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

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Message-Id: <20241222154340.24104-5-pali@kernel.org>
Date: Sun, 22 Dec 2024 16:43:40 +0100
From: Pali Rohár <pali@...nel.org>
To: Steve French <sfrench@...ba.org>,
	Paulo Alcantara <pc@...guebit.com>,
	Ronnie Sahlberg <ronniesahlberg@...il.com>
Cc: linux-cifs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 4/4] cifs: Check if server supports reparse points before using them

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@...nel.org>
---
 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