[PATCH] getpw: Get rid of alloca

[Joe Simmons-Talbott <josimmon@redhat.com>]

Use a scratch_buffer rather than alloca to avoid potential stack
overflow.
---
 pwd/getpw.c | 34 +++++++++++++++++++++++++++-------
 1 file changed, 27 insertions(+), 7 deletions(-)

diff --git a/pwd/getpw.c b/pwd/getpw.c
index cf747374b8..7a27d79910 100644
--- a/pwd/getpw.c
+++ b/pwd/getpw.c
@@ -15,8 +15,8 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <alloca.h>
 #include <errno.h>
+#include <scratch_buffer.h>
 #include <stdio.h>
 #include <unistd.h>
 #include <pwd.h>
@@ -34,28 +34,48 @@ __getpw (__uid_t uid, char *buf)
   size_t buflen;
   char *tmpbuf;
   struct passwd resbuf, *p;
+  int retval = 0;
+  struct scratch_buffer sbuf;
+  scratch_buffer_init (&sbuf);
 
   if (buf == NULL)
     {
       __set_errno (EINVAL);
-      return -1;
+      retval =  -1;
+      goto error_out;
     }
 
   buflen = __sysconf (_SC_GETPW_R_SIZE_MAX);
-  tmpbuf = alloca (buflen);
+  if (!scratch_buffer_set_array_size (&sbuf, 1, buflen))
+    {
+      retval = -1;
+      goto error_out;
+    }
+  tmpbuf = sbuf.data;
 
   if (__getpwuid_r (uid, &resbuf, tmpbuf, buflen, &p) != 0)
-    return -1;
+    {
+      retval = -1;
+      goto error_out;
+    }
 
   if (p == NULL)
-    return -1;
+    {
+      retval = -1;
+      goto error_out;
+    }
 
   if (sprintf (buf, "%s:%s:%lu:%lu:%s:%s:%s", p->pw_name, p->pw_passwd,
 	       (unsigned long int) p->pw_uid, (unsigned long int) p->pw_gid,
 	       p->pw_gecos, p->pw_dir, p->pw_shell) < 0)
-    return -1;
+    {
+      retval = -1;
+      goto error_out;
+    }
 
-  return 0;
+error_out:
+  scratch_buffer_free (&sbuf);
+  return retval;
 }
 weak_alias (__getpw, getpw)
 
-- 
2.39.2