CIFS: Implement follow_link for SMB2

that allows to access files through symlink created on a server.

Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Pavel Shilovsky <pshilovsky@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>

11 files changed, 103 insertions, 29 deletions

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 52ca861ed35e..ec6c3fbb29eb 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -308,6 +308,9 @@ struct smb_version_operations {
         int (*create_hardlink)(const unsigned int, struct cifs_tcon *,
                                const char *, const char *,
                                struct cifs_sb_info *);
+        /* query symlink target */
+        int (*query_symlink)(const unsigned int, struct cifs_tcon *,
+                             const char *, char **, struct cifs_sb_info *);
         /* open a file for non-posix mounts */
         int (*open)(const unsigned int, struct cifs_open_parms *,
                     __u32 *, FILE_ALL_INFO *);
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index 449b6cf09b09..ec0f3423cdac 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -549,6 +549,10 @@ cifs_all_info_to_fattr(struct cifs_fattr *fattr, FILE_ALL_INFO *info,
                  * when Unix extensions are disabled - fake it.
                  */
                 fattr->cf_nlink = 2;
+        } else if (fattr->cf_cifsattrs & ATTR_REPARSE) {
+                fattr->cf_mode = S_IFLNK;
+                fattr->cf_dtype = DT_LNK;
+                fattr->cf_nlink = le32_to_cpu(info->NumberOfLinks);
         } else {
                 fattr->cf_mode = S_IFREG | cifs_sb->mnt_file_mode;
                 fattr->cf_dtype = DT_REG;
diff --git a/fs/cifs/link.c b/fs/cifs/link.c
index 562044f700e5..7e36ceba0c7a 100644
--- a/fs/cifs/link.c
+++ b/fs/cifs/link.c
@@ -509,6 +509,7 @@ cifs_follow_link(struct dentry *direntry, struct nameidata *nd)
         struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
         struct tcon_link *tlink = NULL;
         struct cifs_tcon *tcon;
+        struct TCP_Server_Info *server;
 
         xid = get_xid();
 
@@ -519,25 +520,7 @@ cifs_follow_link(struct dentry *direntry, struct nameidata *nd)
                 goto out;
         }
         tcon = tlink_tcon(tlink);
-
-        /*
-         * For now, we just handle symlinks with unix extensions enabled.
-         * Eventually we should handle NTFS reparse points, and MacOS
-         * symlink support. For instance...
-         *
-         * rc = CIFSSMBQueryReparseLinkInfo(...)
-         *
-         * For now, just return -EACCES when the server doesn't support posix
-         * extensions. Note that we still allow querying symlinks when posix
-         * extensions are manually disabled. We could disable these as well
-         * but there doesn't seem to be any harm in allowing the client to
-         * read them.
-         */
-        if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS) &&
-            !cap_unix(tcon->ses)) {
-                rc = -EACCES;
-                goto out;
-        }
+        server = tcon->ses->server;
 
         full_path = build_path_from_dentry(direntry);
         if (!full_path)
@@ -559,6 +542,9 @@ cifs_follow_link(struct dentry *direntry, struct nameidata *nd)
         if ((rc != 0) && cap_unix(tcon->ses))
                 rc = CIFSSMBUnixQuerySymLink(xid, tcon, full_path, &target_path,
                                              cifs_sb->local_nls);
+        else if (rc != 0 && server->ops->query_symlink)
+                rc = server->ops->query_symlink(xid, tcon, full_path,
+                                                &target_path, cifs_sb);
 
         kfree(full_path);
 out:
diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c
index 69d2c826a23b..42ef03be089f 100644
--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -172,6 +172,9 @@ cifs_fill_common_info(struct cifs_fattr *fattr, struct cifs_sb_info *cifs_sb)
                 if (cifs_dfs_is_possible(cifs_sb) &&
                     (fattr->cf_cifsattrs & ATTR_REPARSE))
                         fattr->cf_flags |= CIFS_FATTR_NEED_REVAL;
+        } else if (fattr->cf_cifsattrs & ATTR_REPARSE) {
+                fattr->cf_mode = S_IFLNK;
+                fattr->cf_dtype = DT_LNK;
         } else {
                 fattr->cf_mode = S_IFREG | cifs_sb->mnt_file_mode;
                 fattr->cf_dtype = DT_REG;
diff --git a/fs/cifs/smb2file.c b/fs/cifs/smb2file.c
index 04a81a4142c3..020245d5c9a7 100644
--- a/fs/cifs/smb2file.c
+++ b/fs/cifs/smb2file.c
@@ -86,7 +86,7 @@ smb2_open_file(const unsigned int xid, struct cifs_open_parms *oparms,
         if (oparms->tcon->ses->server->capabilities & SMB2_GLOBAL_CAP_LEASING)
                 memcpy(smb2_oplock + 1, fid->lease_key, SMB2_LEASE_KEY_SIZE);
 
-        rc = SMB2_open(xid, oparms, smb2_path, smb2_oplock, smb2_data);
+        rc = SMB2_open(xid, oparms, smb2_path, smb2_oplock, smb2_data, NULL);
         if (rc)
                 goto out;
 
diff --git a/fs/cifs/smb2inode.c b/fs/cifs/smb2inode.c
index c6ec1633309a..78ff88c467b9 100644
--- a/fs/cifs/smb2inode.c
+++ b/fs/cifs/smb2inode.c
@@ -60,7 +60,7 @@ smb2_open_op_close(const unsigned int xid, struct cifs_tcon *tcon,
         oparms.fid = &fid;
         oparms.reconnect = false;
 
-        rc = SMB2_open(xid, &oparms, utf16_path, &oplock, NULL);
+        rc = SMB2_open(xid, &oparms, utf16_path, &oplock, NULL, NULL);
         if (rc) {
                 kfree(utf16_path);
                 return rc;
@@ -136,7 +136,8 @@ smb2_query_path_info(const unsigned int xid, struct cifs_tcon *tcon,
                 return -ENOMEM;
 
         rc = smb2_open_op_close(xid, tcon, cifs_sb, full_path,
-                                FILE_READ_ATTRIBUTES, FILE_OPEN, 0, smb2_data,
+                                FILE_READ_ATTRIBUTES, FILE_OPEN,
+                                OPEN_REPARSE_POINT, smb2_data,
                                 SMB2_OP_QUERY_INFO);
         if (rc)
                 goto out;
@@ -191,8 +192,8 @@ smb2_unlink(const unsigned int xid, struct cifs_tcon *tcon, const char *name,
             struct cifs_sb_info *cifs_sb)
 {
         return smb2_open_op_close(xid, tcon, cifs_sb, name, DELETE, FILE_OPEN,
-                                  CREATE_DELETE_ON_CLOSE, NULL,
-                                  SMB2_OP_DELETE);
+                                  CREATE_DELETE_ON_CLOSE | OPEN_REPARSE_POINT,
+                                  NULL, SMB2_OP_DELETE);
 }
 
 static int
diff --git a/fs/cifs/smb2misc.c b/fs/cifs/smb2misc.c
index b0c43345cd98..6103359fb598 100644
--- a/fs/cifs/smb2misc.c
+++ b/fs/cifs/smb2misc.c
@@ -171,6 +171,10 @@ smb2_check_message(char *buf, unsigned int length)
         if (4 + len != clc_len) {
                 cifs_dbg(FYI, "Calculated size %u length %u mismatch mid %llu\n",
                          clc_len, 4 + len, mid);
+                /* create failed on symlink */
+                if (command == SMB2_CREATE_HE &&
+                    hdr->Status == STATUS_STOPPED_ON_SYMLINK)
+                        return 0;
                 /* Windows 7 server returns 24 bytes more */
                 if (clc_len + 20 == len && command == SMB2_OPLOCK_BREAK_HE)
                         return 0;
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index f259e6cc8357..91b9e5422e9a 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -24,6 +24,7 @@
 #include "smb2proto.h"
 #include "cifsproto.h"
 #include "cifs_debug.h"
+#include "cifs_unicode.h"
 #include "smb2status.h"
 #include "smb2glob.h"
 
@@ -229,7 +230,7 @@ smb2_is_path_accessible(const unsigned int xid, struct cifs_tcon *tcon,
         oparms.fid = &fid;
         oparms.reconnect = false;
 
-        rc = SMB2_open(xid, &oparms, utf16_path, &oplock, NULL);
+        rc = SMB2_open(xid, &oparms, utf16_path, &oplock, NULL, NULL);
         if (rc) {
                 kfree(utf16_path);
                 return rc;
@@ -463,7 +464,7 @@ smb2_query_dir_first(const unsigned int xid, struct cifs_tcon *tcon,
         oparms.fid = fid;
         oparms.reconnect = false;
 
-        rc = SMB2_open(xid, &oparms, utf16_path, &oplock, NULL);
+        rc = SMB2_open(xid, &oparms, utf16_path, &oplock, NULL, NULL);
         kfree(utf16_path);
         if (rc) {
                 cifs_dbg(VFS, "open dir failed\n");
@@ -550,7 +551,7 @@ smb2_queryfs(const unsigned int xid, struct cifs_tcon *tcon,
         oparms.fid = &fid;
         oparms.reconnect = false;
 
-        rc = SMB2_open(xid, &oparms, &srch_path, &oplock, NULL);
+        rc = SMB2_open(xid, &oparms, &srch_path, &oplock, NULL, NULL);
         if (rc)
                 return rc;
         buf->f_type = SMB2_MAGIC_NUMBER;
@@ -596,6 +597,57 @@ smb2_new_lease_key(struct cifs_fid *fid)
         get_random_bytes(fid->lease_key, SMB2_LEASE_KEY_SIZE);
 }
 
+static int
+smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
+                   const char *full_path, char **target_path,
+                   struct cifs_sb_info *cifs_sb)
+{
+        int rc;
+        __le16 *utf16_path;
+        __u8 oplock = SMB2_OPLOCK_LEVEL_NONE;
+        struct cifs_open_parms oparms;
+        struct cifs_fid fid;
+        struct smb2_err_rsp *err_buf = NULL;
+        struct smb2_symlink_err_rsp *symlink;
+        unsigned int sub_len, sub_offset;
+
+        cifs_dbg(FYI, "%s: path: %s\n", __func__, full_path);
+
+        utf16_path = cifs_convert_path_to_utf16(full_path, cifs_sb);
+        if (!utf16_path)
+                return -ENOMEM;
+
+        oparms.tcon = tcon;
+        oparms.desired_access = FILE_READ_ATTRIBUTES;
+        oparms.disposition = FILE_OPEN;
+        oparms.create_options = 0;
+        oparms.fid = &fid;
+        oparms.reconnect = false;
+
+        rc = SMB2_open(xid, &oparms, utf16_path, &oplock, NULL, &err_buf);
+
+        if (!rc || !err_buf) {
+                kfree(utf16_path);
+                return -ENOENT;
+        }
+        /* open must fail on symlink - reset rc */
+        rc = 0;
+        symlink = (struct smb2_symlink_err_rsp *)err_buf->ErrorData;
+        sub_len = le16_to_cpu(symlink->SubstituteNameLength);
+        sub_offset = le16_to_cpu(symlink->SubstituteNameOffset);
+        *target_path = cifs_strndup_from_utf16(
+                                (char *)symlink->PathBuffer + sub_offset,
+                                sub_len, true, cifs_sb->local_nls);
+        if (!(*target_path)) {
+                kfree(utf16_path);
+                return -ENOMEM;
+        }
+        convert_delimiter(*target_path, '/');
+        cifs_dbg(FYI, "%s: target path: %s\n", __func__, *target_path);
+        kfree(utf16_path);
+        return rc;
+}
+
 struct smb_version_operations smb21_operations = {
         .compare_fids = smb2_compare_fids,
         .setup_request = smb2_setup_request,
@@ -638,6 +690,7 @@ struct smb_version_operations smb21_operations = {
         .unlink = smb2_unlink,
         .rename = smb2_rename_path,
         .create_hardlink = smb2_create_hardlink,
+        .query_symlink = smb2_query_symlink,
         .open = smb2_open_file,
         .set_fid = smb2_set_fid,
         .close = smb2_close_file,
@@ -706,6 +759,7 @@ struct smb_version_operations smb30_operations = {
         .unlink = smb2_unlink,
         .rename = smb2_rename_path,
         .create_hardlink = smb2_create_hardlink,
+        .query_symlink = smb2_query_symlink,
         .open = smb2_open_file,
         .set_fid = smb2_set_fid,
         .close = smb2_close_file,
diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index abc9c2809b51..5a49861633a6 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -977,7 +977,8 @@ add_durable_context(struct kvec *iov, unsigned int *num_iovec,
 
 int
 SMB2_open(const unsigned int xid, struct cifs_open_parms *oparms, __le16 *path,
-          __u8 *oplock, struct smb2_file_all_info *buf)
+          __u8 *oplock, struct smb2_file_all_info *buf,
+          struct smb2_err_rsp **err_buf)
 {
         struct smb2_create_req *req;
         struct smb2_create_rsp *rsp;
@@ -1082,6 +1083,9 @@ SMB2_open(const unsigned int xid, struct cifs_open_parms *oparms, __le16 *path,
 
         if (rc != 0) {
                 cifs_stats_fail_inc(tcon, SMB2_CREATE_HE);
+                if (err_buf)
+                        *err_buf = kmemdup(rsp, get_rfc1002_length(rsp) + 4,
+                                           GFP_KERNEL);
                 goto creat_exit;
         }
 
diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h
index 36b0d37ea69b..40baeae60b08 100644
--- a/fs/cifs/smb2pdu.h
+++ b/fs/cifs/smb2pdu.h
@@ -150,6 +150,20 @@ struct smb2_err_rsp {
         __u8   ErrorData[1];  /* variable length */
 } __packed;
 
+struct smb2_symlink_err_rsp {
+        __le32 SymLinkLength;
+        __le32 SymLinkErrorTag;
+        __le32 ReparseTag;
+        __le16 ReparseDataLength;
+        __le16 UnparsedPathLength;
+        __le16 SubstituteNameOffset;
+        __le16 SubstituteNameLength;
+        __le16 PrintNameOffset;
+        __le16 PrintNameLength;
+        __le32 Flags;
+        __u8  PathBuffer[0];
+} __packed;
+
 #define SMB2_CLIENT_GUID_SIZE 16
 
 extern __u8 cifs_client_guid[SMB2_CLIENT_GUID_SIZE];
diff --git a/fs/cifs/smb2proto.h b/fs/cifs/smb2proto.h
index 1a5ecbed40ed..1db89fda1392 100644
--- a/fs/cifs/smb2proto.h
+++ b/fs/cifs/smb2proto.h
@@ -106,7 +106,8 @@ extern int SMB2_tcon(const unsigned int xid, struct cifs_ses *ses,
 extern int SMB2_tdis(const unsigned int xid, struct cifs_tcon *tcon);
 extern int SMB2_open(const unsigned int xid, struct cifs_open_parms *oparms,
                      __le16 *path, __u8 *oplock,
-                     struct smb2_file_all_info *buf);
+                     struct smb2_file_all_info *buf,
+                     struct smb2_err_rsp **err_buf);
 extern int SMB2_ioctl(const unsigned int xid, struct cifs_tcon *tcon,
                      u64 persistent_fid, u64 volatile_fid, u32 opcode,
                      bool is_fsctl, char *in_data, u32 indatalen,