Commit b07687ed authored by Pali Rohár's avatar Pali Rohár Committed by Steve French
Browse files

cifs: Improve SMB2+ stat() to work also without FILE_READ_ATTRIBUTES 



If SMB2_OP_QUERY_INFO (called when POSIX extensions are not used) failed
with STATUS_ACCESS_DENIED then it means that caller does not have
permission to open the path with FILE_READ_ATTRIBUTES access and therefore
cannot issue SMB2_OP_QUERY_INFO command.

This will result in the -EACCES error from stat() sycall.

There is an alternative way how to query limited information about path but
still suitable for stat() syscall. SMB2 OPEN/CREATE operation returns in
its successful response subset of query information.

So try to open the path without FILE_READ_ATTRIBUTES but with
MAXIMUM_ALLOWED access which will grant the maximum possible access to the
file and the response will contain required query information for stat()
syscall.

This will improve smb2_query_path_info() to query also files which do not
grant FILE_READ_ATTRIBUTES access to caller.

Signed-off-by: default avatarPali Rohár <pali@kernel.org>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent e255612b

fs/smb/client/smb2file.c

+2 −1
Original line number Diff line number Diff line
@@ -158,7 +158,8 @@ int smb2_open_file(const unsigned int xid, struct cifs_open_parms *oparms, __u32 
	if (smb2_path == NULL)

		return -ENOMEM;



	if (!(oparms->desired_access & FILE_READ_ATTRIBUTES)) {

	if (!(oparms->desired_access & FILE_READ_ATTRIBUTES) &&

	    !(oparms->desired_access & MAXIMUM_ALLOWED)) {

		oparms->desired_access |= FILE_READ_ATTRIBUTES;

		retry_without_read_attributes = true;

	}

fs/smb/client/smb2glob.h

+1 −0
Original line number Diff line number Diff line
@@ -38,6 +38,7 @@ enum smb2_compound_ops { 
	SMB2_OP_SET_REPARSE,

	SMB2_OP_GET_REPARSE,

	SMB2_OP_QUERY_WSL_EA,

	SMB2_OP_OPEN_QUERY,

};



/* Used when constructing chained read requests. */

fs/smb/client/smb2inode.c

+66 −1
Original line number Diff line number Diff line
@@ -176,6 +176,7 @@ static int smb2_compound_op(const unsigned int xid, struct cifs_tcon *tcon, 
			    struct kvec *out_iov, int *out_buftype, struct dentry *dentry)

{



	struct smb2_create_rsp *create_rsp = NULL;

	struct smb2_query_info_rsp *qi_rsp = NULL;

	struct smb2_compound_vars *vars = NULL;

	__u8 oplock = SMB2_OPLOCK_LEVEL_NONE;
@@ -265,7 +266,13 @@ static int smb2_compound_op(const unsigned int xid, struct cifs_tcon *tcon, 
	num_rqst++;

	rc = 0;



	for (i = 0; i < num_cmds; i++) {

	i = 0;



	/* Skip the leading explicit OPEN operation */

	if (num_cmds > 0 && cmds[0] == SMB2_OP_OPEN_QUERY)

		i++;



	for (; i < num_cmds; i++) {

		/* Operation */

		switch (cmds[i]) {

		case SMB2_OP_QUERY_INFO:
@@ -640,6 +647,27 @@ static int smb2_compound_op(const unsigned int xid, struct cifs_tcon *tcon, 
	}



	tmp_rc = rc;



	if (rc == 0 && num_cmds > 0 && cmds[0] == SMB2_OP_OPEN_QUERY) {

		create_rsp = rsp_iov[0].iov_base;

		idata = in_iov[0].iov_base;

		idata->fi.CreationTime = create_rsp->CreationTime;

		idata->fi.LastAccessTime = create_rsp->LastAccessTime;

		idata->fi.LastWriteTime = create_rsp->LastWriteTime;

		idata->fi.ChangeTime = create_rsp->ChangeTime;

		idata->fi.Attributes = create_rsp->FileAttributes;

		idata->fi.AllocationSize = create_rsp->AllocationSize;

		idata->fi.EndOfFile = create_rsp->EndofFile;

		if (le32_to_cpu(idata->fi.NumberOfLinks) == 0)

			idata->fi.NumberOfLinks = cpu_to_le32(1); /* dummy value */

		idata->fi.DeletePending = 0;

		idata->fi.Directory = !!(le32_to_cpu(create_rsp->FileAttributes) & ATTR_DIRECTORY);



		/* smb2_parse_contexts() fills idata->fi.IndexNumber */

		rc = smb2_parse_contexts(server, &rsp_iov[0], &oparms->fid->epoch,

					 oparms->fid->lease_key, &oplock, &idata->fi, NULL);

	}



	for (i = 0; i < num_cmds; i++) {

		char *buf = rsp_iov[i + i].iov_base;
@@ -978,6 +1006,43 @@ int smb2_query_path_info(const unsigned int xid, 
	case 0:

		rc = parse_create_response(data, cifs_sb, full_path, &out_iov[0]);

		break;

	case -EACCES:

		/*

		 * If SMB2_OP_QUERY_INFO (called when POSIX extensions are not used) failed with

		 * STATUS_ACCESS_DENIED then it means that caller does not have permission to

		 * open the path with FILE_READ_ATTRIBUTES access and therefore cannot issue

		 * SMB2_OP_QUERY_INFO command.

		 *

		 * There is an alternative way how to query limited information about path but still

		 * suitable for stat() syscall. SMB2 OPEN/CREATE operation returns in its successful

		 * response subset of query information.

		 *

		 * So try to open the path without FILE_READ_ATTRIBUTES but with MAXIMUM_ALLOWED

		 * access which will grant the maximum possible access to the file and the response

		 * will contain required query information for stat() syscall.

		 */



		if (tcon->posix_extensions)

			break;



		num_cmds = 1;

		cmds[0] = SMB2_OP_OPEN_QUERY;

		in_iov[0].iov_base = data;

		in_iov[0].iov_len = sizeof(*data);

		oparms = CIFS_OPARMS(cifs_sb, tcon, full_path, MAXIMUM_ALLOWED,

				     FILE_OPEN, create_options, ACL_NO_MODE);

		free_rsp_iov(out_iov, out_buftype, ARRAY_SIZE(out_iov));

		rc = smb2_compound_op(xid, tcon, cifs_sb, full_path,

				      &oparms, in_iov, cmds, num_cmds,

				      cfile, out_iov, out_buftype, NULL);



		hdr = out_iov[0].iov_base;

		if (!hdr || out_buftype[0] == CIFS_NO_BUFFER)

			goto out;



		if (!rc)

			rc = parse_create_response(data, cifs_sb, full_path, &out_iov[0]);

		break;

	case -EOPNOTSUPP:

		/*

		 * BB TODO: When support for special files added to Samba