diff options
| -rw-r--r-- | util/nvmutil/nvmutil.c | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/util/nvmutil/nvmutil.c b/util/nvmutil/nvmutil.c index 10c5a6ab..1095a02a 100644 --- a/util/nvmutil/nvmutil.c +++ b/util/nvmutil/nvmutil.c @@ -1172,6 +1172,7 @@ entropy_jitter(void) { struct timeval a, b; unsigned long mix = 0; + long mix_diff; int i; for (i = 0; i < 8; i++) { @@ -1179,7 +1180,15 @@ entropy_jitter(void) getpid(); gettimeofday(&b, NULL); - mix ^= (unsigned long)(b.tv_usec - a.tv_usec); + /* + * prevent negative numbers to prevent overflow, + * which would bias rand to large numbers + */ + mix_diff = (long)(b.tv_usec - a.tv_usec); + if (mix_diff < 0) + mix_diff = -mix_diff; + + mix ^= (unsigned long)(mix_diff); mix ^= (unsigned long)&mix; } |