Re: [PATCH 3/5] cifs: Fix validation of SMB2_OP_QUERY_WSL_EA response size

[Paulo Alcantara <pc@manguebit.com>]

Pali Rohár <pali@kernel.org> writes:

> Currently the SMB2_OP_QUERY_WSL_EA checks that response buffer has at least
> size SMB2_WSL_MIN_QUERY_EA_RESP_SIZE and maximally it is
> SMB2_WSL_MAX_QUERY_EA_RESP_SIZE.
>
> Constant SMB2_WSL_MIN_QUERY_EA_RESP_SIZE is defined wrongly because it
> expects that the there are at least 3 EAs. But WSL subsystem has only one
> mandatory EA: $LXMOD. So fix the SMB2_WSL_MIN_QUERY_EA_RESP_SIZE to be size
> of the structure of one EA.
>
> Relax also SMB2_WSL_MAX_QUERY_EA_RESP_SIZE, calculate maximum size from the
> size of the largest EA which is 8 bytes for $LXDEV.
>
> This change allows to recognize WSL CHR and BLK reparse points which have
> only $LXMOD and $LXDEV EAs (no $LXUID or $LXGID). WSL subsystem recognize
> such reparse points too.
>
> Fixes: ea41367b2a60 ("smb: client: introduce SMB2_OP_QUERY_WSL_EA")
> Signed-off-by: Pali Rohár <pali@kernel.org>
> ---
>  fs/smb/client/smb2pdu.h | 19 +++++++++----------
>  1 file changed, 9 insertions(+), 10 deletions(-)

If we're querying all those EAs and the file has only $LXMOD, wouldn't
the server return empty EAs except for $LXMOD?