Only initialize the global stack protector once.
Before, dynamic executables would initialize the global stack protector
twice, once for the linker, and once for the executable. This worked
because the result was the same for both initializations, because it
used getauxval(AT_RANDOM), which won't be the case once arc4random gets
used for it.
Bug: http://b/29622562
Change-Id: I7718b1ba8ee8fac7127ab2360cb1088e510fef5c
Test: ran the stack protector tests on angler (32/64bit, static/dynamic)
diff --git a/libc/bionic/__libc_init_main_thread.cpp b/libc/bionic/__libc_init_main_thread.cpp
index 01bb9bb..2643eee 100644
--- a/libc/bionic/__libc_init_main_thread.cpp
+++ b/libc/bionic/__libc_init_main_thread.cpp
@@ -28,14 +28,24 @@
#include "libc_init_common.h"
+#include "private/KernelArgumentBlock.h"
#include "private/bionic_auxv.h"
#include "private/bionic_globals.h"
-#include "private/KernelArgumentBlock.h"
+#include "private/bionic_ssp.h"
#include "pthread_internal.h"
extern "C" int __set_tls(void* ptr);
extern "C" int __set_tid_address(int* tid_address);
+// Declared in "private/bionic_ssp.h".
+uintptr_t __stack_chk_guard = 0;
+
+void __libc_init_global_stack_chk_guard(KernelArgumentBlock& args) {
+ // AT_RANDOM is a pointer to 16 bytes of randomness on the stack.
+ // Take the first 4/8 for the -fstack-protector implementation.
+ __stack_chk_guard = *reinterpret_cast<uintptr_t*>(args.getauxval(AT_RANDOM));
+}
+
// Setup for the main thread. For dynamic executables, this is called by the
// linker _before_ libc is mapped in memory. This means that all writes to
// globals from this function will apply to linker-private copies and will not
@@ -78,7 +88,8 @@
// TODO: the main thread's sched_policy and sched_priority need to be queried.
// The TLS stack guard is set from the global, so ensure that we've initialized the global
- // before we initialize the TLS.
+ // 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_init_global_stack_chk_guard(args);
__init_thread(&main_thread);
diff --git a/libc/bionic/libc_init_common.cpp b/libc/bionic/libc_init_common.cpp
index 2070c9c..919080b 100644
--- a/libc/bionic/libc_init_common.cpp
+++ b/libc/bionic/libc_init_common.cpp
@@ -45,7 +45,6 @@
#include "private/WriteProtected.h"
#include "private/bionic_auxv.h"
#include "private/bionic_globals.h"
-#include "private/bionic_ssp.h"
#include "private/bionic_tls.h"
#include "private/libc_logging.h"
#include "private/thread_private.h"
@@ -62,15 +61,6 @@
// Declared in <unistd.h>.
char** environ;
-// Declared in "private/bionic_ssp.h".
-uintptr_t __stack_chk_guard = 0;
-
-void __libc_init_global_stack_chk_guard(KernelArgumentBlock& args) {
- // AT_RANDOM is a pointer to 16 bytes of randomness on the stack.
- // Take the first 4/8 for the -fstack-protector implementation.
- __stack_chk_guard = *reinterpret_cast<uintptr_t*>(args.getauxval(AT_RANDOM));
-}
-
#if defined(__i386__)
__LIBC_HIDDEN__ void* __libc_sysinfo = nullptr;
@@ -91,7 +81,6 @@
// Initialize libc globals that are needed in both the linker and in libc.
// In dynamic binaries, this is run at least twice for different copies of the
// globals, once for the linker's copy and once for the one in libc.so.
- __libc_init_global_stack_chk_guard(args);
__libc_auxv = args.auxv;
__libc_globals.initialize();
__libc_globals.mutate([&args](libc_globals* globals) {
diff --git a/libc/bionic/libc_init_dynamic.cpp b/libc/bionic/libc_init_dynamic.cpp
index ab48fb8..43bca30 100644
--- a/libc/bionic/libc_init_dynamic.cpp
+++ b/libc/bionic/libc_init_dynamic.cpp
@@ -52,6 +52,7 @@
#include "libc_init_common.h"
#include "private/bionic_globals.h"
+#include "private/bionic_ssp.h"
#include "private/bionic_tls.h"
#include "private/KernelArgumentBlock.h"
@@ -74,6 +75,10 @@
// __libc_init_common() will change the TLS area so the old one won't be accessible anyway.
*args_slot = NULL;
+ // The linker has initialized its copy of the global stack_chk_guard, and filled in the main
+ // thread's TLS slot with that value. Initialize the local global stack guard with its value.
+ __stack_chk_guard = reinterpret_cast<uintptr_t>(tls[TLS_SLOT_STACK_GUARD]);
+
__libc_init_globals(*args);
__libc_init_common(*args);
diff --git a/libc/bionic/libc_init_static.cpp b/libc/bionic/libc_init_static.cpp
index d1494d7..5e06d39 100644
--- a/libc/bionic/libc_init_static.cpp
+++ b/libc/bionic/libc_init_static.cpp
@@ -39,6 +39,7 @@
#include "libc_init_common.h"
#include "pthread_internal.h"
+#include "private/bionic_globals.h"
#include "private/bionic_page.h"
#include "private/bionic_tls.h"
#include "private/KernelArgumentBlock.h"
@@ -85,6 +86,7 @@
__libc_init_main_thread(args);
// Initializing the globals requires TLS to be available for errno.
+ __init_thread_stack_guard(__get_thread());
__libc_init_globals(args);
__libc_init_AT_SECURE(args);
diff --git a/libc/bionic/pthread_create.cpp b/libc/bionic/pthread_create.cpp
index 08d9bed..1956a8f 100644
--- a/libc/bionic/pthread_create.cpp
+++ b/libc/bionic/pthread_create.cpp
@@ -56,6 +56,10 @@
// Slot 0 must point to itself. The x86 Linux kernel reads the TLS from %fs:0.
thread->tls[TLS_SLOT_SELF] = thread->tls;
thread->tls[TLS_SLOT_THREAD_ID] = thread;
+ __init_thread_stack_guard(thread);
+}
+
+void __init_thread_stack_guard(pthread_internal_t* thread) {
// GCC looks in the TLS for the stack guard on x86, so copy it there from our global.
thread->tls[TLS_SLOT_STACK_GUARD] = reinterpret_cast<void*>(__stack_chk_guard);
}
diff --git a/libc/bionic/pthread_internal.h b/libc/bionic/pthread_internal.h
index 0bfbbf1..d2abea0 100644
--- a/libc/bionic/pthread_internal.h
+++ b/libc/bionic/pthread_internal.h
@@ -114,6 +114,7 @@
__LIBC_HIDDEN__ int __init_thread(pthread_internal_t* thread);
__LIBC_HIDDEN__ void __init_tls(pthread_internal_t* thread);
+__LIBC_HIDDEN__ void __init_thread_stack_guard(pthread_internal_t* thread);
__LIBC_HIDDEN__ void __init_alternate_signal_stack(pthread_internal_t*);
__LIBC_HIDDEN__ pthread_t __pthread_internal_add(pthread_internal_t* thread);
diff --git a/libc/private/bionic_globals.h b/libc/private/bionic_globals.h
index b45c0c3..94dd7e8 100644
--- a/libc/private/bionic_globals.h
+++ b/libc/private/bionic_globals.h
@@ -44,7 +44,6 @@
__LIBC_HIDDEN__ extern WriteProtected<libc_globals> __libc_globals;
class KernelArgumentBlock;
-__LIBC_HIDDEN__ void __libc_init_global_stack_chk_guard(KernelArgumentBlock& args);
__LIBC_HIDDEN__ void __libc_init_malloc(libc_globals* globals);
__LIBC_HIDDEN__ void __libc_init_setjmp_cookie(libc_globals* globals, KernelArgumentBlock& args);
__LIBC_HIDDEN__ void __libc_init_vdso(libc_globals* globals, KernelArgumentBlock& args);
