Fixes for fuzzing on NetBSD with concurrent fuzzer-threads

Do not support fuzzing forkees and vforkees. Doing so is non-trivial
in the current design of the fuzzer, as there is need to call wait(2)
function dedicated for every forkee and vforkee in a thread. In the
context of fuzzing in multiple instances of multiple processes this
means that there is need a redesign of the threading/process model
and wait(2)ing every tracee with a dedicated thread or iteration step
in a loop (perhaps try kqueue(2)/kevent(2)?).

A wait(2)-like function called for WAIT_ANY caused gathering reports
from other fuzzer-threads and in the result abnormal hangs.

While there, do not discard SIGTRAP that is emitted by user, and pass
this signal to the tracee.

2 files changed, 9 insertions, 5 deletions

diff --git a/netbsd/arch.c b/netbsd/arch.c
index f65d005d..81d41b0f 100644
--- a/netbsd/arch.c
+++ b/netbsd/arch.c
@@ -202,7 +202,7 @@ static bool arch_checkWait(run_t* run) {
     /* All queued wait events must be tested when SIGCHLD was delivered */
     for (;;) {
         int status;
-        pid_t pid = TEMP_FAILURE_RETRY(waitpid(WAIT_ANY, &status, WALLSIG | WNOHANG));
+        pid_t pid = TEMP_FAILURE_RETRY(waitpid(ptracePid, &status, WALLSIG | WNOHANG));
         if (pid == 0) {
             return false;
         }
diff --git a/netbsd/trace.c b/netbsd/trace.c
index 3ba47709..3fba2122 100644
--- a/netbsd/trace.c
+++ b/netbsd/trace.c
@@ -855,10 +855,12 @@ static void arch_traceEvent(run_t* run HF_ATTR_UNUSED, pid_t pid) {
         if (ptrace(PT_GET_PROCESS_STATE, pid, &state, sizeof(state)) != -1) {
             switch (state.pe_report_event) {
             case PTRACE_FORK:
-                LOG_D("PID: %d child trap (TRAP_CHLD) : fork (PTRACE_FORK)", pid);
-                break;
             case PTRACE_VFORK:
-                LOG_D("PID: %d child trap (TRAP_CHLD) : vfork (PTRACE_VFORK)", pid);
+                LOG_D("PID: %d child trap (TRAP_CHLD) : fork (%s)", pid, state.pe_report_event == PTRACE_FORK ? "PTRACE_FORK" : "PTRACE_VFORK");
+                /* Do not support fuzzing (v)forkees */
+                int status;
+                waitpid(state.pe_other_pid, &status, 0);
+                ptrace(PT_DETACH, state.pe_other_pid, (void *)1, 0);
                 break;
             case PTRACE_VFORK_DONE:
                 LOG_D("PID: %d child trap (TRAP_CHLD) : vfork (PTRACE_VFORK_DONE)", pid);
@@ -888,7 +890,9 @@ static void arch_traceEvent(run_t* run HF_ATTR_UNUSED, pid_t pid) {
         LOG_E("PID: %d unexpected syscall exit trap (TRAP_SCX)", pid);
         break;
     default:
-        LOG_D("PID: %d unknown trap si_code=%d", pid, info.psi_siginfo.si_code);
+        /* Other trap, pass it over to tracee */
+        sig = SIGTRAP;
+        LOG_D("PID: %d other trap si_code=%d", pid, info.psi_siginfo.si_code);
         break;
     }