Author: mmacy
Date: Sun Jul 22 20:02:14 2018
New Revision: 336616
URL: https://svnweb.freebsd.org/changeset/base/336616

Log:
  Fix a potential use after free in getsockopt() access to inp_options
  
  Discussed with: jhb
  Reviewed by:  sbruno, transport
  MFC after:    2 weeks
  Sponsored by: Limelight Networks
  Differential Revision:        https://reviews.freebsd.org/D14621

Modified:
  head/sys/netinet/ip_output.c

Modified: head/sys/netinet/ip_output.c
==============================================================================
--- head/sys/netinet/ip_output.c        Sun Jul 22 18:31:15 2018        
(r336615)
+++ head/sys/netinet/ip_output.c        Sun Jul 22 20:02:14 2018        
(r336616)
@@ -1256,13 +1256,23 @@ ip_ctloutput(struct socket *so, struct sockopt *sopt)
                switch (sopt->sopt_name) {
                case IP_OPTIONS:
                case IP_RETOPTS:
-                       if (inp->inp_options)
-                               error = sooptcopyout(sopt,
-                                                    mtod(inp->inp_options,
-                                                         char *),
-                                                    inp->inp_options->m_len);
-                       else
+                       INP_RLOCK(inp);
+                       if (inp->inp_options) {
+                               struct mbuf *options;
+
+                               options = m_dup(inp->inp_options, M_NOWAIT);
+                               INP_RUNLOCK(inp);
+                               if (options != NULL) {
+                                       error = sooptcopyout(sopt,
+                                                            mtod(options, char 
*),
+                                                            options->m_len);
+                                       m_freem(options);
+                               } else
+                                       error = ENOMEM;
+                       } else {
+                               INP_RUNLOCK(inp);
                                sopt->sopt_valsize = 0;
+                       }
                        break;
 
                case IP_TOS:
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