From: DJ Delorie <dj@redhat.com>
To: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Cc: libc-alpha@sourceware.org
Subject: Re: [PATCH v2 3/3] inet: Return EAI_MEMORY when nrl_domainname() fails to allocate memory
Date: Mon, 07 Mar 2022 23:12:26 -0500 [thread overview]
Message-ID: <xnk0d55bh1.fsf@greed.delorie.com> (raw)
In-Reply-To: <20211210110733.1499984-4-adhemerval.zanella@linaro.org> (message from Adhemerval Zanella via Libc-alpha on Fri, 10 Dec 2021 08:07:33 -0300)
Adhemerval Zanella via Libc-alpha <libc-alpha@sourceware.org> writes:
> -static void
> +static bool
Ok. Please include comment saying what true/false return means, though.
> nrl_domainname_core (struct scratch_buffer *tmpbuf)
> {
> char *c;
> struct hostent *h, th;
> int herror;
>
> - while (__gethostbyname_r ("localhost", &th,
> - tmpbuf->data, tmpbuf->length,
> + while (__gethostbyname_r ("localhost", &th, tmpbuf->data, tmpbuf->length,
Formatting; ok
> if (!scratch_buffer_grow (tmpbuf))
> - return;
> + return false;
Ok.
> else
> break;
> }
>
> if (h != NULL && (c = strchr (h->h_name, '.')) != NULL)
> - domain = __strdup (++c);
> - else
> {
> + domain = __strdup (++c);
> + return domain != NULL;
> + }
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;
> + /* 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 false;
Ok.
> -
> - if ((c = strchr (tmpbuf->data, '.')) != NULL)
> - domain = __strdup (++c);
> + if ((c = strchr (tmpbuf->data, '.')) != NULL)
> + {
> + domain = __strdup (++c);
> + return domain != NULL;
> + }
Ok.
> - else
> - {
> - /* We need to preserve the hostname. */
> - size_t hstnamelen = strlen (tmpbuf->data) + 1;
> - while (__gethostbyname_r (tmpbuf->data, &th,
> - tmpbuf->data + hstnamelen,
> - tmpbuf->length - hstnamelen,
> - &h, &herror))
> - {
> - if (herror == NETDB_INTERNAL && errno == ERANGE)
> - {
> - if (!scratch_buffer_grow_preserve (tmpbuf))
> - return;
> - }
> - else
> - break;
> - }
>
> + /* We need to preserve the hostname. */
> + size_t hstnamelen = strlen (tmpbuf->data) + 1;
> + while (__gethostbyname_r (tmpbuf->data, &th, tmpbuf->data + hstnamelen,
> + tmpbuf->length - hstnamelen, &h, &herror))
> + {
> + if (herror == NETDB_INTERNAL && errno == ERANGE)
> + {
> + if (!scratch_buffer_grow_preserve (tmpbuf))
> + return false;
> + }
> + else
> + break;
> + }
Ok.
> - if (h != NULL && (c = strchr(h->h_name, '.')) != NULL)
> - domain = __strdup (++c);
> + if (h != NULL && (c = strchr(h->h_name, '.')) != NULL)
> + {
> + domain = __strdup (++c);
> + return domain != NULL;
> + }
Ok.
> - 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;
> - }
>
> - if (h != NULL && (c = strchr (h->h_name, '.')) != NULL)
> - domain = __strdup (++c);
> - }
> +
> + struct 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 false;
> }
> + else
> + break;
> + }
> +
> + if (h != NULL && (c = strchr (h->h_name, '.')) != NULL)
> + {
> + domain = __strdup (++c);
> + return domain != NULL;
> }
> + return true;
> }
Ok.
> -static char *
> +static bool
> nrl_domainname (void)
> {
> static int not_first;
>
> if (__glibc_likely (atomic_load_acquire (¬_first) != 0))
> - return domain;
> + return true;
If we successfully ran before, shortcut to success again.
> +
> + int r = true;
Assume we'll succeed again, if more than one thread gets here.
> __libc_lock_define_initialized (static, lock);
> __libc_lock_lock (lock);
> @@ -180,16 +181,15 @@ nrl_domainname (void)
> struct scratch_buffer tmpbuf;
> scratch_buffer_init (&tmpbuf);
>
> - nrl_domainname_core (&tmpbuf);
> + if ((r = nrl_domainname_core (&tmpbuf)))
> + atomic_store_release (¬_first, 1);
If the call is successful, we set not_first to enable the above
shortcut, and set r, which we return.
I note that a failing first time through will not set not_first, so
other threads contending for this lock will also call this block, and
continue calling this block, until they succeed. Therefor the above
shortcut's assumption is valid.
Ok.
> scratch_buffer_free (&tmpbuf);
> -
> - atomic_store_release (¬_first, 1);
> }
>
> __libc_lock_unlock (lock);
>
> - return domain;
> + return r;
This will be TRUE if we skip the block because a previous thread
succeeded, or FALSE if we ran the block and failed.
> };
Ok.
> /* Copy a string to a destination buffer with length checking. Return
> @@ -285,13 +285,17 @@ gni_host_inet_name (struct scratch_buffer *tmpbuf,
>
> if (h)
> {
> - char *c;
> - if ((flags & NI_NOFQDN)
> - && (c = nrl_domainname ())
> - && (c = strstr (h->h_name, c))
> - && (c != h->h_name) && (*(--c) == '.'))
> - /* Terminate the string after the prefix. */
> - *c = '\0';
> + if (flags & NI_NOFQDN)
> + {
> + if (!nrl_domainname ())
> + return EAI_MEMORY;
Same as first line in above logic; ok.
> + char *c = domain;
> + if (c != NULL && (c = strstr (h->h_name, c))
> + && (c != h->h_name) && (*(--c) == '.'))
Matches remainder of the logic. Ok.
> + /* Terminate the string after the prefix. */
> + *c = '\0';
> + }
Ok.
LGTM with that one comment added.
Reviewed-by: DJ Delorie <dj@redhat.com>
next prev parent reply other threads:[~2022-03-08 4:12 UTC|newest]
Thread overview: 13+ 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
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 [this message]
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 3/3] inet: Return EAI_MEMORY when nrl_domainname() fails to allocate memory Adhemerval Zanella
2021-11-12 15:44 ` Andreas Schwab
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