[glibc] Get new entropy on each attempt __gen_tempname (BZ #15813)

[Adhemerval Zanella <azanella@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=e1df30fbc2e2167a982c0e77a7ebee28f4dd0800

commit e1df30fbc2e2167a982c0e77a7ebee28f4dd0800
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Thu Jul 25 11:22:17 2019 -0300

    Get new entropy on each attempt __gen_tempname (BZ #15813)
    
    This is missing bit for fully fix BZ#15813 (the other two were fixed
    by 359653aaacad463).
    
    Checked on x86_64-linux-gnu.
    
    	[BZ #15813]
    	sysdeps/posix/tempname.c (__gen_tempname): get entrypy on each
    	attempt.

Diff:
---
 ChangeLog                |  6 ++++++
 sysdeps/posix/tempname.c | 13 ++++++-------
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index cdb9e14..17918a1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2019-08-01  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
+
+	[BZ #15813]
+	sysdeps/posix/tempname.c (__gen_tempname): get entropy on each
+	attempt.
+
 2019-08-01  Carlos O'Donell <carlos@redhat.com>
 
 	* version.h (RELEASE): Set to "stable".
diff --git a/sysdeps/posix/tempname.c b/sysdeps/posix/tempname.c
index de34694..310df3c 100644
--- a/sysdeps/posix/tempname.c
+++ b/sysdeps/posix/tempname.c
@@ -186,7 +186,6 @@ __gen_tempname (char *tmpl, int suffixlen, int flags, int kind)
 {
   int len;
   char *XXXXXX;
-  uint64_t value;
   unsigned int count;
   int fd = -1;
   int save_errno = errno;
@@ -218,13 +217,13 @@ __gen_tempname (char *tmpl, int suffixlen, int flags, int kind)
   /* This is where the Xs start.  */
   XXXXXX = &tmpl[len - 6 - suffixlen];
 
-  /* Get some more or less random data.  */
-  RANDOM_BITS (value);
-  value ^= (uint64_t)__getpid () << 32;
-
-  for (count = 0; count < attempts; value += 7777, ++count)
+  uint64_t pid = (uint64_t) __getpid () << 32;
+  for (count = 0; count < attempts; ++count)
     {
-      uint64_t v = value;
+      uint64_t v;
+      /* Get some more or less random data.  */
+      RANDOM_BITS (v);
+      v ^= pid;
 
       /* Fill in the random bits.  */
       XXXXXX[0] = letters[v % 62];