[ Upstream commit 55267c88c003a3648567beae7c90512d3e2ab15e ]
hist_field_var_ref() is an implementation of hist_field_fn_t(), which can be called with a null tracing_map_elt elt param when assembling a key in event_hist_trigger().
In the case of hist_field_var_ref() this doesn't make sense, because a variable can only be resolved by looking it up using an already assembled key i.e. a variable can't be used to assemble a key since the key is required in order to access the variable.
Upper layers should prevent the user from constructing a key using a variable in the first place, but in case one slips through, it shouldn't cause a NULL pointer dereference. Also if one does slip through, we want to know about it, so emit a one-time warning in that case.
Link: http://lkml.kernel.org/r/64ec8dc15c14d305295b64cdfcc6b2b9dd14753f.1555597045...
Reported-by: Vincent Bernat vincent@bernat.ch Signed-off-by: Tom Zanussi tom.zanussi@linux.intel.com Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/trace/trace_events_hist.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 0a200d42fa96..f50d57eac875 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -1815,6 +1815,9 @@ static u64 hist_field_var_ref(struct hist_field *hist_field, struct hist_elt_data *elt_data; u64 var_val = 0;
+ if (WARN_ON_ONCE(!elt)) + return var_val; + elt_data = elt->private_data; var_val = elt_data->var_ref_vals[hist_field->var_ref_idx];