From 55b54a999bcdb0b1c1f42b6e1ae670beb0717086 Mon Sep 17 00:00:00 2001 From: Josh Stone Date: Wed, 31 Jan 2018 11:41:29 -0800 Subject: Use a range to identify SIGSEGV in stack guards MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Previously, the `guard::init()` and `guard::current()` functions were returning a `usize` address representing the top of the stack guard, respectively for the main thread and for spawned threads. The `SIGSEGV` handler on `unix` targets checked if a fault was within one page below that address, if so reporting it as a stack overflow. Now `unix` targets report a `Range` representing the guard memory, so it can cover arbitrary guard sizes. Non-`unix` targets which always return `None` for guards now do so with `Option`, so they don't pay any overhead. For `linux-gnu` in particular, the previous guard upper-bound was `stackaddr + guardsize`, as the protected memory was *inside* the stack. This was a glibc bug, and starting from 2.27 they are moving the guard *past* the end of the stack. However, there's no simple way for us to know where the guard page actually lies, so now we declare it as the whole range of `stackaddr ± guardsize`, and any fault therein will be called a stack overflow. This fixes #47863. --- src/libstd/sys/unix/stack_overflow.rs | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) (limited to 'src/libstd/sys/unix/stack_overflow.rs') diff --git a/src/libstd/sys/unix/stack_overflow.rs b/src/libstd/sys/unix/stack_overflow.rs index 51adbc24ae0..40453f9b8a1 100644 --- a/src/libstd/sys/unix/stack_overflow.rs +++ b/src/libstd/sys/unix/stack_overflow.rs @@ -57,9 +57,6 @@ mod imp { use sys_common::thread_info; - // This is initialized in init() and only read from after - static mut PAGE_SIZE: usize = 0; - #[cfg(any(target_os = "linux", target_os = "android"))] unsafe fn siginfo_si_addr(info: *mut libc::siginfo_t) -> usize { #[repr(C)] @@ -102,12 +99,12 @@ mod imp { _data: *mut libc::c_void) { use sys_common::util::report_overflow; - let guard = thread_info::stack_guard().unwrap_or(0); + let guard = thread_info::stack_guard().unwrap_or(0..0); let addr = siginfo_si_addr(info); // If the faulting address is within the guard page, then we print a // message saying so and abort. - if guard != 0 && guard - PAGE_SIZE <= addr && addr < guard { + if guard.start <= addr && addr < guard.end { report_overflow(); rtabort!("stack overflow"); } else { @@ -123,8 +120,6 @@ mod imp { static mut MAIN_ALTSTACK: *mut libc::c_void = ptr::null_mut(); pub unsafe fn init() { - PAGE_SIZE = ::sys::os::page_size(); - let mut action: sigaction = mem::zeroed(); action.sa_flags = SA_SIGINFO | SA_ONSTACK; action.sa_sigaction = signal_handler as sighandler_t; -- cgit 1.4.1-3-g733a5