Patchwork getlogin_r: return early when linux sentinel value is set

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Submitter Jesse Hathaway
Date March 26, 2018, 2:22 p.m.
Message ID <CANSNSoX7WFZm9fUEJ43A=CH8tQ+m7ZtGHqJsAfkY-AOqZbFMzA@mail.gmail.com>
Download mbox | patch
Permalink /patch/26481/
State New
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Comments

Jesse Hathaway - March 26, 2018, 2:22 p.m.
On Thu, Mar 22, 2018 at 2:30 PM, Jesse Hathaway <jesse@mbuki-mvuki.org> wrote:
> fixed, attached

Adhemerval Zanella would you be able to push this for me?
Adhemerval Zanella Netto - March 26, 2018, 4:30 p.m.
I will take care of it today, thanks for remind me.

Sent from my iPhone

> On 26 Mar 2018, at 11:22, Jesse Hathaway <jesse@mbuki-mvuki.org> wrote:
> 
>> On Thu, Mar 22, 2018 at 2:30 PM, Jesse Hathaway <jesse@mbuki-mvuki.org> wrote:
>> fixed, attached
> 
> Adhemerval Zanella would you be able to push this for me?
> <getlogin_r.c.patch>
Adhemerval Zanella Netto - March 28, 2018, 12:37 a.m.
Pushed upstream.

On 26/03/2018 13:30, Adhemerval Zanella wrote:
> I will take care of it today, thanks for remind me.
> 
> Sent from my iPhone
> 
>> On 26 Mar 2018, at 11:22, Jesse Hathaway <jesse@mbuki-mvuki.org> wrote:
>>
>>> On Thu, Mar 22, 2018 at 2:30 PM, Jesse Hathaway <jesse@mbuki-mvuki.org> wrote:
>>> fixed, attached
>>
>> Adhemerval Zanella would you be able to push this for me?
>> <getlogin_r.c.patch>
Florian Weimer - April 3, 2018, 10:46 a.m.
On 03/28/2018 02:37 AM, Adhemerval Zanella wrote:
> Pushed upstream.
> 
> On 26/03/2018 13:30, Adhemerval Zanella wrote:
>> I will take care of it today, thanks for remind me.
>>
>> Sent from my iPhone
>>
>>> On 26 Mar 2018, at 11:22, Jesse Hathaway <jesse@mbuki-mvuki.org> wrote:
>>>
>>>> On Thu, Mar 22, 2018 at 2:30 PM, Jesse Hathaway <jesse@mbuki-mvuki.org> wrote:
>>>> fixed, attached
>>>
>>> Adhemerval Zanella would you be able to push this for me?
>>> <getlogin_r.c.patch>

If this has user-visible impact, it should have a bug in Bugzilla, 
referenced from the ChangeLog entry.

Thanks,
Florian
Adhemerval Zanella Netto - April 3, 2018, 11:40 a.m.
On 03/04/2018 07:46, Florian Weimer wrote:
> On 03/28/2018 02:37 AM, Adhemerval Zanella wrote:
>> Pushed upstream.
>>
>> On 26/03/2018 13:30, Adhemerval Zanella wrote:
>>> I will take care of it today, thanks for remind me.
>>>
>>> Sent from my iPhone
>>>
>>>> On 26 Mar 2018, at 11:22, Jesse Hathaway <jesse@mbuki-mvuki.org> wrote:
>>>>
>>>>> On Thu, Mar 22, 2018 at 2:30 PM, Jesse Hathaway <jesse@mbuki-mvuki.org> wrote:
>>>>> fixed, attached
>>>>
>>>> Adhemerval Zanella would you be able to push this for me?
>>>> <getlogin_r.c.patch>
> 
> If this has user-visible impact, it should have a bug in Bugzilla, referenced from the ChangeLog entry.
>

My understanding it is optimization to avoid access nss in
case of invalid uid.
Florian Weimer - April 3, 2018, 11:44 a.m.
On 04/03/2018 01:40 PM, Adhemerval Zanella wrote:
> 
> 
> On 03/04/2018 07:46, Florian Weimer wrote:
>> On 03/28/2018 02:37 AM, Adhemerval Zanella wrote:
>>> Pushed upstream.
>>>
>>> On 26/03/2018 13:30, Adhemerval Zanella wrote:
>>>> I will take care of it today, thanks for remind me.
>>>>
>>>> Sent from my iPhone
>>>>
>>>>> On 26 Mar 2018, at 11:22, Jesse Hathaway <jesse@mbuki-mvuki.org> wrote:
>>>>>
>>>>>> On Thu, Mar 22, 2018 at 2:30 PM, Jesse Hathaway <jesse@mbuki-mvuki.org> wrote:
>>>>>> fixed, attached
>>>>>
>>>>> Adhemerval Zanella would you be able to push this for me?
>>>>> <getlogin_r.c.patch>
>>
>> If this has user-visible impact, it should have a bug in Bugzilla, referenced from the ChangeLog entry.

> My understanding it is optimization to avoid access nss in
> case of invalid uid.

There's a Launchpad bug that suggests a very visible difference in behavior:

https://bugs.launchpad.net/ubuntu/+source/glibc/+bug/1760713

Thanks,
Florian
Adhemerval Zanella Netto - April 3, 2018, 11:53 a.m.
On 03/04/2018 08:44, Florian Weimer wrote:
> On 04/03/2018 01:40 PM, Adhemerval Zanella wrote:
>>
>>
>> On 03/04/2018 07:46, Florian Weimer wrote:
>>> On 03/28/2018 02:37 AM, Adhemerval Zanella wrote:
>>>> Pushed upstream.
>>>>
>>>> On 26/03/2018 13:30, Adhemerval Zanella wrote:
>>>>> I will take care of it today, thanks for remind me.
>>>>>
>>>>> Sent from my iPhone
>>>>>
>>>>>> On 26 Mar 2018, at 11:22, Jesse Hathaway <jesse@mbuki-mvuki.org> wrote:
>>>>>>
>>>>>>> On Thu, Mar 22, 2018 at 2:30 PM, Jesse Hathaway <jesse@mbuki-mvuki.org> wrote:
>>>>>>> fixed, attached
>>>>>>
>>>>>> Adhemerval Zanella would you be able to push this for me?
>>>>>> <getlogin_r.c.patch>
>>>
>>> If this has user-visible impact, it should have a bug in Bugzilla, referenced from the ChangeLog entry.
> 
>> My understanding it is optimization to avoid access nss in
>> case of invalid uid.
> 
> There's a Launchpad bug that suggests a very visible difference in behavior:
> 
> https://bugs.launchpad.net/ubuntu/+source/glibc/+bug/1760713
> 
> Thanks,
> Florian

Alright, https://sourceware.org/bugzilla/show_bug.cgi?id=23024

Patch

commit 7d60c6ab90d23bab16adc2809de95f99e84862d5
Author: Jesse Hathaway <jesse@mbuki-mvuki.org>
Date:   Fri Mar 16 10:46:50 2018 -0500

    getlogin_r: return early when linux sentinel value is set
    
    When there is no login uid Linux sets /proc/self/loginid to the sentinel
    value of, (uid_t) -1. If this is set we can return early and avoid
    needlessly looking up the sentinel value in any configured nss
    databases.

diff --git a/ChangeLog b/ChangeLog
index 3399e567b8..5d776d995f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@ 
+2018-03-20  Jesse Hathaway  <jesse@mbuki-mvuki.org>  (tiny change)
+
+	* sysdeps/unix/sysv/linux/getlogin_r.c (__getlogin_r_loginuid): Return
+	early when linux sentinel value is set.
+
 2018-03-20  Samuel Thibault  <samuel.thibault@ens-lyon.org>
 
 	* manual/errno.texi (EOWNERDEAD, ENOTRECOVERABLE): Remove errno
diff --git a/sysdeps/unix/sysv/linux/getlogin_r.c b/sysdeps/unix/sysv/linux/getlogin_r.c
index 73ea14c8f9..14587712a7 100644
--- a/sysdeps/unix/sysv/linux/getlogin_r.c
+++ b/sysdeps/unix/sysv/linux/getlogin_r.c
@@ -55,6 +55,15 @@  __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, (uid_t) -1, so check if that value is set and return early to
+     avoid making unneeded nss lookups. */
+  if (uid == (uid_t) -1)
+    {
+      __set_errno (ENXIO);
+      return ENXIO;
+    }
+
   struct passwd pwd;
   struct passwd *tpwd;
   int result = 0;