From: DJ Delorie <dj@redhat.com>
To: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Cc: libc-alpha@sourceware.org
Subject: Re: [PATCH v2 1/3] inet: Fix getnameinfo (NI_NOFQDN) race condition (BZ#28566)
Date: Mon, 07 Mar 2022 22:44:21 -0500 [thread overview]
Message-ID: <xnpmmx5cru.fsf@greed.delorie.com> (raw)
In-Reply-To: <20211210110733.1499984-2-adhemerval.zanella@linaro.org> (message from Adhemerval Zanella via Libc-alpha on Fri, 10 Dec 2021 08:07:31 -0300)
Reviewing the resulting text intead of the patch, because... easier?
Adhemerval Zanella via Libc-alpha <libc-alpha@sourceware.org> writes:
> static void
> nrl_domainname_core (struct scratch_buffer *tmpbuf)
> {
> char *c;
> struct hostent *h, th;
> int herror;
>
> while (__gethostbyname_r ("localhost", &th,
> tmpbuf->data, tmpbuf->length,
> &h, &herror))
> {
> if (herror == NETDB_INTERNAL && errno == ERANGE)
> {
> if (!scratch_buffer_grow (tmpbuf))
> return;
> }
> else
> break;
> }
Ok.
> if (h != NULL && (c = strchr (h->h_name, '.')) != NULL)
> domain = __strdup (++c);
> else
Ok.
> {
> /* The name contains no domain information. Use the name
> now to get more information. */
> while (__gethostname (tmpbuf->data, tmpbuf->length))
> if (!scratch_buffer_grow (tmpbuf))
> return;
Ok.
> if ((c = strchr (tmpbuf->data, '.')) != NULL)
> domain = __strdup (++c);
> else
> {
> /* We need to preserve the hostname. */
> const char *hstname = strdupa (tmpbuf->data);
> while (__gethostbyname_r (hstname, &th,
> tmpbuf->data,
> tmpbuf->length,
> &h, &herror))
> {
> if (herror == NETDB_INTERNAL && errno == ERANGE)
> {
> if (!scratch_buffer_grow (tmpbuf))
> return;
> }
> else
> break;
> }
Ok.
> if (h != NULL && (c = strchr(h->h_name, '.')) != NULL)
> domain = __strdup (++c);
> else
> {
> struct in_addr in_addr;
>
> in_addr.s_addr = htonl (INADDR_LOOPBACK);
>
> while (__gethostbyaddr_r ((const char *) &in_addr,
> sizeof (struct in_addr),
> AF_INET, &th,
> tmpbuf->data,
> tmpbuf->length,
> &h, &herror))
> {
> if (herror == NETDB_INTERNAL && errno == ERANGE)
> {
> if (!scratch_buffer_grow (tmpbuf))
> return;
> }
> else
> break;
> }
Ok.
> if (h != NULL && (c = strchr (h->h_name, '.')) != NULL)
> domain = __strdup (++c);
> }
> }
> }
> }
Ok.
> static char *
> nrl_domainname (void)
> {
> static int not_first;
>
> if (__glibc_likely (atomic_load_acquire (¬_first) != 0))
> return domain;
Multiple threads may have gotten to this point the "first time" (esp if
they get called while the above function is running)...
> __libc_lock_define_initialized (static, lock);
> __libc_lock_lock (lock);
>
> if (atomic_load_relaxed (¬_first) == 0)
> {
... so we test again inside the lock, only one will get the lock *and*
see not_first still zero; ok.
> struct scratch_buffer tmpbuf;
> scratch_buffer_init (&tmpbuf);
>
> nrl_domainname_core (&tmpbuf);
>
> scratch_buffer_free (&tmpbuf);
Calculate the static "domain", ok
> atomic_store_release (¬_first, 1);
Set not_first before releasing lock; Ok.
> }
>
> __libc_lock_unlock (lock);
This is the only exit path, so OK.
> return domain;
> };
Ok.
LGTM
Reviewed-by: DJ Delorie <dj@redhat.com>
next prev parent reply other threads:[~2022-03-08 3:44 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-10 11:07 [PATCH v2 0/3] Fixes for getnameinfo() with NI_NOFQDN Adhemerval Zanella
2021-12-10 11:07 ` [PATCH v2 1/3] inet: Fix getnameinfo (NI_NOFQDN) race condition (BZ#28566) Adhemerval Zanella
2022-02-03 20:52 ` Adhemerval Zanella
2022-03-08 3:44 ` DJ Delorie [this message]
2021-12-10 11:07 ` [PATCH v2 2/3] inet: Remove strdupa from nrl_domainname() Adhemerval Zanella
2022-02-03 20:52 ` Adhemerval Zanella
2022-03-08 3:53 ` DJ Delorie
2021-12-10 11:07 ` [PATCH v2 3/3] inet: Return EAI_MEMORY when nrl_domainname() fails to allocate memory Adhemerval Zanella
2022-02-03 20:53 ` Adhemerval Zanella
2022-03-08 4:12 ` DJ Delorie
2022-03-08 15:43 ` Adhemerval Zanella
-- strict thread matches above, loose matches on Subject: below --
2021-11-12 14:21 [PATCH v2 0/3] Fixes for getnameinfo() with NI_NOFQDN Adhemerval Zanella
2021-11-12 14:21 ` [PATCH v2 1/3] inet: Fix getnameinfo (NI_NOFQDN) race condition (BZ#28566) Adhemerval Zanella
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