[PATCH 5.4 042/100] tracing/histogram: Do not copy the fixed-size char array field over the field size

Greg Kroah-Hartman
2021-11-24T13:23:47Z

From: Masami Hiramatsu <mhiramat@kernel.org>

[ Upstream commit 63f84ae6b82bb4dff672f76f30c6fd7b9d3766bc ]

Do not copy the fixed-size char array field of the events over
the field size. The histogram treats char array as a string and
there are 2 types of char array in the event, fixed-size and
dynamic string. The dynamic string (__data_loc) field must be
null terminated, but the fixed-size char array field may not
be null terminated (not a string, but just a data).
In that case, histogram can copy the data after the field.
This uses the original field size for fixed-size char array
field to restrict the histogram not to access over the original
field size.

Link: https://lkml.kernel.org/r/163673292822.195747.3696966210526410250.stgit@devnote2

Fixes: 02205a6752f2 (tracing: Add support for 'field variables')
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/trace/trace_events_hist.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 9a73c187d241e..8b33a3c872750 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -2590,9 +2590,10 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
if (!hist_field->type)
goto free;

- if (field->filter_type == FILTER_STATIC_STRING)
+ if (field->filter_type == FILTER_STATIC_STRING) {
hist_field->fn = hist_field_string;
- else if (field->filter_type == FILTER_DYN_STRING)
+ hist_field->size = field->size;
+ } else if (field->filter_type == FILTER_DYN_STRING)
hist_field->fn = hist_field_dynstring;
else
hist_field->fn = hist_field_pstring;
@@ -3530,7 +3531,7 @@ static inline void __update_field_vars(struct tracing_map_elt *elt,
char *str = elt_data->field_var_str[j++];
char *val_str = (char *)(uintptr_t)var_val;

- strscpy(str, val_str, STR_VAR_LEN_MAX);
+ strscpy(str, val_str, val->size);
var_val = (u64)(uintptr_t)str;
}
tracing_map_set_var(elt, var_idx, var_val);
@@ -5359,7 +5360,7 @@ static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,

str = elt_data->field_var_str[idx];
val_str = (char *)(uintptr_t)hist_val;
- strscpy(str, val_str, STR_VAR_LEN_MAX);
+ strscpy(str, val_str, hist_field->size);

hist_val = (u64)(uintptr_t)str;
}
--
2.33.0