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Search for other free cores when bind fails #68

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Search for other free cores when bind fails #68

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63 changes: 48 additions & 15 deletions afl-fuzz.c
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Original file line number Diff line number Diff line change
Expand Up @@ -488,30 +488,63 @@ static void bind_to_free_cpu(void) {

closedir(d);

for (i = 0; i < cpu_core_count; i++) if (!cpu_used[i]) break;

if (i == cpu_core_count) {
int bound = 0;
int tried_bind = 0;
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rename to bind_attempts

int saved_errno = 0;

SAYF("\n" cLRD "[-] " cRST
"Uh-oh, looks like all %u CPU cores on your system are allocated to\n"
" other instances of afl-fuzz (or similar CPU-locked tasks). Starting\n"
" another fuzzer on this machine is probably a bad plan, but if you are\n"
" absolutely sure, you can set AFL_NO_AFFINITY and try again.\n",
cpu_core_count);
for (i = 0; i < cpu_core_count; i++) {

if (!cpu_used[i]) {
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let's decrease the indentation by inverting the condition:

for (i = 0; i < cpu_core_count; i++) {
  if (cpu_used[i])
    continue;

  <the code trying to bind>
}


OKF("Found a free CPU core, attempting bind to #%u.", i);

CPU_ZERO(&c);
CPU_SET(i, &c);

if (sched_setaffinity(0, sizeof(c), &c)) {
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similar suggestion here:

  if (!sched_setaffinity(0, sizeof(c), &c)) {
    cpu_aff = i;
    bound = 1;
    break;
  }

  saved_errno = errno;
  tried_bind++;
  WARNF("Binding attempt failed; looking for another core...");


FATAL("No more free CPU cores");
saved_errno = errno;
tried_bind++;
WARNF("Binding attempt failed; looking for another core...");

} else {

cpu_aff = i;
bound = 1;
break;

}
}
}

OKF("Found a free CPU core, binding to #%u.", i);
if (!bound) {
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  ...
  if (bound)
    return;

  <error reporting code here>
}


cpu_aff = i;
if (tried_bind == 0) {

CPU_ZERO(&c);
CPU_SET(i, &c);
SAYF("\n" cLRD "[-] " cRST
"Uh-oh, looks like all %u CPU cores on your system are allocated to\n"
" other instances of afl-fuzz (or similar CPU-locked tasks). Starting\n"
" another fuzzer on this machine is probably a bad plan, but if you are\n"
" absolutely sure, you can set AFL_NO_AFFINITY and try again.\n\n",
cpu_core_count);
FATAL("No more free CPU cores");

if (sched_setaffinity(0, sizeof(c), &c))
PFATAL("sched_setaffinity failed");
} else {

SAYF("\n" cLRD "[-] " cRST
"Uh-oh, afl-fuzz found %u apparently free CPU cores, but the system\n"
" wouldn't let us bind to any of them. This can happen if we do not\n"
" have CAP_SYS_NICE, or if we are running in a container that is\n"
" restricted to a certain set of CPUs that already have processes bound\n"
" to them. For a quick workaround, set AFL_NO_AFFINITY and try again.\n",
tried_bind);

errno = saved_errno;
PFATAL("sched_setaffinity failed");

}
}

}

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