Re: [PATCH v1 20/22] Move common usercopy into security_getpeersec_stream

[Piotr Sawicki]

On 07/16/2018 08:24 PM, Casey Schaufler wrote:
> [PATCH 20/22] Move common usercopy into security_getpeersec_stream
> 
> The modules implementing hook for getpeersec_stream
> don't need to be duplicating the copy-to-user checks.
> Moving the user copy part into the infrastructure makes
> the security module code simpler and reduces the places
> where user copy code may go awry.

Hi,

This change will break the API. Some clients may call getsockopt(..,SO_PEERSEC,..) twice. Firstly, to fetch the length. In that case xxx_socket_getpeersec_stream should return -ERANGE and set *optlen. Secondly, to retrieve a proper security label.

Please take a look at the implementation of the getClientSmackLabel() function in Cynara: https://review.tizen.org/gerrit/#/c/26888/6/src/helpers/creds-socket/creds-socket-inner.cpp
Also there is an email thread about this socket option which tells us why it is made this way: "[RFC] SO_PEERSEC - security credentials for Unix stream sockets"

http://lists.jammed.com/linux-security-module/2003/12/0029.html

Regards,
Piotr