From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Renlord <me@renlord.com>
Date: Thu, 12 Sep 2019 14:51:51 +1000
Subject: [PATCH] add guard page(s) between static_tls and stack
Signed-off-by: anupritaisno1 <www.anuprita804@gmail.com>
---
libc/bionic/pthread_create.cpp | 29 +++++++++++++++++++----------
1 file changed, 19 insertions(+), 10 deletions(-)
diff --git a/libc/bionic/pthread_create.cpp b/libc/bionic/pthread_create.cpp
index 121b26f82..31c553e25 100644
--- a/libc/bionic/pthread_create.cpp
+++ b/libc/bionic/pthread_create.cpp
@@ -201,9 +201,10 @@ int __init_thread(pthread_internal_t* thread) {
ThreadMapping __allocate_thread_mapping(size_t stack_size, size_t stack_guard_size) {
const StaticTlsLayout& layout = __libc_shared_globals()->static_tls_layout;
- // Allocate in order: stack guard, stack, static TLS, guard page.
+ // Allocate in order: stack guard, stack, guard page, static TLS, guard page.
size_t mmap_size;
if (__builtin_add_overflow(stack_size, stack_guard_size, &mmap_size)) return {};
+ if (__builtin_add_overflow(mmap_size, PTHREAD_GUARD_SIZE, &mmap_size)) return {};
if (__builtin_add_overflow(mmap_size, layout.size(), &mmap_size)) return {};
if (__builtin_add_overflow(mmap_size, PTHREAD_GUARD_SIZE, &mmap_size)) return {};
@@ -212,8 +213,8 @@ ThreadMapping __allocate_thread_mapping(size_t stack_size, size_t stack_guard_si
mmap_size = __BIONIC_ALIGN(mmap_size, PAGE_SIZE);
if (mmap_size < unaligned_size) return {};
- // Create a new private anonymous map. Make the entire mapping PROT_NONE, then carve out a
- // read+write area in the middle.
+ // Create a new private anonymous map. Make the entire mapping PROT_NONE, then carve out
+ // read+write areas for the stack and static TLS
const int flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE;
char* const space = static_cast<char*>(mmap(nullptr, mmap_size, PROT_NONE, flags, -1, 0));
if (space == MAP_FAILED) {
@@ -223,13 +224,21 @@ ThreadMapping __allocate_thread_mapping(size_t stack_size, size_t stack_guard_si
mmap_size, strerror(errno));
return {};
}
- const size_t writable_size = mmap_size - stack_guard_size - PTHREAD_GUARD_SIZE;
- if (mprotect(space + stack_guard_size,
- writable_size,
- PROT_READ | PROT_WRITE) != 0) {
+
+ if (mprotect(space + stack_guard_size, stack_size, PROT_READ | PROT_WRITE) != 0) {
async_safe_format_log(ANDROID_LOG_WARN, "libc",
"pthread_create failed: couldn't mprotect R+W %zu-byte thread mapping region: %s",
- writable_size, strerror(errno));
+ stack_size, strerror(errno));
+ munmap(space, mmap_size);
+ return {};
+ }
+
+ char* const static_tls_space = space + stack_guard_size + stack_size + PTHREAD_GUARD_SIZE;
+
+ if (mprotect(static_tls_space, layout.size(), PROT_READ | PROT_WRITE) != 0) {
+ async_safe_format_log(ANDROID_LOG_WARN, "libc",
+ "pthread_create failed: couldn't mprotect R+W %zu-byte static TLS mapping region: %s",
+ layout.size(), strerror(errno));
munmap(space, mmap_size);
return {};
}
@@ -239,9 +248,9 @@ ThreadMapping __allocate_thread_mapping(size_t stack_size, size_t stack_guard_si
result.mmap_size = mmap_size;
result.mmap_base_unguarded = space + stack_guard_size;
result.mmap_size_unguarded = mmap_size - stack_guard_size - PTHREAD_GUARD_SIZE;
- result.static_tls = space + mmap_size - PTHREAD_GUARD_SIZE - layout.size();
+ result.static_tls = static_tls_space;
result.stack_base = space;
- result.stack_top = result.static_tls;
+ result.stack_top = space + stack_guard_size + stack_size;
return result;
}