Re: [PATCH v2 3/3] ksmbd: fill in FileSysIdentifier in FS_POSIX_INFORMATION

[Namjae Jeon]

On Mon, Aug 24, 2026 at 7:23 PM Aleksandr Khromov <haa@xxxxxxxxx> wrote:
>
> smb2_get_info_filesystem() reports 56 bytes for FS_POSIX_INFORMATION,
> that is the whole of FILE_SYSTEM_POSIX_INFO, but never assigns
> FileSysIdentifier.  Those eight bytes go to the client as they are found
> in the response buffer.
>
> The buffer is zeroed on allocation, so a standalone request leaks
> nothing.  A compound request can leak: the offset of the next response
> is advanced by the length pinned for the previous one, so a reply that
> was written into the buffer and then dropped in favour of the short
> error response of smb2_set_err_rsp() stays there, and the next reply is
> laid over it with only the header cleared.
>
> Report the file system id statfs() returned, which is what the field is
> for; ksmbd already hands the same value out in FS_OBJECT_ID_INFORMATION
> when the volume UUID is not available.
>
> Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Aleksandr Khromov <haa@xxxxxxxxx>
> ---
>  fs/smb/server/smb2pdu.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c
> index 5e83ad4f085e..7f200ba103ba 100644
> --- a/fs/smb/server/smb2pdu.c
> +++ b/fs/smb/server/smb2pdu.c
> @@ -6167,6 +6167,8 @@ static int smb2_get_info_filesystem(struct ksmbd_work *work,
>                         info->UserBlocksAvail = cpu_to_le64(stfs.f_bavail);
>                         info->TotalFileNodes = cpu_to_le64(stfs.f_files);
>                         info->FreeFileNodes = cpu_to_le64(stfs.f_ffree);
> +                       memcpy(&info->FileSysIdentifier, &stfs.f_fsid,
> +                              sizeof(stfs.f_fsid));
Since FileSysIdentifier is __le64, endianness conversion is needed.
Thanks.