4.4-stable review patch. If anyone has any objections, please let me know.
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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);