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>

1 files changed, 57 insertions, 3 deletions

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index f259e6c..91b9e54 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,