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authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2016-12-08 20:54:49 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-01-09 08:07:50 +0100
commite945df4c6bc2e3e188e02b199ce1766f557890e5 (patch)
tree945c6b7680e70af9e54d21b7bd86298d40423af6 /kernel
parent88e41441ccd45eb6d2f68b6260a62b8d8e6e0316 (diff)
fgraph: Handle a case where a tracer ignores set_graph_notrace
commit 794de08a16cf1fc1bf785dc48f66d36218cf6d88 upstream. Both the wakeup and irqsoff tracers can use the function graph tracer when the display-graph option is set. The problem is that they ignore the notrace file, and record the entry of functions that would be ignored by the function_graph tracer. This causes the trace->depth to be recorded into the ring buffer. The set_graph_notrace uses a trick by adding a large negative number to the trace->depth when a graph function is to be ignored. On trace output, the graph function uses the depth to record a stack of functions. But since the depth is negative, it accesses the array with a negative number and causes an out of bounds access that can cause a kernel oops or corrupt data. Have the print functions handle cases where a tracer still records functions even when they are in set_graph_notrace. Also add warnings if the depth is below zero before accessing the array. Note, the function graph logic will still prevent the return of these functions from being recorded, which means that they will be left hanging without a return. For example: # echo '*spin*' > set_graph_notrace # echo 1 > options/display-graph # echo wakeup > current_tracer # cat trace [...] _raw_spin_lock() { preempt_count_add() { do_raw_spin_lock() { update_rq_clock(); Where it should look like: _raw_spin_lock() { preempt_count_add(); do_raw_spin_lock(); } update_rq_clock(); Cc: Namhyung Kim <namhyung.kim@lge.com> Fixes: 29ad23b00474 ("ftrace: Add set_graph_notrace filter") Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/trace_functions_graph.c17
1 files changed, 14 insertions, 3 deletions
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index a663cbb84107..7fd6f5a26143 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -780,6 +780,10 @@ print_graph_entry_leaf(struct trace_iterator *iter,
cpu_data = per_cpu_ptr(data->cpu_data, cpu);
+ /* If a graph tracer ignored set_graph_notrace */
+ if (call->depth < -1)
+ call->depth += FTRACE_NOTRACE_DEPTH;
+
/*
* Comments display at + 1 to depth. Since
* this is a leaf function, keep the comments
@@ -788,7 +792,8 @@ print_graph_entry_leaf(struct trace_iterator *iter,
cpu_data->depth = call->depth - 1;
/* No need to keep this function around for this depth */
- if (call->depth < FTRACE_RETFUNC_DEPTH)
+ if (call->depth < FTRACE_RETFUNC_DEPTH &&
+ !WARN_ON_ONCE(call->depth < 0))
cpu_data->enter_funcs[call->depth] = 0;
}
@@ -818,11 +823,16 @@ print_graph_entry_nested(struct trace_iterator *iter,
struct fgraph_cpu_data *cpu_data;
int cpu = iter->cpu;
+ /* If a graph tracer ignored set_graph_notrace */
+ if (call->depth < -1)
+ call->depth += FTRACE_NOTRACE_DEPTH;
+
cpu_data = per_cpu_ptr(data->cpu_data, cpu);
cpu_data->depth = call->depth;
/* Save this function pointer to see if the exit matches */
- if (call->depth < FTRACE_RETFUNC_DEPTH)
+ if (call->depth < FTRACE_RETFUNC_DEPTH &&
+ !WARN_ON_ONCE(call->depth < 0))
cpu_data->enter_funcs[call->depth] = call->func;
}
@@ -1052,7 +1062,8 @@ print_graph_return(struct ftrace_graph_ret *trace, struct trace_seq *s,
*/
cpu_data->depth = trace->depth - 1;
- if (trace->depth < FTRACE_RETFUNC_DEPTH) {
+ if (trace->depth < FTRACE_RETFUNC_DEPTH &&
+ !WARN_ON_ONCE(trace->depth < 0)) {
if (cpu_data->enter_funcs[trace->depth] != trace->func)
func_match = 0;
cpu_data->enter_funcs[trace->depth] = 0;