diff options
| author | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2017-08-17 16:37:25 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-08-30 10:21:50 +0200 |
| commit | 741397d16a3d65e1629e9be75f5d64687d767664 (patch) | |
| tree | 9e083e5df349b67965e1041268b3c6f4ad9fae40 | |
| parent | fd8235e721ef8bb15ba390d9f2f806f794368536 (diff) | |
ftrace: Check for null ret_stack on profile function graph entry function
commit a8f0f9e49956a74718874b800251455680085600 upstream.
There's a small race when function graph shutsdown and the calling of the
registered function graph entry callback. The callback must not reference
the task's ret_stack without first checking that it is not NULL. Note, when
a ret_stack is allocated for a task, it stays allocated until the task exits.
The problem here, is that function_graph is shutdown, and a new task was
created, which doesn't have its ret_stack allocated. But since some of the
functions are still being traced, the callbacks can still be called.
The normal function_graph code handles this, but starting with commit
8861dd303c ("ftrace: Access ret_stack->subtime only in the function
profiler") the profiler code references the ret_stack on function entry, but
doesn't check if it is NULL first.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=196611
Fixes: 8861dd303c ("ftrace: Access ret_stack->subtime only in the function profiler")
Reported-by: lilydjwg@gmail.com
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | kernel/trace/ftrace.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 4f7ea8446bb5..6e432ed7d0fe 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -876,6 +876,10 @@ static int profile_graph_entry(struct ftrace_graph_ent *trace) function_profile_call(trace->func, 0, NULL, NULL); + /* If function graph is shutting down, ret_stack can be NULL */ + if (!current->ret_stack) + return 0; + if (index >= 0 && index < FTRACE_RETFUNC_DEPTH) current->ret_stack[index].subtime = 0; |