smbd: use metadata_fsp(fsp) in copy_access_posix_acl() for SMB_VFS_SY…

…S_ACL_SET_FD

When inherting permissions on the created stream, we call into the VFS to fetch
the streams security descriptor via inherit_access_posix_acl() ->
copy_access_posix_acl() -> SMB_VFS_SYS_ACL_SET_FD() passing the stream fsp which
triggers the assert SMB_ASSERT(!fsp_is_alternate_stream(fsp)) in
vfswrap_sys_acl_set_fd() in vfs_default.

Just passing the base fsp to the VFS fixes this.

vfs_streams_depot which *does use* distinct backend filesystem files for the
streams, currently does not apply permissions to the stream files at all, so the
incomplete behaviour of vfs_streams_depot is not affected by this change.

If in the future someone want to fix this defficiency in vfs_streams_depot, the
module code can use fsp->stream_fsp to base decisions in VFS ops whether the
module should carry out some action.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15695

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>

Autobuild-User(master): Volker Lendecke <vl@samba.org>
Autobuild-Date(master): Mon Sep  2 08:55:28 UTC 2024 on atb-devel-224

(cherry picked from commit ecb8a99a2c7ba36f9adc50ef13cd8465a0c49b19)

Autobuild-User(v4-20-test): Jule Anger <janger@samba.org>
Autobuild-Date(v4-20-test): Fri Sep  6 15:26:57 UTC 2024 on atb-devel-224

source3/smbd/posix_acls.c

@@ -4000,7 +4000,9 @@ static int copy_access_posix_acl(struct files_struct *from,
 		goto done;
 	}
 
-	ret = SMB_VFS_SYS_ACL_SET_FD(to, SMB_ACL_TYPE_ACCESS, posix_acl);
+	ret = SMB_VFS_SYS_ACL_SET_FD(metadata_fsp(to),
+				     SMB_ACL_TYPE_ACCESS,
+				     posix_acl);
 
  done: