Merged revisions 375362 via svnmerge from

file:///srv/subversion/repos/asterisk/branches/10

................
  r375362 | rmudgett | 2012-10-29 10:51:24 -0500 (Mon, 29 Oct 2012) | 15 lines

  chan_dahdi: Fix segfault dereferencing a NULL tech_pvt.

  The tech support customer was using the AMI Redirect action shortly after
  a call was placed.  While the channel tried to do an ast_read(), the
  masquerade resulting from the channel redirect took place.  The masquerade
  in the middle of the ast_read() resulted in the segfault.

  (closes issue AST-1025)
  Reported by: Trey Blancher
  Patches:
        jira_ast_1025_v1.8_v2.patch (license #5621) patch uploaded by rmudgett
  ........

  Merged revisions 375361 from http://svn.asterisk.org/svn/asterisk/branches/1.8
................

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10-digiumphones@375387 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/channels/chan_dahdi.c b/channels/chan_dahdi.c
index 04b173ed3e4e1bb47df2e4fc3f528d5268b6cc0e..ebf4eb7ddaa468a68cd6eb4bc4c8aa5a14937115 100644 (file)
--- a/channels/chan_dahdi.c
+++ b/channels/chan_dahdi.c
@@ -9014,11 +9014,20 @@ static struct ast_frame *dahdi_read(struct ast_channel *ast)
                CHANNEL_DEADLOCK_AVOIDANCE(ast);
 
                /*
-                * For PRI channels, we must refresh the private pointer because
-                * the call could move to another B channel while the Asterisk
-                * channel is unlocked.
+                * Check to see if the channel is still associated with the same
+                * private structure.  While the Asterisk channel was unlocked
+                * the following events may have occured:
+                *
+                * 1) A masquerade may have associated the channel with another
+                * technology or private structure.
+                *
+                * 2) For PRI calls, call signaling could change the channel
+                * association to another B channel (private structure).
                 */
-               p = ast->tech_pvt;
+               if (ast->tech_pvt != p) {
+                       /* The channel is no longer associated.  Quit gracefully. */
+                       return &ast_null_frame;
+               }
        }
 
        idx = dahdi_get_index(ast, p, 0);