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fb43722c SL |
1 | From 2c12c95ac8d163b2f5d8e74a65a7b29f3ed81bd5 Mon Sep 17 00:00:00 2001 |
2 | From: Tom Zanussi <tom.zanussi@linux.intel.com> | |
3 | Date: Thu, 18 Apr 2019 10:18:50 -0500 | |
4 | Subject: tracing: Prevent hist_field_var_ref() from accessing NULL | |
5 | tracing_map_elts | |
6 | ||
7 | [ Upstream commit 55267c88c003a3648567beae7c90512d3e2ab15e ] | |
8 | ||
9 | hist_field_var_ref() is an implementation of hist_field_fn_t(), which | |
10 | can be called with a null tracing_map_elt elt param when assembling a | |
11 | key in event_hist_trigger(). | |
12 | ||
13 | In the case of hist_field_var_ref() this doesn't make sense, because a | |
14 | variable can only be resolved by looking it up using an already | |
15 | assembled key i.e. a variable can't be used to assemble a key since | |
16 | the key is required in order to access the variable. | |
17 | ||
18 | Upper layers should prevent the user from constructing a key using a | |
19 | variable in the first place, but in case one slips through, it | |
20 | shouldn't cause a NULL pointer dereference. Also if one does slip | |
21 | through, we want to know about it, so emit a one-time warning in that | |
22 | case. | |
23 | ||
24 | Link: http://lkml.kernel.org/r/64ec8dc15c14d305295b64cdfcc6b2b9dd14753f.1555597045.git.tom.zanussi@linux.intel.com | |
25 | ||
26 | Reported-by: Vincent Bernat <vincent@bernat.ch> | |
27 | Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com> | |
28 | Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> | |
29 | Signed-off-by: Sasha Levin <sashal@kernel.org> | |
30 | --- | |
31 | kernel/trace/trace_events_hist.c | 3 +++ | |
32 | 1 file changed, 3 insertions(+) | |
33 | ||
34 | diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c | |
35 | index 0a200d42fa96..f50d57eac875 100644 | |
36 | --- a/kernel/trace/trace_events_hist.c | |
37 | +++ b/kernel/trace/trace_events_hist.c | |
38 | @@ -1815,6 +1815,9 @@ static u64 hist_field_var_ref(struct hist_field *hist_field, | |
39 | struct hist_elt_data *elt_data; | |
40 | u64 var_val = 0; | |
41 | ||
42 | + if (WARN_ON_ONCE(!elt)) | |
43 | + return var_val; | |
44 | + | |
45 | elt_data = elt->private_data; | |
46 | var_val = elt_data->var_ref_vals[hist_field->var_ref_idx]; | |
47 | ||
48 | -- | |
49 | 2.20.1 | |
50 |