Re: [Qemu-devel] [PATCH] virtfs-proxy-helper: check return code of setfsgid/setfsuid

[Stefan Weil <sw@weilnetz.de>]

Am 10.10.2012 13:32, schrieb Paolo Bonzini:
> Fixes the following error with glibc 2.16 on Fedora 18:
>
> virtfs-proxy-helper.c: In function ‘setfsugid’:
> virtfs-proxy-helper.c:293:13: error: ignoring return value of ‘setfsgid’, declared with attribute warn_unused_result [-Werror=unused-result]
> virtfs-proxy-helper.c:294:13: error: ignoring return value of ‘setfsuid’, declared with attribute warn_unused_result [-Werror=unused-result]
> cc1: all warnings being treated as errors
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   fsdev/virtfs-proxy-helper.c | 8 ++++++--
>   1 file modificato, 6 inserzioni(+), 2 rimozioni(-)
>
> diff --git a/fsdev/virtfs-proxy-helper.c b/fsdev/virtfs-proxy-helper.c
> index f9a8270..b34a84a 100644
> --- a/fsdev/virtfs-proxy-helper.c
> +++ b/fsdev/virtfs-proxy-helper.c
> @@ -290,8 +290,12 @@ static int setfsugid(int uid, int gid)
>           CAP_DAC_OVERRIDE,
>       };
>   
> -    setfsgid(gid);
> -    setfsuid(uid);
> +    if (setfsgid(gid) != 0) {
> +        return -1;
> +    }

Wouldn't setfsgid(gid) == gid be also ok?

I have no idea whether it is a realistic scenario to call
that function with a gid which is already set.


> +    if (setfsuid(uid) != 0) {
> +        return -1;
> +    }
>   

The same question applies here.

>       if (uid != 0 || gid != 0) {
>           return do_cap_set(cap_list, ARRAY_SIZE(cap_list), 0);

The Linux manpage for both functions says something
completely different. Extract from manpage of setfsuid:

"On success, the previous value of fsuid is returned.
  On error, the current value of fsuid is returned."

In reality, the functions return 0 when called by root.

Regards

Stefan