4.19-stable review patch. If anyone has any objections, please let me know.
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From: Tom Zanussi tom.zanussi@linux.intel.com
commit 9f0bbf3115ca9f91f43b7c74e9ac7d79f47fc6c2 upstream.
Because there may be random garbage beyond a string's null terminator, it's not correct to copy the the complete character array for use as a hist trigger key. This results in multiple histogram entries for the 'same' string key.
So, in the case of a string key, use strncpy instead of memcpy to avoid copying in the extra bytes.
Before, using the gdbus entries in the following hist trigger as an example:
# echo 'hist:key=comm' > /sys/kernel/debug/tracing/events/sched/sched_waking/trigger # cat /sys/kernel/debug/tracing/events/sched/sched_waking/hist
...
{ comm: ImgDecoder #4 } hitcount: 203 { comm: gmain } hitcount: 213 { comm: gmain } hitcount: 216 { comm: StreamTrans #73 } hitcount: 221 { comm: mozStorage #3 } hitcount: 230 { comm: gdbus } hitcount: 233 { comm: StyleThread#5 } hitcount: 253 { comm: gdbus } hitcount: 256 { comm: gdbus } hitcount: 260 { comm: StyleThread#4 } hitcount: 271
...
# cat /sys/kernel/debug/tracing/events/sched/sched_waking/hist | egrep gdbus | wc -l 51
After:
# cat /sys/kernel/debug/tracing/events/sched/sched_waking/hist | egrep gdbus | wc -l 1
Link: http://lkml.kernel.org/r/50c35ae1267d64eee975b8125e151e600071d4dc.1549309756...
Cc: Namhyung Kim namhyung@kernel.org Cc: stable@vger.kernel.org Fixes: 79e577cbce4c4 ("tracing: Support string type key properly") Signed-off-by: Tom Zanussi tom.zanussi@linux.intel.com Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/trace/trace_events_hist.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -4621,9 +4621,10 @@ static inline void add_to_key(char *comp /* ensure NULL-termination */ if (size > key_field->size - 1) size = key_field->size - 1; - }
- memcpy(compound_key + key_field->offset, key, size); + strncpy(compound_key + key_field->offset, (char *)key, size); + } else + memcpy(compound_key + key_field->offset, key, size); }
static void