From 8fc203ba5face785681b3f06eac1d116d937499b Mon Sep 17 00:00:00 2001 From: nobu Date: Tue, 3 Jul 2018 05:12:52 +0000 Subject: [PATCH] cont.c: handle errors for getcontext() It may raise an error in a certain security configuration. It is very likely to trigger a segmentation fault if `getcontext()` failed silently and we just let it keep going. Related to https://bugs.ruby-lang.org/issues/14883 [Fix GH-1903] Based on the patch from Lion Yang From: Lion Yang git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63835 b2dd03c8-39d4-4d8f-98ff-823fe69b080e --- cont.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/cont.c b/cont.c index 634733807a..d1356efaa8 100644 --- a/cont.c +++ b/cont.c @@ -142,14 +142,21 @@ enum fiber_status { #define FIBER_RUNNABLE_P(fib) (FIBER_CREATED_P(fib) || FIBER_SUSPENDED_P(fib)) #if FIBER_USE_NATIVE && !defined(_WIN32) -static inline void +static inline int fiber_context_create(ucontext_t *context, void (*func)(), void *arg, void *ptr, size_t size) { - getcontext(context); + if (getcontext(context) < 0) return -1; + /* + * getcontext() may fail by some reasons: + * 1. SELinux policy banned one of "rt_sigprocmask", + * "sigprocmask" or "swapcontext"; + * 2. libseccomp (aka. syscall filter) banned one of them. + */ context->uc_link = NULL; context->uc_stack.ss_sp = ptr; context->uc_stack.ss_size = size; makecontext(context, func, 0); + return 0; } #endif @@ -856,7 +863,9 @@ fiber_initialize_machine_stack_context(rb_fiber_t *fib, size_t size) ptr = fiber_machine_stack_alloc(size); fib->ss_sp = ptr; fib->ss_size = size; - fiber_context_create(&fib->context, fiber_entry, NULL, fib->ss_sp, fib->ss_size); + if (fiber_context_create(&fib->context, fiber_entry, NULL, fib->ss_sp, fib->ss_size)) { + rb_raise(rb_eFiberError, "can't get context for creating fiber: %s", ERRNOMSG); + } sec->machine.stack_start = (VALUE*)(ptr + STACK_DIR_UPPER(0, size)); sec->machine.stack_maxsize = size - RB_PAGE_SIZE; #endif