[PATCH] getlogin_r: return early when linux sentinel value is set

[Andreas Schwab]

On Mär 20 2018, Adhemerval Zanella <adhemerval.zanella@linaro.org> wrote:

> On 17/03/2018 00:18, Jesse Hathaway wrote:
>> When there is no login uid Linux sets /proc/self/loginid to the sentinel
>> value of 4294967295. If this is set we can return early and avoid
>> needlessly looking up the sentinel value in any configured nss
>> databases.
>
> The change is short enough so I think it won't require a copyright
> assignment.  However it does require a ChangeLog entry, could you please
> resend the patch with a proper one?
>
>> 
>> diff --git a/sysdeps/unix/sysv/linux/getlogin_r.c
>> b/sysdeps/unix/sysv/linux/getlogin_r.c
>> index 73ea14c8f9..43f55a2188 100644
>> --- a/sysdeps/unix/sysv/linux/getlogin_r.c
>> +++ b/sysdeps/unix/sysv/linux/getlogin_r.c
>> @@ -55,6 +55,12 @@ __getlogin_r_loginuid (char *name, size_t namesize)
>>     endp == uidbuf || *endp != '\0'))
>>      return -1;
>> 
>> +  /* If there is no login uid, linux sets /proc/self/loginid to the sentinel
>> +     value of 4294967295, so check if the value is set and return early to
>> +     avoid making unneeded nss lookups. */
>> +  if (uid == 4294967295)
>> +    return ENXIO;
>
> I prefer to just use either (int)-1 or just 0xffffffff.

That should be (uid_t) -1.

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
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