gdbserver crash in gdb/gdbserver/thread.c::thread_search_callback

Connecting GDB to a LynxOS-178 GDBserver causes GDBserver to crash:

    % gdbserver :4444 simple_main
    Process simple_main created; pid = 19
    Listening on port 4444
    Remote debugging from host 205.232.38.10
    Segmentation fault (core dumped)

The crash happens in thread_search_callback where the function
calls the_target->thread_stopped (via the thread_stopped macro)
without verifying whether the callback is NULL or not.

For the record, the regression was introduced by:

    commit a67a9faef0e32886c83611cc7a0ba61e91123063
    Date:   Mon Nov 30 16:05:26 2015 +0000
    Subject: gdbserver:prepare_access_memory: pick another thread

This patch avoids the crash by checking the value of the callback
first, before calling it.

gdb/gdbserver/ChangeLog:

        * target.c (thread_search_callback): Add check that
        the thread_stopped target callback is not NULL before
        calling it.

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index 1d240f2..a80a088 100644 (file)
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,9 @@
+2015-12-22  Joel Brobecker  <brobecker@adacore.com>
+
+       * target.c (thread_search_callback): Add check that
+       the thread_stopped target callback is not NULL before
+       calling it.
+
 2015-12-21  Yao Qi  <yao.qi@linaro.org>
 
        * linux-aarch32-low.h [__aarch64__]: Use arm_abi_breakpoint

diff --git a/gdb/gdbserver/target.c b/gdb/gdbserver/target.c
index b376ce8..59736e5 100644 (file)
--- a/gdb/gdbserver/target.c
+++ b/gdb/gdbserver/target.c
@@ -68,7 +68,9 @@ thread_search_callback (struct inferior_list_entry *entry, void *args)
   if (ptid_get_pid (entry->id) == ptid_get_pid (s->current_gen_ptid)
       && mythread_alive (ptid_of (thread)))
     {
-      if (s->stopped == NULL && thread_stopped (thread))
+      if (s->stopped == NULL
+         && the_target->thread_stopped != NULL
+         && thread_stopped (thread))
        s->stopped = thread;
 
       if (s->first == NULL)