From 6d7aa2b531088c3a277911534179975eb2622954 Mon Sep 17 00:00:00 2001
From: Florian Weimer <fweimer@redhat.com>
Date: Wed, 24 Jan 2018 15:40:29 -0200
Subject: [PATCH] getlogin_r: switch Linux variant to struct scratch_buffer

	[BZ #18023]
	* sysdeps/unix/sysv/linux/getlogin_r.c (__getlogin_r_loginuid):
	Use scratch_buffer instead of extend_alloca.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
---
 ChangeLog                            |  6 +++++
 sysdeps/unix/sysv/linux/getlogin_r.c | 34 +++++++++++-----------------
 2 files changed, 19 insertions(+), 21 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index e6e29b1e11..a30eeead7e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2018-02-06  Florian Weimer <fweimer@redhat.com>
+
+	[BZ #18023]
+	* sysdeps/unix/sysv/linux/getlogin_r.c (__getlogin_r_loginuid):
+	Use scratch_buffer instead of extend_alloca.
+
 2018-02-06  Zack Weinberg  <zackw@panix.com>
 
 	* libio/stdio.h: Don't define getc or putc as macros.
diff --git a/sysdeps/unix/sysv/linux/getlogin_r.c b/sysdeps/unix/sysv/linux/getlogin_r.c
index 84c51d0ecd..73ea14c8f9 100644
--- a/sysdeps/unix/sysv/linux/getlogin_r.c
+++ b/sysdeps/unix/sysv/linux/getlogin_r.c
@@ -18,6 +18,7 @@
 #include <pwd.h>
 #include <unistd.h>
 #include <not-cancel.h>
+#include <scratch_buffer.h>
 
 #define STATIC static
 static int getlogin_r_fd0 (char *name, size_t namesize);
@@ -54,29 +55,22 @@ __getlogin_r_loginuid (char *name, size_t namesize)
 	  endp == uidbuf || *endp != '\0'))
     return -1;
 
-  size_t buflen = 1024;
-  char *buf = alloca (buflen);
-  bool use_malloc = false;
   struct passwd pwd;
   struct passwd *tpwd;
   int result = 0;
   int res;
+  struct scratch_buffer tmpbuf;
+  scratch_buffer_init (&tmpbuf);
 
-  while ((res = __getpwuid_r (uid, &pwd, buf, buflen, &tpwd)) == ERANGE)
-    if (__libc_use_alloca (2 * buflen))
-      buf = extend_alloca (buf, buflen, 2 * buflen);
-    else
-      {
-	buflen *= 2;
-	char *newp = realloc (use_malloc ? buf : NULL, buflen);
-	if (newp == NULL)
-	  {
-	    result = ENOMEM;
-	    goto out;
-	  }
-	buf = newp;
-	use_malloc = true;
-      }
+  while ((res =  __getpwuid_r (uid, &pwd,
+			       tmpbuf.data, tmpbuf.length, &tpwd)) == ERANGE)
+    {
+      if (!scratch_buffer_grow (&tmpbuf))
+	{
+	  result = ENOMEM;
+	  goto out;
+	}
+    }
 
   if (res != 0 || tpwd == NULL)
     {
@@ -95,9 +89,7 @@ __getlogin_r_loginuid (char *name, size_t namesize)
   memcpy (name, pwd.pw_name, needed);
 
  out:
-  if (use_malloc)
-    free (buf);
-
+  scratch_buffer_free (&tmpbuf);
   return result;
 }