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

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?


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  <>

	* 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.length, &hp, &herr);
-      if (ret == 0)
+      if (ret == 0 && hp != NULL)
 	  /* 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;

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