path: root/kernel
diff options
authorTom Zanussi <tom.zanussi@linux.intel.com>2019-04-18 10:18:50 -0500
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2019-05-21 12:43:49 -0400
commit55267c88c003a3648567beae7c90512d3e2ab15e (patch)
treeae8c81f684088c271cb7a17863b7a816287e27d7 /kernel
parenta188339ca5a396acc588e5851ed7e19f66b0ebd9 (diff)
tracing: Prevent hist_field_var_ref() from accessing NULL tracing_map_elts
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.git.tom.zanussi@linux.intel.com 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>
Diffstat (limited to 'kernel')
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 7fca3457c705..06e7b9f66de6 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1854,6 +1854,9 @@ 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];