Fix TSAN signal interceptor out-of-bound access

[scw]

Summary

signal(2) and sigaction(2) have defined behaviors for invalid signal number
(EINVAL) and some programs rely on it.

The added test case also reveals that MSAN is too strict in this regard.

Test case passed on x86_64 Linux and AArch64 Linux.

[vitalybuka]

Can you please add some basic test, ideally under compiler-rt/test/sanitizer_common/TestCases/Posix/ so we "ninja check-sanitizer" tests asan and msan as well

[scw]

Added test case, needed to update MSAN for it as well. Tested on x86_86 Linux and AArch64 Linux.

[scw]

Oops, that was the old file. This is the actual update.

[vitalybuka]

compiler-rt/lib/msan/msan_interceptors.cpp

1377 ↗

(On Diff #360895)

If so, why not on compiler-rt/lib/sanitizer_common/sanitizer_signal_interceptors.inc:54 before GetHandleSignalMode check?

compiler-rt/test/sanitizer_common/TestCases/Posix/signal.cpp

219 ↗

(On Diff #360895)

Thanks if it works or all platforms.
I expected something basic which just triggers both branches of "if (signo <= 0 || signo >= kMaxSignals)"

[scw]

compiler-rt/lib/msan/msan_interceptors.cpp

1377 ↗

(On Diff #360895)

sanitizer_signal_interceptors.inc is also included by asan_interceptors.cpp which does not intercept signals and does not define kMaxSignals.

compiler-rt/test/sanitizer_common/TestCases/Posix/signal.cpp

219 ↗

(On Diff #360895)

Actually missed a change on relaxing checking the results of SIGCHLD. I'll try this and simplify it if build bots for different platforms complain.

[scw]

Relaxed SIGCHLD handling.

[vitalybuka]

Thank you.
LGTM

compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp

 #include "sanitizer_common/sanitizer_signal_interceptors.inc"
 
 int sigaction_impl(int sig, const __sanitizer_sigaction *act,
                    __sanitizer_sigaction *old) {
   // Note: if we call REAL(sigaction) directly for any reason without proxying
   // the signal handler through rtl_sigaction, very bad things will happen.
   // The handler will run synchronously and corrupt tsan per-thread state.
   SCOPED_INTERCEPTOR_RAW(sigaction, sig, act, old);
+  if (sig <= 0 || sig >= kSigCount) {
+    errno = errno_EINVAL;
+    return -1;
+  }
   __sanitizer_sigaction *sigactions = interceptor_ctx()->sigactions;
   __sanitizer_sigaction old_stored;
   if (old) internal_memcpy(&old_stored, &sigactions[sig], sizeof(old_stored));
   __sanitizer_sigaction newact;
   if (act) {
     // Copy act into sigactions[sig].
     // Can't use struct copy, because compiler can emit call to memcpy.
     // Can't use internal_memcpy, because it copies byte-by-byte,