[PATCH] mx_check_mailbox: prevent dereferencing a null pointer

[Eike Rathke]

This happened when in an IMAP index view the underlying connection was
terminated, ctx->mx_ops was NULL and thus accessing ctx->mx_ops->check
segfaulted.



# HG changeset patch
# User Eike Rathke <er...@erack.de>
# Date 1474491061 -7200
#      Wed Sep 21 22:51:01 2016 +0200
# Node ID 0ac8ddd821764e6cbdebaea0f58bef3d9434040f
# Parent  c41562a8118b8db61d4828287c4158f43c652d2b
mx_check_mailbox: prevent dereferencing a null pointer

This happened when in an IMAP index view the underlying connection was
terminated, ctx->mx_ops was NULL and thus accessing ctx->mx_ops->check
segfaulted.

diff --git a/mx.c b/mx.c
--- a/mx.c
+++ b/mx.c
@@ -1299,6 +1299,12 @@
     return -1;
   }
 
+  if (!ctx->mx_ops)
+  {
+    dprint (1, (debugfile, "mx_check_mailbox: null or invalid context mx_ops.\n"));
+    return -1;
+  }
+
   return ctx->mx_ops->check (ctx, index_hint);
 }
 

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