two fixes for Windows symlink handling

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Merge tag '6.12-rc2-cifs-fixes' of git://git.samba.org/sfrench/cifs-2.6

Pull smb client fixes from Steve French:
 "Two fixes for Windows symlink handling"

* tag '6.12-rc2-cifs-fixes' of git://git.samba.org/sfrench/cifs-2.6:
  cifs: Fix creating native symlinks pointing to current or parent directory
  cifs: Improve creating native symlinks pointing to directory

fs/smb/client/cifs_unicode.c

@@ -484,10 +484,21 @@ cifsConvertToUTF16(__le16 *target, const char *source, int srclen,
 			/**
 			 * Remap spaces and periods found at the end of every
 			 * component of the path. The special cases of '.' and
-			 * '..' do not need to be dealt with explicitly because
-			 * they are addressed in namei.c:link_path_walk().
+			 * '..' are need to be handled because of symlinks.
+			 * They are treated as non-end-of-string to avoid
+			 * remapping and breaking symlinks pointing to . or ..
 			 **/
-			if ((i == srclen - 1) || (source[i+1] == '\\'))
+			if ((i == 0 || source[i-1] == '\\') &&
+			    source[i] == '.' &&
+			    (i == srclen-1 || source[i+1] == '\\'))
+				end_of_string = false; /* "." case */
+			else if (i >= 1 &&
+				 (i == 1 || source[i-2] == '\\') &&
+				 source[i-1] == '.' &&
+				 source[i] == '.' &&
+				 (i == srclen-1 || source[i+1] == '\\'))
+				end_of_string = false; /* ".." case */
+			else if ((i == srclen - 1) || (source[i+1] == '\\'))
 				end_of_string = true;
 			else
 				end_of_string = false;

fs/smb/client/reparse.c

@@ -14,6 +14,12 @@
 #include "fs_context.h"
 #include "reparse.h"
 
+static int detect_directory_symlink_target(struct cifs_sb_info *cifs_sb,
+					   const unsigned int xid,
+					   const char *full_path,
+					   const char *symname,
+					   bool *directory);
+
 int smb2_create_reparse_symlink(const unsigned int xid, struct inode *inode,
 				struct dentry *dentry, struct cifs_tcon *tcon,
 				const char *full_path, const char *symname)
@@ -24,6 +30,7 @@ int smb2_create_reparse_symlink(const unsigned int xid, struct inode *inode,
 	struct inode *new;
 	struct kvec iov;
 	__le16 *path;
+	bool directory;
 	char *sym, sep = CIFS_DIR_SEP(cifs_sb);
 	u16 len, plen;
 	int rc = 0;
@@ -45,6 +52,18 @@ int smb2_create_reparse_symlink(const unsigned int xid, struct inode *inode,
 		goto out;
 	}
 
+	/*
+	 * SMB distinguish between symlink to directory and symlink to file.
+	 * They cannot be exchanged (symlink of file type which points to
+	 * directory cannot be resolved and vice-versa). Try to detect if
+	 * the symlink target could be a directory or not. When detection
+	 * fails then treat symlink as a file (non-directory) symlink.
+	 */
+	directory = false;
+	rc = detect_directory_symlink_target(cifs_sb, xid, full_path, symname, &directory);
+	if (rc < 0)
+		goto out;
+
 	plen = 2 * UniStrnlen((wchar_t *)path, PATH_MAX);
 	len = sizeof(*buf) + plen * 2;
 	buf = kzalloc(len, GFP_KERNEL);
@@ -69,7 +88,8 @@ int smb2_create_reparse_symlink(const unsigned int xid, struct inode *inode,
 	iov.iov_base = buf;
 	iov.iov_len = len;
 	new = smb2_get_reparse_inode(&data, inode->i_sb, xid,
-				     tcon, full_path, &iov, NULL);
+				     tcon, full_path, directory,
+				     &iov, NULL);
 	if (!IS_ERR(new))
 		d_instantiate(dentry, new);
 	else
@@ -81,6 +101,144 @@ out:
 	return rc;
 }
 
+static int detect_directory_symlink_target(struct cifs_sb_info *cifs_sb,
+					   const unsigned int xid,
+					   const char *full_path,
+					   const char *symname,
+					   bool *directory)
+{
+	char sep = CIFS_DIR_SEP(cifs_sb);
+	struct cifs_open_parms oparms;
+	struct tcon_link *tlink;
+	struct cifs_tcon *tcon;
+	const char *basename;
+	struct cifs_fid fid;
+	char *resolved_path;
+	int full_path_len;
+	int basename_len;
+	int symname_len;
+	char *path_sep;
+	__u32 oplock;
+	int open_rc;
+
+	/*
+	 * First do some simple check. If the original Linux symlink target ends
+	 * with slash, or last path component is dot or dot-dot then it is for
+	 * sure symlink to the directory.
+	 */
+	basename = kbasename(symname);
+	basename_len = strlen(basename);
+	if (basename_len == 0 || /* symname ends with slash */
+	    (basename_len == 1 && basename[0] == '.') || /* last component is "." */
+	    (basename_len == 2 && basename[0] == '.' && basename[1] == '.')) { /* or ".." */
+		*directory = true;
+		return 0;
+	}
+
+	/*
+	 * For absolute symlinks it is not possible to determinate
+	 * if it should point to directory or file.
+	 */
+	if (symname[0] == '/') {
+		cifs_dbg(FYI,
+			 "%s: cannot determinate if the symlink target path '%s' "
+			 "is directory or not, creating '%s' as file symlink\n",
+			 __func__, symname, full_path);
+		return 0;
+	}
+
+	/*
+	 * If it was not detected as directory yet and the symlink is relative
+	 * then try to resolve the path on the SMB server, check if the path
+	 * exists and determinate if it is a directory or not.
+	 */
+
+	full_path_len = strlen(full_path);
+	symname_len = strlen(symname);
+
+	tlink = cifs_sb_tlink(cifs_sb);
+	if (IS_ERR(tlink))
+		return PTR_ERR(tlink);
+
+	resolved_path = kzalloc(full_path_len + symname_len + 1, GFP_KERNEL);
+	if (!resolved_path) {
+		cifs_put_tlink(tlink);
+		return -ENOMEM;
+	}
+
+	/*
+	 * Compose the resolved SMB symlink path from the SMB full path
+	 * and Linux target symlink path.
+	 */
+	memcpy(resolved_path, full_path, full_path_len+1);
+	path_sep = strrchr(resolved_path, sep);
+	if (path_sep)
+		path_sep++;
+	else
+		path_sep = resolved_path;
+	memcpy(path_sep, symname, symname_len+1);
+	if (sep == '\\')
+		convert_delimiter(path_sep, sep);
+
+	tcon = tlink_tcon(tlink);
+	oparms = CIFS_OPARMS(cifs_sb, tcon, resolved_path,
+			     FILE_READ_ATTRIBUTES, FILE_OPEN, 0, ACL_NO_MODE);
+	oparms.fid = &fid;
+
+	/* Try to open as a directory (NOT_FILE) */
+	oplock = 0;
+	oparms.create_options = cifs_create_options(cifs_sb,
+						    CREATE_NOT_FILE | OPEN_REPARSE_POINT);
+	open_rc = tcon->ses->server->ops->open(xid, &oparms, &oplock, NULL);
+	if (open_rc == 0) {
+		/* Successful open means that the target path is definitely a directory. */
+		*directory = true;
+		tcon->ses->server->ops->close(xid, tcon, &fid);
+	} else if (open_rc == -ENOTDIR) {
+		/* -ENOTDIR means that the target path is definitely a file. */
+		*directory = false;
+	} else if (open_rc == -ENOENT) {
+		/* -ENOENT means that the target path does not exist. */
+		cifs_dbg(FYI,
+			 "%s: symlink target path '%s' does not exist, "
+			 "creating '%s' as file symlink\n",
+			 __func__, symname, full_path);
+	} else {
+		/* Try to open as a file (NOT_DIR) */
+		oplock = 0;
+		oparms.create_options = cifs_create_options(cifs_sb,
+							    CREATE_NOT_DIR | OPEN_REPARSE_POINT);
+		open_rc = tcon->ses->server->ops->open(xid, &oparms, &oplock, NULL);
+		if (open_rc == 0) {
+			/* Successful open means that the target path is definitely a file. */
+			*directory = false;
+			tcon->ses->server->ops->close(xid, tcon, &fid);
+		} else if (open_rc == -EISDIR) {
+			/* -EISDIR means that the target path is definitely a directory. */
+			*directory = true;
+		} else {
+			/*
+			 * This code branch is called when we do not have a permission to
+			 * open the resolved_path or some other client/process denied
+			 * opening the resolved_path.
+			 *
+			 * TODO: Try to use ops->query_dir_first on the parent directory
+			 * of resolved_path, search for basename of resolved_path and
+			 * check if the ATTR_DIRECTORY is set in fi.Attributes. In some
+			 * case this could work also when opening of the path is denied.
+			 */
+			cifs_dbg(FYI,
+				 "%s: cannot determinate if the symlink target path '%s' "
+				 "is directory or not, creating '%s' as file symlink\n",
+				 __func__, symname, full_path);
+		}
+	}
+
+	kfree(resolved_path);
+	cifs_put_tlink(tlink);
+	return 0;
+}
+
 static int nfs_set_reparse_buf(struct reparse_posix_data *buf,
 			       mode_t mode, dev_t dev,
 			       struct kvec *iov)
@@ -137,7 +295,7 @@ static int mknod_nfs(unsigned int xid, struct inode *inode,
 	};
 
 	new = smb2_get_reparse_inode(&data, inode->i_sb, xid,
-				     tcon, full_path, &iov, NULL);
+				     tcon, full_path, false, &iov, NULL);
 	if (!IS_ERR(new))
 		d_instantiate(dentry, new);
 	else
@@ -283,7 +441,7 @@ static int mknod_wsl(unsigned int xid, struct inode *inode,
 	data.wsl.eas_len = len;
 
 	new = smb2_get_reparse_inode(&data, inode->i_sb,
-				     xid, tcon, full_path,
+				     xid, tcon, full_path, false,
 				     &reparse_iov, &xattr_iov);
 	if (!IS_ERR(new))
 		d_instantiate(dentry, new);

fs/smb/client/smb2inode.c

@@ -1198,6 +1198,7 @@ struct inode *smb2_get_reparse_inode(struct cifs_open_info_data *data,
 				     const unsigned int xid,
 				     struct cifs_tcon *tcon,
 				     const char *full_path,
+				     bool directory,
 				     struct kvec *reparse_iov,
 				     struct kvec *xattr_iov)
 {
@@ -1217,7 +1218,7 @@ struct inode *smb2_get_reparse_inode(struct cifs_open_info_data *data,
 			     FILE_READ_ATTRIBUTES |
 			     FILE_WRITE_ATTRIBUTES,
 			     FILE_CREATE,
-			     CREATE_NOT_DIR | OPEN_REPARSE_POINT,
+			     (directory ? CREATE_NOT_FILE : CREATE_NOT_DIR) | OPEN_REPARSE_POINT,
 			     ACL_NO_MODE);
 	if (xattr_iov)
 		oparms.ea_cctx = xattr_iov;

fs/smb/client/smb2proto.h

@@ -61,6 +61,7 @@ struct inode *smb2_get_reparse_inode(struct cifs_open_info_data *data,
 				     const unsigned int xid,
 				     struct cifs_tcon *tcon,
 				     const char *full_path,
+				     bool directory,
 				     struct kvec *reparse_iov,
 				     struct kvec *xattr_iov);
 int smb2_query_reparse_point(const unsigned int xid,