From 02ac6f41e5569ec28d625bb005155903f64cc9ee Mon Sep 17 00:00:00 2001 From: "Gregory P. Smith" Date: Thu, 4 Mar 2021 21:49:30 -0800 Subject: bpo-43390: Set SA_ONSTACK in PyOS_setsig (GH-24730) This is friendlier to other in-process code that an extension module or embedding use could pull in such as CGo where tiny stacks are the norm and sigaltstack() has been used to provide for signal handlers. Without this, signals received by a process using tiny stacks may lead to stack overflow crashes. --- .../next/Core and Builtins/2021-03-03-17-58-49.bpo-43390.epPpwV.rst | 6 ++++++ Python/pylifecycle.c | 5 ++++- 2 files changed, 10 insertions(+), 1 deletion(-) create mode 100644 Misc/NEWS.d/next/Core and Builtins/2021-03-03-17-58-49.bpo-43390.epPpwV.rst diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-03-03-17-58-49.bpo-43390.epPpwV.rst b/Misc/NEWS.d/next/Core and Builtins/2021-03-03-17-58-49.bpo-43390.epPpwV.rst new file mode 100644 index 0000000..ae115db --- /dev/null +++ b/Misc/NEWS.d/next/Core and Builtins/2021-03-03-17-58-49.bpo-43390.epPpwV.rst @@ -0,0 +1,6 @@ +CPython now sets the ``SA_ONSTACK`` flag in ``PyOS_setsig`` for the VM's +default signal handlers. This is friendlier to other in-process code that +an extension module or embedding use could pull in (such as Golang's cgo) +where tiny thread stacks are the norm and ``sigaltstack()`` has been used to +provide for signal handlers. This is a no-op change for the vast majority +of processes that don't use sigaltstack. diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c index ec77084..d03c6c0 100644 --- a/Python/pylifecycle.c +++ b/Python/pylifecycle.c @@ -2884,7 +2884,10 @@ PyOS_setsig(int sig, PyOS_sighandler_t handler) struct sigaction context, ocontext; context.sa_handler = handler; sigemptyset(&context.sa_mask); - context.sa_flags = 0; + /* Using SA_ONSTACK is friendlier to other C/C++/Golang-VM code that + * extension module or embedding code may use where tiny thread stacks + * are used. https://bugs.python.org/issue43390 */ + context.sa_flags = SA_ONSTACK; if (sigaction(sig, &context, &ocontext) == -1) return SIG_ERR; return ocontext.sa_handler; -- cgit v0.12