[linux-pam] Make pam_tty_audit work with old kernels not supporting log_passwd.

[Tomáš Mráz]

commit 7d0a74fbab4e413dd115592962e1ae68adbe9e2c
Author: Tomas Mraz <tmraz(a)fedoraproject.org&gt;
Date:   Mon Oct 14 14:04:23 2013 +0200

    Make pam_tty_audit work with old kernels not supporting log_passwd.
    
    modules/pam_tty_audit/pam_tty_audit.c(nl_recv): Pad result with zeros
    if message is short from older kernel.
    
    Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com&gt;

 modules/pam_tty_audit/pam_tty_audit.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)
---
diff --git a/modules/pam_tty_audit/pam_tty_audit.c
b/modules/pam_tty_audit/pam_tty_audit.c
index cc86255..b6f53be 100644
--- a/modules/pam_tty_audit/pam_tty_audit.c
+++ b/modules/pam_tty_audit/pam_tty_audit.c
@@ -109,7 +109,7 @@ nl_recv (int fd, unsigned type, void *buf, size_t size)
   struct msghdr msg;
   struct nlmsghdr nlm;
   struct iovec iov[2];
-  ssize_t res;
+  ssize_t res, resdiff;
 
  again:
   iov[0].iov_base = &nlm;
@@ -161,12 +161,17 @@ nl_recv (int fd, unsigned type, void *buf, size_t size)
   res = recvmsg (fd, &msg, 0);
   if (res == -1)
     return -1;
-  if ((size_t)res != NLMSG_LENGTH (size)
+  resdiff = NLMSG_LENGTH(size) - (size_t)res;
+  if (resdiff < 0
       || nlm.nlmsg_type != type)
     {
       errno = EIO;
       return -1;
     }
+  else if (resdiff > 0)
+    {
+      memset((char *)buf + size - resdiff, 0, resdiff);
+    }
   return 0;
 }