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Re: [libvirt] [PATCH 05/15] util: make virSetUIDGID a NOP when uid or gid is -1



On 02/07/2013 02:37 PM, Laine Stump wrote:
> setregid() and setreuid() already interpret -1 as a NOP, so this is
> just an optimization for those, but we are also calling getpwuid_r and
> initgroups, and it's unclear what the former would do with a uid of
> -1.
> ---
>  src/util/virutil.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/src/util/virutil.c b/src/util/virutil.c
> index 24ba954..fddc39e 100644
> --- a/src/util/virutil.c
> +++ b/src/util/virutil.c
> @@ -2687,7 +2687,7 @@ virSetUIDGID(uid_t uid, gid_t gid)
>      int err;
>      char *buf = NULL;
>  
> -    if (gid > 0) {
> +    if (gid != -1 && gid > 0) {

gid_t might be an unsigned type, or it might be a signed type.  Really,
the only time we should not attempt setregid is if it it was -1; or if
we are optimizing for gid==0; but we can't really use gid > 0 as a valid
test.  Also, the width of gid_t is not mandated by POSIX, so the only
portable way to compare to -1 is with a cast.  I think you want:

if (gid && gid != (gid_t)-1) {

> @@ -2696,7 +2696,7 @@ virSetUIDGID(uid_t uid, gid_t gid)
>          }
>      }
>  
> -    if (uid > 0) {
> +    if (uid != -1 && uid > 0) {

Likewise, you want:

if (uid && uid != (uid_t)-1) {

I'm not clear on whether avoiding these functions for uid/gid==0 makes
sense, or if you instead want:

if (uid != (uid_t)-1) {

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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