[PATCH v2 2/2] cifs: Improve stat() to work also without FILE_READ_ATTRIBUTES
From: Pali Rohár
Date: Sun Dec 22 2024 - 08:21:43 EST
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@xxxxxxxxxx>
---
fs/smb/client/cifspdu.h | 1 +
fs/smb/client/smb2file.c | 3 +-
fs/smb/client/smb2glob.h | 1 +
fs/smb/client/smb2inode.c | 71 ++++++++++++++++++++++++++++++++++++++-
4 files changed, 74 insertions(+), 2 deletions(-)
diff --git a/fs/smb/client/cifspdu.h b/fs/smb/client/cifspdu.h
index ee78bb6741d6..d0e7fbc5cacd 100644
--- a/fs/smb/client/cifspdu.h
+++ b/fs/smb/client/cifspdu.h
@@ -217,6 +217,7 @@
/* of an input/output request */
#define SYSTEM_SECURITY 0x01000000 /* The system access control list */
/* can be read and changed */
+#define MAXIMUM_ALLOWED 0x02000000
#define GENERIC_ALL 0x10000000
#define GENERIC_EXECUTE 0x20000000
#define GENERIC_WRITE 0x40000000
diff --git a/fs/smb/client/smb2file.c b/fs/smb/client/smb2file.c
index ff255fdc4532..1476cb824ae4 100644
--- 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 2466e6155136..224495322a05 100644
--- 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 e8bb3f8b53f1..379ac3cbad1f 100644
--- a/fs/smb/client/smb2inode.c
+++ b/fs/smb/client/smb2inode.c
@@ -188,6 +188,7 @@ static int smb2_compound_op(const unsigned int xid, struct cifs_tcon *tcon,
struct TCP_Server_Info *server;
int num_rqst = 0, i;
int resp_buftype[MAX_COMPOUND];
+ struct smb2_create_rsp *create_rsp = NULL;
struct smb2_query_info_rsp *qi_rsp = NULL;
struct cifs_open_info_data *idata;
struct inode *inode = NULL;
@@ -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:
@@ -637,6 +644,26 @@ static int smb2_compound_op(const unsigned int xid, struct cifs_tcon *tcon,
tcon->need_reconnect = true;
}
+ 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++) {
switch (cmds[i]) {
case SMB2_OP_QUERY_INFO:
@@ -934,6 +961,48 @@ 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;
+
+ for (i = 0; i < ARRAY_SIZE(out_buftype); i++) {
+ free_rsp_buf(out_buftype[i], out_iov[i].iov_base);
+ out_buftype[i] = 0;
+ out_iov[i].iov_base = NULL;
+ }
+
+ 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);
+ 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
--
2.20.1