[PATCH 4.16 117/272] tools/thermal: tmon: fix for segfault

Greg Kroah-Hartman
2018-05-28T11:46:17Z

From: Frank Asseg <frank.asseg@objecthunter.net>

[ Upstream commit 6c59f64b7ecf2bccbe73931d7d573d66ed13b537 ]

Fixes a segfault occurring when e.g. <TAB> is pressed multiple times in the
ncurses tmon application. The segfault is caused by incrementing
cur_thermal_record in the main function without checking if it's value reached
NR_THERMAL_RECORD immediately. Since the boundary check only occurred in
update_thermal_data a race condition existed, which lead to an attempted read
beyond the last element of the trec array.

The fix was implemented by moving the cur_thermal_record incrementation to the
update_thermal_data function using a temporary variable on which the boundary
condition is checked before updating cur_thread_record, so that the variable is
never incremented beyond the trec array's boundary.

It seems the segfault does not occur on every machine: On a HP EliteBook G4 the
segfault happens, while it does not happen on a Thinkpad T540p.

Signed-off-by: Frank Asseg <frank.asseg@objecthunter.net>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
tools/thermal/tmon/sysfs.c | 12 +++++++-----
tools/thermal/tmon/tmon.c | 1 -
2 files changed, 7 insertions(+), 6 deletions(-)

--- a/tools/thermal/tmon/sysfs.c
+++ b/tools/thermal/tmon/sysfs.c
@@ -486,6 +486,7 @@ int zone_instance_to_index(int zone_inst
int update_thermal_data()
{
int i;
+ int next_thermal_record = cur_thermal_record + 1;
char tz_name[256];
static unsigned long samples;

@@ -495,9 +496,9 @@ int update_thermal_data()
}

/* circular buffer for keeping historic data */
- if (cur_thermal_record >= NR_THERMAL_RECORDS)
- cur_thermal_record = 0;
- gettimeofday(&trec[cur_thermal_record].tv, NULL);
+ if (next_thermal_record >= NR_THERMAL_RECORDS)
+ next_thermal_record = 0;
+ gettimeofday(&trec[next_thermal_record].tv, NULL);
if (tmon_log) {
fprintf(tmon_log, "%lu ", ++samples);
fprintf(tmon_log, "%3.1f ", p_param.t_target);
@@ -507,11 +508,12 @@ int update_thermal_data()
snprintf(tz_name, 256, "%s/%s%d", THERMAL_SYSFS, TZONE,
ptdata.tzi[i].instance);
sysfs_get_ulong(tz_name, "temp",
- &trec[cur_thermal_record].temp[i]);
+ &trec[next_thermal_record].temp[i]);
if (tmon_log)
fprintf(tmon_log, "%lu ",
- trec[cur_thermal_record].temp[i]/1000);
+ trec[next_thermal_record].temp[i] / 1000);
}
+ cur_thermal_record = next_thermal_record;
for (i = 0; i < ptdata.nr_cooling_dev; i++) {
char cdev_name[256];
unsigned long val;
--- a/tools/thermal/tmon/tmon.c
+++ b/tools/thermal/tmon/tmon.c
@@ -336,7 +336,6 @@ int main(int argc, char **argv)
show_data_w();
show_cooling_device();
}
- cur_thermal_record++;
time_elapsed += ticktime;
controller_handler(trec[0].temp[target_tz_index] / 1000,
&yk);