CIFS: Fix symbolic links usage

Now we treat any reparse point as a symbolic link and map it to a Unix
one that is not true in a common case due to many reparse point types
supported by SMB servers.

Distinguish reparse point types into two groups:
1) that can be accessed directly through a reparse point
(junctions, deduplicated files, NFS symlinks);
2) that need to be processed manually (Windows symbolic links, DFS);

and map only Windows symbolic links to Unix ones.

Cc: <stable@vger.kernel.org>
Acked-by: NJeff Layton <jlayton@redhat.com>
Reported-and-tested-by: NJoao Correia <joaomiguelcorreia@gmail.com>
Signed-off-by: NPavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: NSteve French <smfrench@gmail.com>

fs/cifs/cifsglob.h

@@ -261,7 +261,7 @@ struct smb_version_operations {
 	/* query path data from the server */
 	int (*query_path_info)(const unsigned int, struct cifs_tcon *,
 			       struct cifs_sb_info *, const char *,
-			       FILE_ALL_INFO *, bool *);
+			       FILE_ALL_INFO *, bool *, bool *);
 	/* query file data from the server */
 	int (*query_file_info)(const unsigned int, struct cifs_tcon *,
 			       struct cifs_fid *, FILE_ALL_INFO *);

fs/cifs/inode.c

@@ -542,7 +542,8 @@ static int cifs_sfu_mode(struct cifs_fattr *fattr, const unsigned char *path,
 /* Fill a cifs_fattr struct with info from FILE_ALL_INFO */
 static void
 cifs_all_info_to_fattr(struct cifs_fattr *fattr, FILE_ALL_INFO *info,
-		       struct cifs_sb_info *cifs_sb, bool adjust_tz)
+		       struct cifs_sb_info *cifs_sb, bool adjust_tz,
+		       bool symlink)
 {
 	struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
 
@@ -569,7 +570,11 @@ cifs_all_info_to_fattr(struct cifs_fattr *fattr, FILE_ALL_INFO *info,
 	fattr->cf_createtime = le64_to_cpu(info->CreationTime);
 
 	fattr->cf_nlink = le32_to_cpu(info->NumberOfLinks);
-	if (fattr->cf_cifsattrs & ATTR_DIRECTORY) {
+
+	if (symlink) {
+		fattr->cf_mode = S_IFLNK;
+		fattr->cf_dtype = DT_LNK;
+	} else if (fattr->cf_cifsattrs & ATTR_DIRECTORY) {
 		fattr->cf_mode = S_IFDIR | cifs_sb->mnt_dir_mode;
 		fattr->cf_dtype = DT_DIR;
 		/*
@@ -578,10 +583,6 @@ cifs_all_info_to_fattr(struct cifs_fattr *fattr, FILE_ALL_INFO *info,
 		 */
 		if (!tcon->unix_ext)
 			fattr->cf_flags |= CIFS_FATTR_UNKNOWN_NLINK;
-	} 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;
@@ -626,7 +627,8 @@ cifs_get_file_info(struct file *filp)
 	rc = server->ops->query_file_info(xid, tcon, &cfile->fid, &find_data);
 	switch (rc) {
 	case 0:
-		cifs_all_info_to_fattr(&fattr, &find_data, cifs_sb, false);
+		cifs_all_info_to_fattr(&fattr, &find_data, cifs_sb, false,
+				       false);
 		break;
 	case -EREMOTE:
 		cifs_create_dfs_fattr(&fattr, inode->i_sb);
@@ -673,6 +675,7 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
 	bool adjust_tz = false;
 	struct cifs_fattr fattr;
 	struct cifs_search_info *srchinf = NULL;
+	bool symlink = false;
 
 	tlink = cifs_sb_tlink(cifs_sb);
 	if (IS_ERR(tlink))
@@ -702,12 +705,12 @@ cifs_get_inode_info(struct inode **inode, const char *full_path,
 		}
 		data = (FILE_ALL_INFO *)buf;
 		rc = server->ops->query_path_info(xid, tcon, cifs_sb, full_path,
-						  data, &adjust_tz);
+						  data, &adjust_tz, &symlink);
 	}
 
 	if (!rc) {
-		cifs_all_info_to_fattr(&fattr, (FILE_ALL_INFO *)data, cifs_sb,
-				       adjust_tz);
+		cifs_all_info_to_fattr(&fattr, data, cifs_sb, adjust_tz,
+				       symlink);
 	} else if (rc == -EREMOTE) {
 		cifs_create_dfs_fattr(&fattr, sb);
 		rc = 0;

fs/cifs/readdir.c

@@ -134,22 +134,6 @@ cifs_prime_dcache(struct dentry *parent, struct qstr *name,
 	dput(dentry);
 }
 
-/*
- * Is it possible that this directory might turn out to be a DFS referral
- * once we go to try and use it?
- */
-static bool
-cifs_dfs_is_possible(struct cifs_sb_info *cifs_sb)
-{
-#ifdef CONFIG_CIFS_DFS_UPCALL
-	struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
-
-	if (tcon->Flags & SMB_SHARE_IS_IN_DFS)
-		return true;
-#endif
-	return false;
-}
-
 static void
 cifs_fill_common_info(struct cifs_fattr *fattr, struct cifs_sb_info *cifs_sb)
 {
@@ -159,27 +143,19 @@ cifs_fill_common_info(struct cifs_fattr *fattr, struct cifs_sb_info *cifs_sb)
 	if (fattr->cf_cifsattrs & ATTR_DIRECTORY) {
 		fattr->cf_mode = S_IFDIR | cifs_sb->mnt_dir_mode;
 		fattr->cf_dtype = DT_DIR;
-		/*
-		 * Windows CIFS servers generally make DFS referrals look
-		 * like directories in FIND_* responses with the reparse
-		 * attribute flag also set (since DFS junctions are
-		 * reparse points). We must revalidate at least these
-		 * directory inodes before trying to use them (if
-		 * they are DFS we will get PATH_NOT_COVERED back
-		 * when queried directly and can then try to connect
-		 * to the DFS target)
-		 */
-		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;
 	}
 
+	/*
+	 * We need to revalidate it further to make a decision about whether it
+	 * is a symbolic link, DFS referral or a reparse point with a direct
+	 * access like junctions, deduplicated files, NFS symlinks.
+	 */
+	if (fattr->cf_cifsattrs & ATTR_REPARSE)
+		fattr->cf_flags |= CIFS_FATTR_NEED_REVAL;
+
 	/* non-unix readdir doesn't provide nlink */
 	fattr->cf_flags |= CIFS_FATTR_UNKNOWN_NLINK;
 

fs/cifs/smb1ops.c

@@ -534,10 +534,12 @@ cifs_is_path_accessible(const unsigned int xid, struct cifs_tcon *tcon,
 static int
 cifs_query_path_info(const unsigned int xid, struct cifs_tcon *tcon,
 		     struct cifs_sb_info *cifs_sb, const char *full_path,
-		     FILE_ALL_INFO *data, bool *adjustTZ)
+		     FILE_ALL_INFO *data, bool *adjustTZ, bool *symlink)
 {
 	int rc;
 
+	*symlink = false;
+
 	/* could do find first instead but this returns more info */
 	rc = CIFSSMBQPathInfo(xid, tcon, full_path, data, 0 /* not legacy */,
 			      cifs_sb->local_nls, cifs_sb->mnt_cifs_flags &
@@ -554,6 +556,23 @@ cifs_query_path_info(const unsigned int xid, struct cifs_tcon *tcon,
 						CIFS_MOUNT_MAP_SPECIAL_CHR);
 		*adjustTZ = true;
 	}
+
+	if (!rc && (le32_to_cpu(data->Attributes) & ATTR_REPARSE)) {
+		int tmprc;
+		int oplock = 0;
+		__u16 netfid;
+
+		/* Need to check if this is a symbolic link or not */
+		tmprc = CIFSSMBOpen(xid, tcon, full_path, FILE_OPEN,
+				    FILE_READ_ATTRIBUTES, 0, &netfid, &oplock,
+				    NULL, cifs_sb->local_nls,
+			cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
+		if (tmprc == -EOPNOTSUPP)
+			*symlink = true;
+		else
+			CIFSSMBClose(xid, tcon, netfid);
+	}
+
 	return rc;
 }
 

fs/cifs/smb2inode.c

@@ -123,22 +123,30 @@ move_smb2_info_to_cifs(FILE_ALL_INFO *dst, struct smb2_file_all_info *src)
 int
 smb2_query_path_info(const unsigned int xid, struct cifs_tcon *tcon,
 		     struct cifs_sb_info *cifs_sb, const char *full_path,
-		     FILE_ALL_INFO *data, bool *adjust_tz)
+		     FILE_ALL_INFO *data, bool *adjust_tz, bool *symlink)
 {
 	int rc;
 	struct smb2_file_all_info *smb2_data;
 
 	*adjust_tz = false;
+	*symlink = false;
 
 	smb2_data = kzalloc(sizeof(struct smb2_file_all_info) + MAX_NAME * 2,
 			    GFP_KERNEL);
 	if (smb2_data == NULL)
 		return -ENOMEM;
 
+	rc = smb2_open_op_close(xid, tcon, cifs_sb, full_path,
+				FILE_READ_ATTRIBUTES, FILE_OPEN, 0,
+				smb2_data, SMB2_OP_QUERY_INFO);
+	if (rc == -EOPNOTSUPP) {
+		*symlink = true;
+		/* Failed on a symbolic link - query a reparse point info */
 		rc = smb2_open_op_close(xid, tcon, cifs_sb, full_path,
 					FILE_READ_ATTRIBUTES, FILE_OPEN,
 					OPEN_REPARSE_POINT, smb2_data,
 					SMB2_OP_QUERY_INFO);
+	}
 	if (rc)
 		goto out;
 

fs/cifs/smb2proto.h

@@ -61,7 +61,7 @@ extern void move_smb2_info_to_cifs(FILE_ALL_INFO *dst,
 extern int smb2_query_path_info(const unsigned int xid, struct cifs_tcon *tcon,
 				struct cifs_sb_info *cifs_sb,
 				const char *full_path, FILE_ALL_INFO *data,
-				bool *adjust_tz);
+				bool *adjust_tz, bool *symlink);
 extern int smb2_set_path_size(const unsigned int xid, struct cifs_tcon *tcon,
 			      const char *full_path, __u64 size,
 			      struct cifs_sb_info *cifs_sb, bool set_alloc);