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: Pali Rohár <pali@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/smb/client/smb2file.c b/fs/smb/client/smb2file.c
index 2d726e9b950cf4069642b376dfd5441d2c2c856a..5d60410460d2b95db9ac871bde87d3aa9d75383c 100644 (file)
--- a/fs/smb/client/smb2file.c
+++ b/fs/smb/client/smb2file.c
@@ -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;
        }

diff --git a/fs/smb/client/smb2glob.h b/fs/smb/client/smb2glob.h
index 2466e61551369c883db6fdfd95d82cf4e9a0a254..224495322a05dab073be7447690cdaab79e2d938 100644 (file)
--- a/fs/smb/client/smb2glob.h
+++ b/fs/smb/client/smb2glob.h
@@ -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. */

diff --git a/fs/smb/client/smb2inode.c b/fs/smb/client/smb2inode.c
index e9fd3e204a6f4081e9d3b99a1de19e21b2fd3f6c..57d9bfbadd97b2b38cbfc938dafe5e0ec080850e 100644 (file)
--- a/fs/smb/client/smb2inode.c
+++ b/fs/smb/client/smb2inode.c
@@ -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 @@ replay_again:
        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 @@ finished:
        }
 
        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