From 3a778ff50f7091b8a64875c8ed95bfaacf3d334c Mon Sep 17 00:00:00 2001 From: Cherry Zhang Date: Fri, 22 Jan 2021 09:47:59 -0500 Subject: runtime: check for g0 stack last in signal handler In the signal handler, we adjust gsingal's stack to the stack where the signal is delivered. TSAN may deliver signals to the g0 stack, so we have a special case for the g0 stack. However, we don't have very good accuracy in determining the g0 stack's bounds, as it is system allocated and we don't know where it is exactly. If g0.stack.lo is too low, the condition may be triggered incorrectly, where we thought the signal is delivered to the g0 stack but it is actually not. In this case, as the stack bounds is actually wrong, when the stack grows, it may go below the (inaccurate) lower bound, causing "morestack on gsignal" crash. Check for g0 stack last to avoid this situation. There could still be false positives, but for those cases we'll crash either way. (If we could in some way determine the g0 stack bounds accurately, this would not matter (but probably doesn't hurt).) Fixes #43853. Change-Id: I759717c5aa2b0deb83ffb23e57b7625a6b249ee8 Reviewed-on: https://go-review.googlesource.com/c/go/+/285772 Trust: Cherry Zhang Reviewed-by: Michael Pratt --- src/runtime/proc.go | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'src/runtime/proc.go') diff --git a/src/runtime/proc.go b/src/runtime/proc.go index aa44c625c5..d51dcb0d22 100644 --- a/src/runtime/proc.go +++ b/src/runtime/proc.go @@ -1251,6 +1251,11 @@ func mstart() { // Initialize stack bounds from system stack. // Cgo may have left stack size in stack.hi. // minit may update the stack bounds. + // + // Note: these bounds may not be very accurate. + // We set hi to &size, but there are things above + // it. The 1024 is supposed to compensate this, + // but is somewhat arbitrary. size := _g_.stack.hi if size == 0 { size = 8192 * sys.StackGuardMultiplier -- cgit v1.3-5-g9baa