[scudo] Avoid accessing inaccessible pages in unmap() in secondary

[ChiaHungDuan]

No description provided.

[llvmbot]

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: None (ChiaHungDuan)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/102367.diff

1 Files Affected:

• (modified) compiler-rt/lib/scudo/standalone/secondary.h (+5-1)

diff --git a/compiler-rt/lib/scudo/standalone/secondary.h b/compiler-rt/lib/scudo/standalone/secondary.h
index a9a7c2c8ea8618..27d11dce646dc3 100644
--- a/compiler-rt/lib/scudo/standalone/secondary.h
+++ b/compiler-rt/lib/scudo/standalone/secondary.h
@@ -823,7 +823,11 @@ void MapAllocator<Config>::deallocate(const Options &Options, void *Ptr)
     Cache.store(Options, H->CommitBase, H->CommitSize,
                 reinterpret_cast<uptr>(H + 1), H->MemMap);
   } else {
-    unmap(H->MemMap);
+    // Note that the `H->MapMap` is stored on the pages managed by itself. Take
+    // over the ownership before unmap() so that any operation along with
+    // unmap() won't touch inaccessible pages.
+    MemMapT MemMap = H->MemMap;
+    unmap(MemMap);
   }
 }
 

[ChiaHungDuan]

@Caslyn , could you help verify if this fixes the problem on Fuchsia?

[cferris1000]

Comment nit.

[cferris1000]

MemMap

[ChiaHungDuan]

Done

[Caslyn]

Confirming this clears up issues in Fuchsia - thanks for this fix!