[libvirt] [PATCH] util: portably check for unchanged uid

[Laine Stump]

On 03/14/2013 06:35 PM, Eric Blake wrote:
> We've already scrubbed for comparisons of 'uid_t == -1' (which fail
> on platforms where uid_t is a u16), but another one snuck in.

ACK (and sorry for the botched "bugfix" :-/)

>
> * src/util/virutil.c (virSetUIDGIDWithCaps): Correct uid comparison.
> * cfg.mk (sc_prohibit_risky_id_promotion): New rule.
> ---
>  cfg.mk             | 6 ++++++
>  src/util/virutil.c | 2 +-
>  2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/cfg.mk b/cfg.mk
> index b95a90b..394521e 100644
> --- a/cfg.mk
> +++ b/cfg.mk
> @@ -389,6 +389,12 @@ sc_prohibit_setuid:
>  	halt='use virSetUIDGID, not raw set*id'				\
>  	  $(_sc_search_regexp)
>
> +# Don't compare *id_t against raw -1.
> +sc_prohibit_risky_id_promotion:
> +	@prohibit='\b(user|group|[ug]id) *[=!]= *-'			\
> +	halt='cast -1 to ([ug]id_t) before comparing against id'	\
> +	  $(_sc_search_regexp)
> +

As we discussed on IRC, I'm slightly concerned about false positives
when user, group, or [gu]id is used as something other than [gu]id_t,
but the most common case of this would be for a char*, and I doubt we
would ever be comparing a char* with !=, so I think it's okay (certainly
better than the alternative of pushing a release only to find that we
don't compile on some platform).