From: Steven Rostedt <srostedt@redhat.com>
Date: Sat, 13 Mar 2010 00:41:23 +0000 (-0500)
Subject: function-graph: Init curr_ret_stack with ret_stack
X-Git-Tag: v2.6.34-rc2~52^2~3
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ea14eb714041d40fcc5180b5a586034503650149;p=pandora-kernel.git

function-graph: Init curr_ret_stack with ret_stack

If the graph tracer is active, and a task is forked but the allocating of
the processes graph stack fails, it can cause crash later on.

This is due to the temporary stack being NULL, but the curr_ret_stack
variable is copied from the parent. If it is not -1, then in
ftrace_graph_probe_sched_switch() the following:

	for (index = next->curr_ret_stack; index >= 0; index--)
		next->ret_stack[index].calltime += timestamp;

Will cause a kernel OOPS.

Found with Li Zefan's ftrace_stress_test.

Cc: stable@kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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