cifs: add separate cred_uid field to sesInfo

Right now, there's no clear separation between the uid that owns the
credentials used to do the mount and the overriding owner of the files
on that mount.

Add a separate cred_uid field that is set to the real uid
of the mount user. Unlike the linux_uid, the uid= option does not
override this parameter. The parm is sent to cifs.upcall, which can then
preferentially use the creduid= parm instead of the uid= parm for
finding credentials.

This is not the only way to solve this. We could try to do all of this
in kernel instead by having a module parameter that affects what gets
passed in the uid= field of the upcall. That said, we have a lot more
flexibility to change things in userspace so I think it probably makes
sense to do it this way.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/cifs_spnego.c

@@ -143,6 +143,9 @@ cifs_get_spnego_key(struct cifsSesInfo *sesInfo)
 	dp = description + strlen(description);
 	sprintf(dp, ";uid=0x%x", sesInfo->linux_uid);
 
+	dp = description + strlen(description);
+	sprintf(dp, ";creduid=0x%x", sesInfo->cred_uid);
+
 	dp = description + strlen(description);
 	sprintf(dp, ";user=%s", sesInfo->userName);
 

fs/cifs/cifsglob.h

@@ -214,7 +214,8 @@ struct cifsSesInfo {
 	char *serverNOS;	/* name of network operating system of server */
 	char *serverDomain;	/* security realm of server */
 	int Suid;		/* remote smb uid  */
-	uid_t linux_uid;        /* local Linux uid */
+	uid_t linux_uid;        /* overriding owner of files on the mount */
+	uid_t cred_uid;		/* owner of credentials */
 	int capabilities;
 	char serverName[SERVER_NAME_LEN_WITH_NULL * 2];	/* BB make bigger for
 				TCP names - will ipv6 and sctp addresses fit? */

fs/cifs/connect.c

@@ -67,6 +67,7 @@ struct smb_vol {
 	char *iocharset;  /* local code page for mapping to and from Unicode */
 	char source_rfc1001_name[16]; /* netbios name of client */
 	char target_rfc1001_name[16]; /* netbios name of server for Win9x/ME */
+	uid_t cred_uid;
 	uid_t linux_uid;
 	gid_t linux_gid;
 	mode_t file_mode;
@@ -832,7 +833,8 @@ cifs_parse_mount_options(char *options, const char *devname,
 	/* null target name indicates to use *SMBSERVR default called name
 	   if we end up sending RFC1001 session initialize */
 	vol->target_rfc1001_name[0] = 0;
-	vol->linux_uid = current_uid();  /* use current_euid() instead? */
+	vol->cred_uid = current_uid();
+	vol->linux_uid = current_uid();
 	vol->linux_gid = current_gid();
 
 	/* default to only allowing write access to owner of the mount */
@@ -1658,7 +1660,7 @@ cifs_find_smb_ses(struct TCP_Server_Info *server, struct smb_vol *vol)
 	list_for_each_entry(ses, &server->smb_ses_list, smb_ses_list) {
 		switch (server->secType) {
 		case Kerberos:
-			if (vol->linux_uid != ses->linux_uid)
+			if (vol->cred_uid != ses->cred_uid)
 				continue;
 			break;
 		default:
@@ -1775,6 +1777,7 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb_vol *volume_info)
 		if (ses->domainName)
 			strcpy(ses->domainName, volume_info->domainname);
 	}
+	ses->cred_uid = volume_info->cred_uid;
 	ses->linux_uid = volume_info->linux_uid;
 	ses->overrideSecFlg = volume_info->secFlg;