[PATCH AUTOSEL 6.1 003/212] cifs: Add fallback for SMB2 CREATE without FILE_READ_ATTRIBUTES

Sasha Levin
2025-05-05T23:06:32Z

[ Upstream commit e255612b5ed9f179abe8196df7c2ba09dd227900 ]

Some operations, like WRITE, does not require FILE_READ_ATTRIBUTES access.

So when FILE_READ_ATTRIBUTES is not explicitly requested for
smb2_open_file() then first try to do SMB2 CREATE with FILE_READ_ATTRIBUTES
access (like it was before) and then fallback to SMB2 CREATE without
FILE_READ_ATTRIBUTES access (less common case).

This change allows to complete WRITE operation to a file when it does not
grant FILE_READ_ATTRIBUTES permission and its parent directory does not
grant READ_DATA permission (parent directory READ_DATA is implicit grant of
child FILE_READ_ATTRIBUTES permission).

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/smb/client/smb2file.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/fs/smb/client/smb2file.c b/fs/smb/client/smb2file.c
index a7475bc05cac0..afdc78e92ee9b 100644
--- a/fs/smb/client/smb2file.c
+++ b/fs/smb/client/smb2file.c
@@ -108,16 +108,25 @@ int smb2_open_file(const unsigned int xid, struct cifs_open_parms *oparms, __u32
int err_buftype = CIFS_NO_BUFFER;
struct cifs_fid *fid = oparms->fid;
struct network_resiliency_req nr_ioctl_req;
+ bool retry_without_read_attributes = false;

smb2_path = cifs_convert_path_to_utf16(oparms->path, oparms->cifs_sb);
if (smb2_path == NULL)
return -ENOMEM;

- oparms->desired_access |= FILE_READ_ATTRIBUTES;
+ if (!(oparms->desired_access & FILE_READ_ATTRIBUTES)) {
+ oparms->desired_access |= FILE_READ_ATTRIBUTES;
+ retry_without_read_attributes = true;
+ }
smb2_oplock = SMB2_OPLOCK_LEVEL_BATCH;

rc = SMB2_open(xid, oparms, smb2_path, &smb2_oplock, smb2_data, NULL, &err_iov,
&err_buftype);
+ if (rc == -EACCES && retry_without_read_attributes) {
+ oparms->desired_access &= ~FILE_READ_ATTRIBUTES;
+ rc = SMB2_open(xid, oparms, smb2_path, &smb2_oplock, smb2_data, NULL, &err_iov,
+ &err_buftype);
+ }
if (rc && data) {
struct smb2_hdr *hdr = err_iov.iov_base;

--
2.39.5