses->server->sign)
-			req->sync_hdr.Flags |= SMB2_FLAGS_SIGNED;
-	} else if (encryption_required(tcon))
+	if (encryption_required(tcon))
 		flags |= CIFS_TRANSFORM_REQ;
 
 	iov[0].iov_base = (char *)req;
@@ -1302,21 +1293,16 @@  SMB2_tcon(const unsigned int xid, struct cifs_ses *ses, const char *tree,
 		goto tcon_error_exit;
 	}
 
-	if (tcon == NULL) {
-		ses->ipc_tid = rsp->hdr.sync_hdr.TreeId;
-		goto tcon_exit;
-	}
-
 	switch (rsp->ShareType) {
 	case SMB2_SHARE_TYPE_DISK:
 		cifs_dbg(FYI, "connection to disk share\n");
 		break;
 	case SMB2_SHARE_TYPE_PIPE:
-		tcon->ipc = true;
+		tcon->pipe = true;
 		cifs_dbg(FYI, "connection to pipe share\n");
 		break;
 	case SMB2_SHARE_TYPE_PRINT:
-		tcon->ipc = true;
+		tcon->print = true;
 		cifs_dbg(FYI, "connection to printer\n");
 		break;
 	default:
@@ -1892,16 +1878,6 @@  SMB2_ioctl(const unsigned int xid, struct cifs_tcon *tcon, u64 persistent_fid,
 	if (rc)
 		return rc;
 
-	if (use_ipc) {
-		if (ses->ipc_tid == 0) {
-			cifs_small_buf_release(req);
-			return -ENOTCONN;
-		}
-
-		cifs_dbg(FYI, "replacing tid 0x%x with IPC tid 0x%x\n",
-			 req->sync_hdr.TreeId, ses->ipc_tid);
-		req->sync_hdr.TreeId = ses->ipc_tid;
-	}
 	if (encryption_required(tcon))
 		flags |= CIFS_TRANSFORM_REQ;
 
@@ -2317,6 +2293,10 @@  void smb2_reconnect_server(struct work_struct *work)
 				tcon_exist = true;
 			}
 		}
+		if (ses->tcon_ipc && ses->tcon_ipc->need_reconnect) {
+			list_add_tail(&ses->tcon_ipc->rlist, &tmp_list);
+			tcon_exist = true;
+		}
 	}
 	/*
 	 * Get the reference to server struct to be sure that the last call of