From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Daniel Micay <danielmicay@gmail.com>
Date: Sat, 1 Oct 2016 05:11:44 -0400
Subject: [PATCH] make __stack_chk_guard read-only at runtime
Signed-off-by: anupritaisno1 <www.anuprita804@gmail.com>
---
libc/bionic/__libc_init_main_thread.cpp | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/libc/bionic/__libc_init_main_thread.cpp b/libc/bionic/__libc_init_main_thread.cpp
index 95f46e9fa..7e1e7cbcb 100644
--- a/libc/bionic/__libc_init_main_thread.cpp
+++ b/libc/bionic/__libc_init_main_thread.cpp
@@ -28,6 +28,9 @@
#include "libc_init_common.h"
+#include <limits.h>
+#include <sys/mman.h>
+
#include <async_safe/log.h>
#include "private/KernelArgumentBlock.h"
@@ -35,14 +38,14 @@
#include "private/bionic_defs.h"
#include "private/bionic_elf_tls.h"
#include "private/bionic_globals.h"
-#include "private/bionic_ssp.h"
#include "pthread_internal.h"
extern "C" pid_t __getpid();
extern "C" int __set_tid_address(int* tid_address);
// Declared in "private/bionic_ssp.h".
-uintptr_t __stack_chk_guard = 0;
+__attribute__((aligned(PAGE_SIZE)))
+uintptr_t __stack_chk_guard[PAGE_SIZE / sizeof(uintptr_t)] = {0};
static pthread_internal_t main_thread;
@@ -107,10 +110,16 @@ void __init_tcb_dtv(bionic_tcb* tcb) {
// Note in particular that it is not possible to return from any existing
// stack frame with stack protector enabled after this function is called.
extern "C" void android_reset_stack_guards() {
+ if (mprotect(__stack_chk_guard, sizeof(__stack_chk_guard), PROT_READ|PROT_WRITE) == -1) {
+ async_safe_fatal("mprotect __stack_chk_guard: %s", strerror(errno));
+ }
// The TLS stack guard is set from the global, so ensure that we've initialized the global
// before we initialize the TLS. Dynamic executables will initialize their copy of the global
// stack protector from the one in the main thread's TLS.
- __libc_safe_arc4random_buf(&__stack_chk_guard, sizeof(__stack_chk_guard));
+ __libc_safe_arc4random_buf(&__stack_chk_guard[0], sizeof(__stack_chk_guard[0]));
+ if (mprotect(__stack_chk_guard, sizeof(__stack_chk_guard), PROT_READ) == -1) {
+ async_safe_fatal("mprotect __stack_chk_guard: %s", strerror(errno));
+ }
__init_tcb_stack_guard(__get_bionic_tcb());
}