SafeStack: Use correct unsafe stack sizes

Summary:
When deallocating thread stacks, we use one thread's unsafe stack size
to deallocate another thread's unsafe stack; however, the two sizes may
differ. Record an unsafe stack's size in the thread stack linked list.

Reviewers: pcc, eugenis

Reviewed By: eugenis

Subscribers: delcypher, llvm-commits, #sanitizers, kcc

Differential Revision: https://reviews.llvm.org/D51016

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@340308 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 3 insertions, 1 deletions

diff --git a/lib/safestack/safestack.cc b/lib/safestack/safestack.cc
index 920b89b5e..673f5fd30 100644
--- a/lib/safestack/safestack.cc
+++ b/lib/safestack/safestack.cc
@@ -152,6 +152,7 @@ static void *thread_start(void *arg) {
 struct thread_stack_ll {
   struct thread_stack_ll *next;
   void *stack_base;
+  size_t size;
   pid_t pid;
   tid_t tid;
 };
@@ -183,7 +184,7 @@ static void thread_cleanup_handler(void *_iter) {
   while (*stackp) {
     thread_stack_ll *stack = *stackp;
     if (stack->pid != pid || TgKill(stack->pid, stack->tid, 0) == -ESRCH) {
-      UnmapOrDie(stack->stack_base, unsafe_stack_size + unsafe_stack_guard);
+      UnmapOrDie(stack->stack_base, stack->size);
       *stackp = stack->next;
       free(stack);
     } else
@@ -193,6 +194,7 @@ static void thread_cleanup_handler(void *_iter) {
   thread_stack_ll *cur_stack =
       (thread_stack_ll *)malloc(sizeof(thread_stack_ll));
   cur_stack->stack_base = (char *)unsafe_stack_start - unsafe_stack_guard;
+  cur_stack->size = unsafe_stack_size + unsafe_stack_guard;
   cur_stack->pid = pid;
   cur_stack->tid = tid;