[PATCH 4/4] cifs: Check if server supports reparse points before using them

[Pali Rohár <pali@xxxxxxxxxx>]

Do not attempt to query or create reparse point when server fs does not
support it. This will prevent creating unusable empty object on the server.

Signed-off-by: Pali Rohár <pali@xxxxxxxxxx>
---
 fs/smb/client/cifssmb.c   | 3 +++
 fs/smb/client/link.c      | 3 ++-
 fs/smb/client/smb2inode.c | 8 ++++++++
 fs/smb/client/smb2ops.c   | 4 ++--
 4 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/fs/smb/client/cifssmb.c b/fs/smb/client/cifssmb.c
index 2763db49b155..83365861a99c 100644
--- a/fs/smb/client/cifssmb.c
+++ b/fs/smb/client/cifssmb.c
@@ -2695,6 +2695,9 @@ int cifs_query_reparse_point(const unsigned int xid,
 	if (cap_unix(tcon->ses))
 		return -EOPNOTSUPP;
 
+	if (!(le32_to_cpu(tcon->fsAttrInfo.Attributes) & FILE_SUPPORTS_REPARSE_POINTS))
+		return -EOPNOTSUPP;
+
 	oparms = (struct cifs_open_parms) {
 		.tcon = tcon,
 		.cifs_sb = cifs_sb,
diff --git a/fs/smb/client/link.c b/fs/smb/client/link.c
index 6e6c09cc5ce7..a88253668286 100644
--- a/fs/smb/client/link.c
+++ b/fs/smb/client/link.c
@@ -643,7 +643,8 @@ cifs_symlink(struct mnt_idmap *idmap, struct inode *inode,
 	case CIFS_SYMLINK_TYPE_NATIVE:
 	case CIFS_SYMLINK_TYPE_NFS:
 	case CIFS_SYMLINK_TYPE_WSL:
-		if (server->ops->create_reparse_symlink) {
+		if (server->ops->create_reparse_symlink &&
+		    (le32_to_cpu(pTcon->fsAttrInfo.Attributes) & FILE_SUPPORTS_REPARSE_POINTS)) {
 			rc = server->ops->create_reparse_symlink(xid, inode,
 								 direntry,
 								 pTcon,
diff --git a/fs/smb/client/smb2inode.c b/fs/smb/client/smb2inode.c
index 379ac3cbad1f..818537c83d41 100644
--- a/fs/smb/client/smb2inode.c
+++ b/fs/smb/client/smb2inode.c
@@ -1289,6 +1289,14 @@ struct inode *smb2_get_reparse_inode(struct cifs_open_info_data *data,
 	int rc;
 	int i;
 
+	/*
+	 * If server filesystem does not support reparse points then do not
+	 * attempt to create reparse point. This will prevent creating unusable
+	 * empty object on the server.
+	 */
+	if (!(le32_to_cpu(tcon->fsAttrInfo.Attributes) & FILE_SUPPORTS_REPARSE_POINTS))
+		return ERR_PTR(-EOPNOTSUPP);
+
 	oparms = CIFS_OPARMS(cifs_sb, tcon, full_path,
 			     SYNCHRONIZE | DELETE |
 			     FILE_READ_ATTRIBUTES |
diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index 0a91f18d4a54..50adb5cdfce9 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -5202,7 +5202,7 @@ static int smb2_make_node(unsigned int xid, struct inode *inode,
 			  const char *full_path, umode_t mode, dev_t dev)
 {
 	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
-	int rc;
+	int rc = -EOPNOTSUPP;
 
 	/*
 	 * Check if mounted with mount parm 'sfu' mount parm.
@@ -5213,7 +5213,7 @@ static int smb2_make_node(unsigned int xid, struct inode *inode,
 	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_UNX_EMUL) {
 		rc = cifs_sfu_make_node(xid, inode, dentry, tcon,
 					full_path, mode, dev);
-	} else {
+	} else if (le32_to_cpu(tcon->fsAttrInfo.Attributes) & FILE_SUPPORTS_REPARSE_POINTS) {
 		rc = smb2_mknod_reparse(xid, inode, dentry, tcon,
 					full_path, mode, dev);
 	}
-- 
2.20.1