DivestOS/Patches/LineageOS-21.0/android_bionic/0002-Graphene_Bionic_Hardening-10.patch

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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Daniel Micay <danielmicay@gmail.com>
Date: Wed, 2 Dec 2015 23:37:28 -0500
Subject: [PATCH] switch pthread_atfork handler allocation to mmap
Signed-off-by: anupritaisno1 <www.anuprita804@gmail.com>
---
libc/bionic/pthread_atfork.cpp | 35 ++++++++++++++++++++++++++++------
1 file changed, 29 insertions(+), 6 deletions(-)
diff --git a/libc/bionic/pthread_atfork.cpp b/libc/bionic/pthread_atfork.cpp
index 0dcabdfb2..6306052ee 100644
--- a/libc/bionic/pthread_atfork.cpp
+++ b/libc/bionic/pthread_atfork.cpp
@@ -29,6 +29,9 @@
#include <errno.h>
#include <pthread.h>
#include <stdlib.h>
+#include <sys/mman.h>
+#include <sys/prctl.h>
+#include <unistd.h>
#include "platform/bionic/macros.h"
@@ -43,6 +46,8 @@ struct atfork_t {
void* dso_handle;
};
+static atfork_t* pool;
+
class atfork_list_t {
public:
constexpr atfork_list_t() : first_(nullptr), last_(nullptr) {}
@@ -101,7 +106,8 @@ class atfork_list_t {
last_ = entry->prev;
}
- free(entry);
+ entry->next = pool;
+ pool = entry;
}
atfork_t* first_;
@@ -154,18 +160,35 @@ void __bionic_atfork_run_parent() {
// __register_atfork is the name used by glibc
extern "C" int __register_atfork(void (*prepare)(void), void (*parent)(void),
void(*child)(void), void* dso) {
- atfork_t* entry = reinterpret_cast<atfork_t*>(malloc(sizeof(atfork_t)));
- if (entry == nullptr) {
- return ENOMEM;
+ pthread_mutex_lock(&g_atfork_list_mutex);
+
+ if (!pool) {
+ size_t page_size = getpagesize();
+ char* page = static_cast<char*>(mmap(NULL, page_size, PROT_READ|PROT_WRITE,
+ MAP_ANONYMOUS|MAP_PRIVATE, -1, 0));
+ if (page == MAP_FAILED) {
+ pthread_mutex_unlock(&g_atfork_list_mutex);
+ return ENOMEM;
+ }
+
+ prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, page, page_size,
+ "atfork handlers");
+
+ for (char* it = page; it < page + page_size - sizeof(atfork_t); it += sizeof(atfork_t)) {
+ atfork_t* node = reinterpret_cast<atfork_t*>(it);
+ node->next = pool;
+ pool = node;
+ }
}
+ atfork_t* entry = pool;
+ pool = entry->next;
+
entry->prepare = prepare;
entry->parent = parent;
entry->child = child;
entry->dso_handle = dso;
- pthread_mutex_lock(&g_atfork_list_mutex);
-
g_atfork_list.push_back(entry);
pthread_mutex_unlock(&g_atfork_list_mutex);