From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
To: Florian Weimer <fweimer@redhat.com>,
Adhemerval Zanella via Libc-alpha <libc-alpha@sourceware.org>
Cc: leonardo.macchia@gmail.com
Subject: Re: [PATCH 1/3] inet: Fix getnameinfo (NI_NOFQDN) race condition (BZ#28566)
Date: Thu, 11 Nov 2021 10:34:27 -0300 [thread overview]
Message-ID: <27605b2b-cde0-9b1a-fc97-882d30e30b49@linaro.org> (raw)
In-Reply-To: <87r1bn150g.fsf@oldenburg.str.redhat.com>
On 11/11/2021 05:16, Florian Weimer wrote:
> * Adhemerval Zanella via Libc-alpha:
>
>> diff --git a/inet/getnameinfo.c b/inet/getnameinfo.c
>> index 8380d85783..58ebbb1154 100644
>> --- a/inet/getnameinfo.c
>> +++ b/inet/getnameinfo.c
>> @@ -86,55 +86,75 @@ libc_freeres_ptr (static char *domain);
>> static char *
>> nrl_domainname (void)
>> {
>> + __libc_lock_define_initialized (static, lock);
>> + __libc_lock_lock (lock);
>>
>> + static bool not_first = false;
>> if (! not_first)
>
>> + done:
>> + scratch_buffer_free (&tmpbuf);
>> + not_first = true;
>
> This is missing the acquire/release pairing for the double-checked
> locking idiom. You can probably use the domain variable directly.
But it is done now within the lock, different than current implementation
which does outside. I moved to be within the lock exactly to avoid the
double-checked locking idiom.
I think now that we might be moving to a more optimized lll_lock internally
using a acquire-load+CAS instead of just CAS we can get it without need
to code it explicitly.
>
>> - if ((c = strchr (tmpbuf.data, '.')))
>> + if (h && (c = strchr(h->h_name, '.')))
>
> h != NULL?
I tried to make the code as-is, since is essentially removing a tab;
but I think it makes sense.
>
>> + if (!scratch_buffer_grow_preserve (&tmpbuf))
>
>
> I think the change to _preserve should be in the alloca elimination
> patch (but see my comment there).
Yeah, this is in fact something I did saw on my rebase, but I am
not sure why it is still in the patch submission.
next prev parent reply other threads:[~2021-11-11 13:34 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-10 18:58 [PATCH 0/3] Fixes for getnameinfo() with NI_NOFQDN Adhemerval Zanella
2021-11-10 18:58 ` [PATCH 1/3] inet: Fix getnameinfo (NI_NOFQDN) race condition (BZ#28566) Adhemerval Zanella
2021-11-11 8:16 ` Florian Weimer
2021-11-11 13:34 ` Adhemerval Zanella [this message]
2021-11-11 13:54 ` Florian Weimer
2021-11-11 14:09 ` Adhemerval Zanella
2021-11-11 14:12 ` Florian Weimer
2021-11-11 14:17 ` Adhemerval Zanella
2021-11-11 17:41 ` Florian Weimer
2021-11-10 18:58 ` [PATCH 2/3] inet: Remove strdupa from nrl_domainname() Adhemerval Zanella
2021-11-11 8:18 ` Florian Weimer
2021-11-11 13:36 ` Adhemerval Zanella
2021-11-11 14:00 ` Florian Weimer
2021-11-10 18:58 ` [PATCH 3/3] inet: Return EAI_MEMORY when nrl_domainname() fails to allocate memory Adhemerval Zanella
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