6.8-stable review patch. If anyone has any objections, please let me know.
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From: Rafael J. Wysocki rafael.j.wysocki@intel.com
[ Upstream commit c7f7c37271787a7f77d7eedc132b0b419a76b4c8 ]
With the current thermal zone locking arrangement in the debugfs code, user space can open the "mitigations" file for a thermal zone before the zone's debugfs pointer is set which will result in a NULL pointer dereference in tze_seq_start().
Moreover, thermal_debug_tz_remove() is not called under the thermal zone lock, so it can run in parallel with the other functions accessing the thermal zone's struct thermal_debugfs object. Then, it may clear tz->debugfs after one of those functions has checked it and the struct thermal_debugfs object may be freed prematurely.
To address the first problem, pass a pointer to the thermal zone's struct thermal_debugfs object to debugfs_create_file() in thermal_debug_tz_add() and make tze_seq_start(), tze_seq_next(), tze_seq_stop(), and tze_seq_show() retrieve it from s->private instead of a pointer to the thermal zone object. This will ensure that tz_debugfs will be valid across the "mitigations" file accesses until thermal_debugfs_remove_id() called by thermal_debug_tz_remove() removes that file.
To address the second problem, use tz->lock in thermal_debug_tz_remove() around the tz->debugfs value check (in case the same thermal zone is removed at the same time in two different threads) and its reset to NULL.
Fixes: 7ef01f228c9f ("thermal/debugfs: Add thermal debugfs information for mitigation episodes") Cc :6.8+ stable@vger.kernel.org # 6.8+ Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Reviewed-by: Lukasz Luba lukasz.luba@arm.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/thermal/thermal_debugfs.c | 34 ++++++++++++++++++++----------- 1 file changed, 22 insertions(+), 12 deletions(-)
diff --git a/drivers/thermal/thermal_debugfs.c b/drivers/thermal/thermal_debugfs.c index 8d66b3a96be1a..1fe2914a8853b 100644 --- a/drivers/thermal/thermal_debugfs.c +++ b/drivers/thermal/thermal_debugfs.c @@ -139,11 +139,13 @@ struct tz_episode { * we keep track of the current position in the history array. * * @tz_episodes: a list of thermal mitigation episodes + * @tz: thermal zone this object belongs to * @trips_crossed: an array of trip points crossed by id * @nr_trips: the number of trip points currently being crossed */ struct tz_debugfs { struct list_head tz_episodes; + struct thermal_zone_device *tz; int *trips_crossed; int nr_trips; }; @@ -716,8 +718,7 @@ void thermal_debug_update_temp(struct thermal_zone_device *tz)
static void *tze_seq_start(struct seq_file *s, loff_t *pos) { - struct thermal_zone_device *tz = s->private; - struct thermal_debugfs *thermal_dbg = tz->debugfs; + struct thermal_debugfs *thermal_dbg = s->private; struct tz_debugfs *tz_dbg = &thermal_dbg->tz_dbg;
mutex_lock(&thermal_dbg->lock); @@ -727,8 +728,7 @@ static void *tze_seq_start(struct seq_file *s, loff_t *pos)
static void *tze_seq_next(struct seq_file *s, void *v, loff_t *pos) { - struct thermal_zone_device *tz = s->private; - struct thermal_debugfs *thermal_dbg = tz->debugfs; + struct thermal_debugfs *thermal_dbg = s->private; struct tz_debugfs *tz_dbg = &thermal_dbg->tz_dbg;
return seq_list_next(v, &tz_dbg->tz_episodes, pos); @@ -736,15 +736,15 @@ static void *tze_seq_next(struct seq_file *s, void *v, loff_t *pos)
static void tze_seq_stop(struct seq_file *s, void *v) { - struct thermal_zone_device *tz = s->private; - struct thermal_debugfs *thermal_dbg = tz->debugfs; + struct thermal_debugfs *thermal_dbg = s->private;
mutex_unlock(&thermal_dbg->lock); }
static int tze_seq_show(struct seq_file *s, void *v) { - struct thermal_zone_device *tz = s->private; + struct thermal_debugfs *thermal_dbg = s->private; + struct thermal_zone_device *tz = thermal_dbg->tz_dbg.tz; struct thermal_trip *trip; struct tz_episode *tze; const char *type; @@ -810,6 +810,8 @@ void thermal_debug_tz_add(struct thermal_zone_device *tz)
tz_dbg = &thermal_dbg->tz_dbg;
+ tz_dbg->tz = tz; + tz_dbg->trips_crossed = kzalloc(sizeof(int) * tz->num_trips, GFP_KERNEL); if (!tz_dbg->trips_crossed) { thermal_debugfs_remove_id(thermal_dbg); @@ -818,20 +820,30 @@ void thermal_debug_tz_add(struct thermal_zone_device *tz)
INIT_LIST_HEAD(&tz_dbg->tz_episodes);
- debugfs_create_file("mitigations", 0400, thermal_dbg->d_top, tz, &tze_fops); + debugfs_create_file("mitigations", 0400, thermal_dbg->d_top, + thermal_dbg, &tze_fops);
tz->debugfs = thermal_dbg; }
void thermal_debug_tz_remove(struct thermal_zone_device *tz) { - struct thermal_debugfs *thermal_dbg = tz->debugfs; + struct thermal_debugfs *thermal_dbg; struct tz_episode *tze, *tmp; struct tz_debugfs *tz_dbg; int *trips_crossed;
- if (!thermal_dbg) + mutex_lock(&tz->lock); + + thermal_dbg = tz->debugfs; + if (!thermal_dbg) { + mutex_unlock(&tz->lock); return; + } + + tz->debugfs = NULL; + + mutex_unlock(&tz->lock);
tz_dbg = &thermal_dbg->tz_dbg;
@@ -844,8 +856,6 @@ void thermal_debug_tz_remove(struct thermal_zone_device *tz) kfree(tze); }
- tz->debugfs = NULL; - mutex_unlock(&thermal_dbg->lock);
thermal_debugfs_remove_id(thermal_dbg);