gethostid (Linux variant): Switch to struct scratch_buffer [BZ #18023]
Commit Message
On 06/26/2018 06:58 PM, Adhemerval Zanella wrote:
>> + /* Determine the IP address of the host name. */
>> + struct scratch_buffer tmpbuf;
>> + scratch_buffer_init (&tmpbuf);
>> + while (true)
>> + {
>> + int ret = __gethostbyname_r (hostname, &hostbuf,
>> + tmpbuf.data, tmpbuf.length, &hp, &herr);
>> + if (ret == 0)
>> + break;
>> + else
>> + {
>> + /* Enlarge the buffer on ERANGE. */
>> + if (herr == NETDB_INTERNAL && errno == ERANGE)
>> + {
>> + if (!scratch_buffer_grow (&tmpbuf))
>> + return 0;
>> + }
>> + else
>> + /* Other errors are a failure. Return an arbitrary value. */
> Shouldn' it call 'scratch_buffer_free' here for the case the buffer is
> grown and a subsequent __gethostbyname_r results something different
> than ERANGE (assuming it is possible)?
Thanks, you are right. New patch attached.
Florian
Comments
On 26/06/2018 14:33, Florian Weimer wrote:
> On 06/26/2018 06:58 PM, Adhemerval Zanella wrote:
>>> + /* Determine the IP address of the host name. */
>>> + struct scratch_buffer tmpbuf;
>>> + scratch_buffer_init (&tmpbuf);
>>> + while (true)
>>> + {
>>> + int ret = __gethostbyname_r (hostname, &hostbuf,
>>> + tmpbuf.data, tmpbuf.length, &hp, &herr);
>>> + if (ret == 0)
>>> + break;
>>> + else
>>> + {
>>> + /* Enlarge the buffer on ERANGE. */
>>> + if (herr == NETDB_INTERNAL && errno == ERANGE)
>>> + {
>>> + if (!scratch_buffer_grow (&tmpbuf))
>>> + return 0;
>>> + }
>>> + else
>>> + /* Other errors are a failure. Return an arbitrary value. */
>> Shouldn' it call 'scratch_buffer_free' here for the case the buffer is
>> grown and a subsequent __gethostbyname_r results something different
>> than ERANGE (assuming it is possible)?
>
> Thanks, you are right. New patch attached.
>
> Florian
New version LGTM, thanks.
On Jun 26 2018, Florian Weimer <fweimer@redhat.com> wrote:
> @@ -88,29 +88,43 @@ gethostid (void)
> return id;
> }
>
> - /* Getting from the file was not successful. An intelligent guess for
> - a unique number of a host is its IP address. Return this. */
> + /* Getting from the file was not successful. An intelligent guess
> + for a unique number of a host is its IP address. To get the IP
> + address we need to know the host name. */
> if (__gethostname (hostname, MAXHOSTNAMELEN) < 0 || hostname[0] == '\0')
> /* This also fails. Return and arbitrary value. */
> return 0;
>
> - buflen = 1024;
> - buffer = __alloca (buflen);
> -
> - /* To get the IP address we need to know the host name. */
> - while (__gethostbyname_r (hostname, &hostbuf, buffer, buflen, &hp, &herr)
> - != 0
> - || hp == NULL)
> - if (herr != NETDB_INTERNAL || errno != ERANGE)
> - return 0;
> - else
> - /* Enlarge buffer. */
> - buffer = extend_alloca (buffer, buflen, 2 * buflen);
> + /* Determine the IP address of the host name. */
> + struct scratch_buffer tmpbuf;
> + scratch_buffer_init (&tmpbuf);
> + while (true)
> + {
> + int ret = __gethostbyname_r (hostname, &hostbuf,
> + tmpbuf.data, tmpbuf.length, &hp, &herr);
> + if (ret == 0)
> + break;
That fails to handle hp == NULL any more, see bug 23679.
Andreas.
* Andreas Schwab:
> On Jun 26 2018, Florian Weimer <fweimer@redhat.com> wrote:
>
>> @@ -88,29 +88,43 @@ gethostid (void)
>> return id;
>> }
>>
>> - /* Getting from the file was not successful. An intelligent guess for
>> - a unique number of a host is its IP address. Return this. */
>> + /* Getting from the file was not successful. An intelligent guess
>> + for a unique number of a host is its IP address. To get the IP
>> + address we need to know the host name. */
>> if (__gethostname (hostname, MAXHOSTNAMELEN) < 0 || hostname[0] == '\0')
>> /* This also fails. Return and arbitrary value. */
>> return 0;
>>
>> - buflen = 1024;
>> - buffer = __alloca (buflen);
>> -
>> - /* To get the IP address we need to know the host name. */
>> - while (__gethostbyname_r (hostname, &hostbuf, buffer, buflen, &hp, &herr)
>> - != 0
>> - || hp == NULL)
>> - if (herr != NETDB_INTERNAL || errno != ERANGE)
>> - return 0;
>> - else
>> - /* Enlarge buffer. */
>> - buffer = extend_alloca (buffer, buflen, 2 * buflen);
>> + /* Determine the IP address of the host name. */
>> + struct scratch_buffer tmpbuf;
>> + scratch_buffer_init (&tmpbuf);
>> + while (true)
>> + {
>> + int ret = __gethostbyname_r (hostname, &hostbuf,
>> + tmpbuf.data, tmpbuf.length, &hp, &herr);
>> + if (ret == 0)
>> + break;
>
> That fails to handle hp == NULL any more, see bug 23679.
Oops. Do you want me to write a patch?
On Sep 18 2018, Florian Weimer <fw@deneb.enyo.de> wrote:
> Oops. Do you want me to write a patch?
There is one attached to the bug.
Andreas.
* Andreas Schwab:
> On Sep 18 2018, Florian Weimer <fw@deneb.enyo.de> wrote:
>
>> Oops. Do you want me to write a patch?
>
> There is one attached to the bug.
Right, I'll take care of it.
Subject: [PATCH] gethostid (Linux variant): Switch to struct scratch_buffer [BZ #18023]
To: libc-alpha@sourceware.org
Previously, extend_alloca was used without alloca accounting,
which could have been problematic with large NSS results.
2018-06-26 Florian Weimer <fweimer@redhat.com>
[BZ #18023]
* sysdeps/unix/sysv/linux/gethostid.c (gethostid): Use struct
scratch_buffer instead of extend_alloca. Update comments.
@@ -21,6 +21,7 @@
#include <unistd.h>
#include <netdb.h>
#include <not-cancel.h>
+#include <stdbool.h>
#define HOSTIDFILE "/etc/hostid"
@@ -63,13 +64,12 @@ sethostid (long int id)
# include <sys/param.h>
# include <resolv/netdb.h>
# include <netinet/in.h>
+# include <scratch_buffer.h>
long int
gethostid (void)
{
char hostname[MAXHOSTNAMELEN + 1];
- size_t buflen;
- char *buffer;
struct hostent hostbuf, *hp;
int32_t id;
struct in_addr in;
@@ -88,29 +88,43 @@ gethostid (void)
return id;
}
- /* Getting from the file was not successful. An intelligent guess for
- a unique number of a host is its IP address. Return this. */
+ /* Getting from the file was not successful. An intelligent guess
+ for a unique number of a host is its IP address. To get the IP
+ address we need to know the host name. */
if (__gethostname (hostname, MAXHOSTNAMELEN) < 0 || hostname[0] == '\0')
/* This also fails. Return and arbitrary value. */
return 0;
- buflen = 1024;
- buffer = __alloca (buflen);
-
- /* To get the IP address we need to know the host name. */
- while (__gethostbyname_r (hostname, &hostbuf, buffer, buflen, &hp, &herr)
- != 0
- || hp == NULL)
- if (herr != NETDB_INTERNAL || errno != ERANGE)
- return 0;
- else
- /* Enlarge buffer. */
- buffer = extend_alloca (buffer, buflen, 2 * buflen);
+ /* Determine the IP address of the host name. */
+ struct scratch_buffer tmpbuf;
+ scratch_buffer_init (&tmpbuf);
+ while (true)
+ {
+ int ret = __gethostbyname_r (hostname, &hostbuf,
+ tmpbuf.data, tmpbuf.length, &hp, &herr);
+ if (ret == 0)
+ break;
+ else
+ {
+ /* Enlarge the buffer on ERANGE. */
+ if (herr == NETDB_INTERNAL && errno == ERANGE)
+ {
+ if (!scratch_buffer_grow (&tmpbuf))
+ return 0;
+ }
+ /* Other errors are a failure. Return an arbitrary value. */
+ else
+ {
+ scratch_buffer_free (&tmpbuf);
+ return 0;
+ }
+ }
+ }
in.s_addr = 0;
memcpy (&in, hp->h_addr,
(int) sizeof (in) < hp->h_length ? (int) sizeof (in) : hp->h_length);
-
+ scratch_buffer_free (&tmpbuf);
/* For the return value to be not exactly the IP address we do some
bit fiddling. */
return (int32_t) (in.s_addr << 16 | in.s_addr >> 16);