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[ovs-dev,04/11] stopwatch: Fix buffer underflow when computing percentiles.

Message ID 20211217131721.30994.23948.stgit@dceara.remote.csb
State Superseded
Headers show
Series Fix UndefinedBehaviorSanitizer reported issues and enable it in CI. | expand

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Commit Message

Dumitru Ceara Dec. 17, 2021, 1:17 p.m. UTC 
UB Sanitizer report:
  lib/stopwatch.c:119:22: runtime error: index 18446744073709551615 out of bounds for type 'long long unsigned int [50]'
      #0 0x698358 in calc_percentile lib/stopwatch.c:119
      #1 0x69ada1 in add_sample lib/stopwatch.c:231
      #2 0x69c086 in stopwatch_end_sample_protected lib/stopwatch.c:386
      #3 0x69c522 in stopwatch_thread lib/stopwatch.c:441
      #4 0x684bae in ovsthread_wrapper lib/ovs-thread.c:383
      #5 0x7f042838b298 in start_thread (/lib64/libpthread.so.0+0x9298)
      #6 0x7f04277f2352 in clone (/lib64/libc.so.6+0x100352)

Signed-off-by: Dumitru Ceara <dceara@redhat.com>
---
 lib/stopwatch.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)
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Patch

diff --git a/lib/stopwatch.c b/lib/stopwatch.c
index f5602163bc16..1c71df1a127e 100644
--- a/lib/stopwatch.c
+++ b/lib/stopwatch.c
@@ -114,7 +114,6 @@  static void
 calc_percentile(unsigned long long n_samples, struct percentile *pctl,
                 unsigned long long new_sample)
 {
-
     if (n_samples < P_SQUARE_MIN) {
         pctl->samples[n_samples - 1] = new_sample;
     }
@@ -228,13 +227,12 @@  add_sample(struct stopwatch *sw, unsigned long long new_sample)
         sw->min = new_sample;
     }
 
-    calc_percentile(sw->n_samples, &sw->pctl, new_sample);
-
     if (sw->n_samples++ == 0) {
         sw->short_term.average = sw->long_term.average = new_sample;
         return;
     }
 
+    calc_percentile(sw->n_samples, &sw->pctl, new_sample);
     calc_average(&sw->short_term, new_sample);
     calc_average(&sw->long_term, new_sample);
 }