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From: Florian Weimer <fweimer@redhat.com>
To: Mingli Yu <Mingli.Yu@windriver.com>
Cc: libc-alpha@sourceware.org
Subject: [PATCH] Linux gethostid: Check for NULL value from gethostbyname_r [BZ #23679]
Date: Wed, 19 Sep 2018 20:52:00 -0000
Message-ID: <87zhwdjjmd.fsf@oldenburg.str.redhat.com>
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X-SW-Source: 2018-09/txt/msg00335.txt.bz2

Compared to the version posted on Bugzilla, I added a check on ret.  If
ret == 0 and hp == NULL, herr and errno are not necessarily valid.

Okay for master?

Thanks,
Florian

Commit message:

Linux gethostid: Check for NULL value from gethostbyname_r [BZ #23679]

A NULL value can happen with certain gethostbyname_r failures.

ChangeLog entry:

2018-09-19  Mingli Yu  <Mingli.Yu@windriver.com>

	* sysdeps/unix/sysv/linux/gethostid.c (gethostid): Check for NULL
	value from gethostbyname_r.

diff --git a/sysdeps/unix/sysv/linux/gethostid.c b/sysdeps/unix/sysv/linux/gethostid.c
index 2e20f034dc..ee0190e7f9 100644
--- a/sysdeps/unix/sysv/linux/gethostid.c
+++ b/sysdeps/unix/sysv/linux/gethostid.c
@@ -102,12 +102,12 @@ gethostid (void)
     {
       int ret = __gethostbyname_r (hostname, &hostbuf,
 				   tmpbuf.data, tmpbuf.length, &hp, &herr);
-      if (ret == 0)
+      if (ret == 0 && hp != NULL)
 	break;
       else
 	{
 	  /* Enlarge the buffer on ERANGE.  */
-	  if (herr == NETDB_INTERNAL && errno == ERANGE)
+	  if (ret != 0 && herr == NETDB_INTERNAL && errno == ERANGE)
 	    {
 	      if (!scratch_buffer_grow (&tmpbuf))
 		return 0;