From 6c59f64b7ecf2bccbe73931d7d573d66ed13b537 Mon Sep 17 00:00:00 2001 From: Frank Asseg Date: Mon, 12 Mar 2018 19:57:06 +0100 Subject: tools/thermal: tmon: fix for segfault Fixes a segfault occurring when e.g. 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 Signed-off-by: Jiri Kosina --- tools/thermal/tmon/sysfs.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) (limited to 'tools/thermal/tmon/sysfs.c') diff --git a/tools/thermal/tmon/sysfs.c b/tools/thermal/tmon/sysfs.c index 1c12536f2081..18f523557983 100644 --- 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; -- cgit v1.2.3