CIFS: Implement follow_link for nounix CIFS mounts

by using a query reparse ioctl request.

Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Pavel Shilovsky <pshilovsky@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/cifspdu.h

@@ -1495,11 +1495,12 @@ struct reparse_data {
 	__u32	ReparseTag;
 	__u16	ReparseDataLength;
 	__u16	Reserved;
-	__u16	AltNameOffset;
-	__u16	AltNameLen;
-	__u16	TargetNameOffset;
-	__u16	TargetNameLen;
-	char	LinkNamesBuf[1];
+	__u16	SubstituteNameOffset;
+	__u16	SubstituteNameLength;
+	__u16	PrintNameOffset;
+	__u16	PrintNameLength;
+	__u32	Flags;
+	char	PathBuffer[0];
 } __attribute__((packed));
 
 struct cifs_quota_data {

fs/cifs/cifsproto.h

@@ -357,13 +357,9 @@ extern int CIFSSMBUnixQuerySymLink(const unsigned int xid,
 			struct cifs_tcon *tcon,
 			const unsigned char *searchName, char **syminfo,
 			const struct nls_table *nls_codepage);
-#ifdef CONFIG_CIFS_SYMLINK_EXPERIMENTAL
-extern int CIFSSMBQueryReparseLinkInfo(const unsigned int xid,
-			struct cifs_tcon *tcon,
-			const unsigned char *searchName,
-			char *symlinkinfo, const int buflen, __u16 fid,
+extern int CIFSSMBQuerySymLink(const unsigned int xid, struct cifs_tcon *tcon,
+			       __u16 fid, char **symlinkinfo,
 			       const struct nls_table *nls_codepage);
-#endif /* temporarily unused until cifs_symlink fixed */
 extern int CIFSSMBOpen(const unsigned int xid, struct cifs_tcon *tcon,
 			const char *fileName, const int disposition,
 			const int access_flags, const int omode,

fs/cifs/cifssmb.c

@@ -3067,7 +3067,6 @@ CIFSSMBUnixQuerySymLink(const unsigned int xid, struct cifs_tcon *tcon,
 	return rc;
 }
 
-#ifdef CONFIG_CIFS_SYMLINK_EXPERIMENTAL
 /*
  *	Recent Windows versions now create symlinks more frequently
  *	and they use the "reparse point" mechanism below.  We can of course
@@ -3079,18 +3078,22 @@ CIFSSMBUnixQuerySymLink(const unsigned int xid, struct cifs_tcon *tcon,
  *	it is not compiled in by default until callers fixed up and more tested.
  */
 int
-CIFSSMBQueryReparseLinkInfo(const unsigned int xid, struct cifs_tcon *tcon,
-			const unsigned char *searchName,
-			char *symlinkinfo, const int buflen, __u16 fid,
+CIFSSMBQuerySymLink(const unsigned int xid, struct cifs_tcon *tcon,
+		    __u16 fid, char **symlinkinfo,
 		    const struct nls_table *nls_codepage)
 {
 	int rc = 0;
 	int bytes_returned;
 	struct smb_com_transaction_ioctl_req *pSMB;
 	struct smb_com_transaction_ioctl_rsp *pSMBr;
+	bool is_unicode;
+	unsigned int sub_len;
+	char *sub_start;
+	struct reparse_data *reparse_buf;
+	__u32 data_offset, data_count;
+	char *end_of_smb;
 
-	cifs_dbg(FYI, "In Windows reparse style QueryLink for path %s\n",
-		 searchName);
+	cifs_dbg(FYI, "In Windows reparse style QueryLink for fid %u\n", fid);
 	rc = smb_init(SMB_COM_NT_TRANSACT, 23, tcon, (void **) &pSMB,
 		      (void **) &pSMBr);
 	if (rc)
@@ -3119,66 +3122,55 @@ CIFSSMBQueryReparseLinkInfo(const unsigned int xid, struct cifs_tcon *tcon,
 			 (struct smb_hdr *) pSMBr, &bytes_returned, 0);
 	if (rc) {
 		cifs_dbg(FYI, "Send error in QueryReparseLinkInfo = %d\n", rc);
-	} else {		/* decode response */
-		__u32 data_offset = le32_to_cpu(pSMBr->DataOffset);
-		__u32 data_count = le32_to_cpu(pSMBr->DataCount);
+		goto qreparse_out;
+	}
+
+	data_offset = le32_to_cpu(pSMBr->DataOffset);
+	data_count = le32_to_cpu(pSMBr->DataCount);
 	if (get_bcc(&pSMBr->hdr) < 2 || data_offset > 512) {
 		/* BB also check enough total bytes returned */
 		rc = -EIO;	/* bad smb */
 		goto qreparse_out;
 	}
-		if (data_count && (data_count < 2048)) {
-			char *end_of_smb = 2 /* sizeof byte count */ +
-			       get_bcc(&pSMBr->hdr) + (char *)&pSMBr->ByteCount;
-
-			struct reparse_data *reparse_buf =
-						(struct reparse_data *)
-						((char *)&pSMBr->hdr.Protocol
-								 + data_offset);
+	if (!data_count || (data_count > 2048)) {
+		rc = -EIO;
+		cifs_dbg(FYI, "Invalid return data count on get reparse info ioctl\n");
+		goto qreparse_out;
+	}
+	end_of_smb = 2 + get_bcc(&pSMBr->hdr) + (char *)&pSMBr->ByteCount;
+	reparse_buf = (struct reparse_data *)
+				((char *)&pSMBr->hdr.Protocol + data_offset);
 	if ((char *)reparse_buf >= end_of_smb) {
 		rc = -EIO;
 		goto qreparse_out;
 	}
-			if ((reparse_buf->LinkNamesBuf +
-				reparse_buf->TargetNameOffset +
-				reparse_buf->TargetNameLen) > end_of_smb) {
+	if ((reparse_buf->PathBuffer + reparse_buf->PrintNameOffset +
+				reparse_buf->PrintNameLength) > end_of_smb) {
 		cifs_dbg(FYI, "reparse buf beyond SMB\n");
 		rc = -EIO;
 		goto qreparse_out;
 	}
+	sub_start = reparse_buf->SubstituteNameOffset + reparse_buf->PathBuffer;
+	sub_len = reparse_buf->SubstituteNameLength;
+	if (pSMBr->hdr.Flags2 & SMBFLG2_UNICODE)
+		is_unicode = true;
+	else
+		is_unicode = false;
 
-			if (pSMBr->hdr.Flags2 & SMBFLG2_UNICODE) {
-				cifs_from_ucs2(symlinkinfo, (__le16 *)
-						(reparse_buf->LinkNamesBuf +
-						reparse_buf->TargetNameOffset),
-						buflen,
-						reparse_buf->TargetNameLen,
-						nls_codepage, 0);
-			} else { /* ASCII names */
-				strncpy(symlinkinfo,
-					reparse_buf->LinkNamesBuf +
-					reparse_buf->TargetNameOffset,
-					min_t(const int, buflen,
-					   reparse_buf->TargetNameLen));
-			}
-		} else {
-			rc = -EIO;
-			cifs_dbg(FYI, "Invalid return data count on get reparse info ioctl\n");
-		}
-		symlinkinfo[buflen] = 0; /* just in case so the caller
-					does not go off the end of the buffer */
-		cifs_dbg(FYI, "readlink result - %s\n", symlinkinfo);
-	}
-
+	/* BB FIXME investigate remapping reserved chars here */
+	*symlinkinfo = cifs_strndup_from_utf16(sub_start, sub_len, is_unicode,
+					       nls_codepage);
+	if (!*symlinkinfo)
+		rc = -ENOMEM;
 qreparse_out:
 	cifs_buf_release(pSMB);
 
-	/* Note: On -EAGAIN error only caller can retry on handle based calls
-		since file handle passed in no longer valid */
-
+	/*
+	 * Note: On -EAGAIN error only caller can retry on handle based calls
+	 * since file handle passed in no longer valid.
+	 */
 	return rc;
 }
-#endif /* CIFS_SYMLINK_EXPERIMENTAL */ /* BB temporarily unused */
 
 #ifdef CONFIG_CIFS_POSIX
 

fs/cifs/smb1ops.c

@@ -881,6 +881,37 @@ cifs_mand_lock(const unsigned int xid, struct cifsFileInfo *cfile, __u64 offset,
 			   (__u8)type, wait, 0);
 }
 
+static int
+cifs_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;
+	int oplock = 0;
+	__u16 netfid;
+
+	cifs_dbg(FYI, "%s: path: %s\n", __func__, full_path);
+
+	rc = CIFSSMBOpen(xid, tcon, full_path, FILE_OPEN,
+			 FILE_READ_ATTRIBUTES, OPEN_REPARSE_POINT, &netfid,
+			 &oplock, NULL, cifs_sb->local_nls,
+			 cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
+	if (rc)
+		return rc;
+
+	rc = CIFSSMBQuerySymLink(xid, tcon, netfid, target_path,
+				 cifs_sb->local_nls);
+	if (rc) {
+		CIFSSMBClose(xid, tcon, netfid);
+		return rc;
+	}
+
+	convert_delimiter(*target_path, '/');
+	CIFSSMBClose(xid, tcon, netfid);
+	cifs_dbg(FYI, "%s: target path: %s\n", __func__, *target_path);
+	return rc;
+}
+
 struct smb_version_operations smb1_operations = {
 	.send_cancel = send_nt_cancel,
 	.compare_fids = cifs_compare_fids,
@@ -927,6 +958,7 @@ struct smb_version_operations smb1_operations = {
 	.rename_pending_delete = cifs_rename_pending_delete,
 	.rename = CIFSSMBRename,
 	.create_hardlink = CIFSCreateHardLink,
+	.query_symlink = cifs_query_symlink,
 	.open = cifs_open_file,
 	.set_fid = cifs_set_fid,
 	.close = cifs_close_file,