empathicqubit/lsnes
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Fix race condition in do_mix_tsc()

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The lock needs to protect count from concurrent update. Especially since
if double increment happens in the wrong place, the routine starts
scribbling memory until whole thing crashes.
This commit is contained in:
Ilari Liusvaara 2015-03-04 21:48:14 +02:00
parent fd65e1e435
commit aade7a9fb8
1 changed files with 2 additions and 2 deletions
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4
src/core/random.cpp
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@ -42,8 +42,8 @@ namespace
static unsigned count = 0;
static uint64_t last_reseed = 0;
static uint64_t buf[slots + 1];
buf[count++] = crandom::arch_get_tsc();
threads::alock h(seed_mutex);
buf[count++] = crandom::arch_get_tsc();
if(count == 0) count = 1; //Shouldn't happen.
if(count == slots || buf[count - 1] - last_reseed > 300000000) {
last_reseed = buf[count - 1];
@ -55,7 +55,6 @@ namespace
std::string get_random_hexstring_64(size_t index)
{
threads::alock h(seed_mutex);
uint64_t buf[7];
uint8_t out[32];
timeval tv;
@ -67,6 +66,7 @@ namespace
buf[0] = tv.tv_sec;
buf[1] = tv.tv_usec;
buf[2] = crandom::arch_get_tsc();
threads::alock h(seed_mutex);
prng.write(buf, sizeof(buf));
prng.read(out, sizeof(out));
return hex::b_to(out, sizeof(out));