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

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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>
This commit is contained in:
Pali Rohár 2024-10-05 14:59:21 +02:00 committed by Steve French
parent e255612b5e
commit b07687edee
3 changed files with 69 additions and 2 deletions
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3
fs/smb/client/smb2file.c
View File

@ -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;
}

1
fs/smb/client/smb2glob.h
View File

@ -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. */

67
fs/smb/client/smb2inode.c
View File

@ -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