[compiler-rt] [scudo] Do not unmap the memory containing the this object in unmapRingBuffer (PR #83034)

[Fabio D'Urso via llvm-commits]

https://github.com/fabio-d updated https://github.com/llvm/llvm-project/pull/83034

>From da6fa7f7407242bc331de34f941cfafd1cedbe73 Mon Sep 17 00:00:00 2001
From: Fabio D'Urso <fdurso at google.com>
Date: Mon, 26 Feb 2024 18:09:06 +0100
Subject: [PATCH 1/2] [scudo] Do not unmap the memory containing the this
 object in unmapRingBuffer

---
 compiler-rt/lib/scudo/standalone/combined.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/compiler-rt/lib/scudo/standalone/combined.h b/compiler-rt/lib/scudo/standalone/combined.h
index cd5a07be1576e9..197c6d85c9b06c 100644
--- a/compiler-rt/lib/scudo/standalone/combined.h
+++ b/compiler-rt/lib/scudo/standalone/combined.h
@@ -1610,8 +1610,9 @@ class Allocator {
     // is very important.
     RB->RawStackDepotMap.unmap(RB->RawStackDepotMap.getBase(),
                                RB->RawStackDepotMap.getCapacity());
-    RB->RawRingBufferMap.unmap(RB->RawRingBufferMap.getBase(),
-                               RB->RawRingBufferMap.getCapacity());
+    MemMapT RawRingBufferMap = RB->RawRingBufferMap;
+    RawRingBufferMap.unmap(RawRingBufferMap.getBase(),
+                           RawRingBufferMap.getCapacity());
     atomic_store(&RingBufferAddress, 0, memory_order_release);
   }
 

>From 6608d26179202f652e9db110c3e7d1dfe69cdc7d Mon Sep 17 00:00:00 2001
From: Fabio D'Urso <fdurso at google.com>
Date: Mon, 26 Feb 2024 23:07:09 +0100
Subject: [PATCH 2/2] fixup! [scudo] Do not unmap the memory containing the
 this object in unmapRingBuffer

---
 compiler-rt/lib/scudo/standalone/combined.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/compiler-rt/lib/scudo/standalone/combined.h b/compiler-rt/lib/scudo/standalone/combined.h
index 197c6d85c9b06c..581be0deeb9372 100644
--- a/compiler-rt/lib/scudo/standalone/combined.h
+++ b/compiler-rt/lib/scudo/standalone/combined.h
@@ -1610,6 +1610,9 @@ class Allocator {
     // is very important.
     RB->RawStackDepotMap.unmap(RB->RawStackDepotMap.getBase(),
                                RB->RawStackDepotMap.getCapacity());
+    // Note that the `RB->RawRingBufferMap` is stored on the pages managed by
+    // itself. Take over the ownership before calling unmap() so that any operation
+    // along with unmap() won't touch inaccessible pages.
     MemMapT RawRingBufferMap = RB->RawRingBufferMap;
     RawRingBufferMap.unmap(RawRingBufferMap.getBase(),
                            RawRingBufferMap.getCapacity());