[compiler-rt] Do not initialize the allocator on free(nullptr). (PR #74366)

[Evgenii Stepanov via llvm-commits]

https://github.com/eugenis created https://github.com/llvm/llvm-project/pull/74366

Bionic calls free(nullptr) before the allocator settings are finalized. Scudo should not run allocator initialization at that time. Doing so causes various bad things to happen, like mapping primary regions with the wrong PROT_MTE setting.

>From 4250f5b12a904d79df771ae7c34a22be1f74a8ba Mon Sep 17 00:00:00 2001
From: Evgenii Stepanov <eugenis at google.com>
Date: Mon, 4 Dec 2023 11:29:29 -0800
Subject: [PATCH] Do not initialize the allocator on free(nullptr).

Bionic calls free(nullptr) before the allocator settings are finalized.
Scudo should not run allocator initialization at that time. Doing so
causes various bad things to happen, like mapping primary regions with
the wrong PROT_MTE setting.
---
 compiler-rt/lib/scudo/standalone/combined.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/compiler-rt/lib/scudo/standalone/combined.h b/compiler-rt/lib/scudo/standalone/combined.h
index 25c597199a658..79c3a36c742b4 100644
--- a/compiler-rt/lib/scudo/standalone/combined.h
+++ b/compiler-rt/lib/scudo/standalone/combined.h
@@ -522,6 +522,9 @@ class Allocator {
 
   NOINLINE void deallocate(void *Ptr, Chunk::Origin Origin, uptr DeleteSize = 0,
                            UNUSED uptr Alignment = MinAlignment) {
+    if (UNLIKELY(!Ptr))
+      return;
+
     // For a deallocation, we only ensure minimal initialization, meaning thread
     // local data will be left uninitialized for now (when using ELF TLS). The
     // fallback cache will be used instead. This is a workaround for a situation
@@ -530,9 +533,6 @@ class Allocator {
     // being destroyed properly. Any other heap operation will do a full init.
     initThreadMaybe(/*MinimalInit=*/true);
 
-    if (UNLIKELY(!Ptr))
-      return;
-
 #ifdef GWP_ASAN_HOOKS
     if (UNLIKELY(GuardedAlloc.pointerIsMine(Ptr))) {
       GuardedAlloc.deallocate(Ptr);