Merge pull request ClickHouse#100281 from ClickHouse/workaround-asan-fiber-false-positive

alexey-milovidov · web-flow · commit 569e7e9c9049 · 2026-03-21T18:25:01.000+01:00
Unpoison fiber stack before each resume to fix ASan false positives
diff --git a/src/Common/AsyncTaskExecutor.cpp b/src/Common/AsyncTaskExecutor.cpp
@@ -42,6 +42,9 @@ void AsyncTaskExecutor::resume()
 
 void AsyncTaskExecutor::resumeUnlocked()
 {
+    /// Clear stale use-after-scope poisoning on the fiber stack before switching to it.
+    /// See FiberStack::beforeResume() for details.
+    fiber_stack.beforeResume();
     fiber.resume();
 }
 
diff --git a/src/Common/FiberStack.cpp b/src/Common/FiberStack.cpp
@@ -43,7 +43,7 @@ FiberStack::FiberStack(size_t stack_size_)
 {
 }
 
-boost::context::stack_context FiberStack::allocate() const
+boost::context::stack_context FiberStack::allocate()
 {
     size_t num_pages = 1 + (stack_size - 1) / page_size;
 
@@ -72,6 +72,10 @@ boost::context::stack_context FiberStack::allocate() const
         }
     }
 
+    /// Remember the allocation for ASan unpoisoning in beforeResume().
+    stack_base = data;
+    stack_allocation_size = num_bytes;
+
     boost::context::stack_context sctx;
     sctx.size = num_bytes;
     sctx.sp = static_cast< char * >(data) + sctx.size;
diff --git a/src/Common/FiberStack.h b/src/Common/FiberStack.h
@@ -1,5 +1,11 @@
 #pragma once
 #include <boost/context/stack_context.hpp>
+#include <base/sanitizer_defs.h>
+#include <cstddef>
+
+#if __has_include(<sanitizer/asan_interface.h>) && defined(ADDRESS_SANITIZER)
+#   include <sanitizer/asan_interface.h>
+#endif
 
 /// This is an implementation of allocator for fiber stack.
 /// The reference implementation is protected_fixedsize_stack from boost::context.
@@ -16,10 +22,31 @@ class FiberStack
 
     explicit FiberStack(size_t stack_size_ = default_stack_size);
 
-    boost::context::stack_context allocate() const;
+    boost::context::stack_context allocate();
     void deallocate(boost::context::stack_context & sctx) const;
 
+    /// Unpoison the fiber stack memory for ASan.
+    ///
+    /// ASan's use-after-scope detection poisons stack memory when local variables
+    /// go out of scope. On fiber stacks, this poisoning persists across context
+    /// switches (yield/resume), causing false positives when the same stack addresses
+    /// are reused by new frames in subsequent fiber resumes.
+    ///
+    /// This must be called before each fiber resume to clear stale scope poisoning.
+    /// See https://github.com/google/sanitizers/issues/189
+    void beforeResume() const
+    {
+#if defined(ADDRESS_SANITIZER)
+        if (stack_base)
+            ASAN_UNPOISON_MEMORY_REGION(stack_base, stack_allocation_size);
+#endif
+    }
+
 private:
     const size_t stack_size;
     const size_t page_size;
+
+    /// Tracked allocation for ASan unpoisoning.
+    void * stack_base = nullptr;
+    size_t stack_allocation_size = 0;
 };

Original file line number	Diff line number	Diff line change
`@@ -42,6 +42,9 @@ void AsyncTaskExecutor::resume()`
`42`	`42`
`43`	`43`	`void AsyncTaskExecutor::resumeUnlocked()`
`44`	`44`	`{`
	`45`	`+ /// Clear stale use-after-scope poisoning on the fiber stack before switching to it.`
	`46`	`+ /// See FiberStack::beforeResume() for details.`
	`47`	`+ fiber_stack.beforeResume();`
`45`	`48`	`fiber.resume();`
`46`	`49`	`}`
`47`	`50`
Original file line number	Diff line number	Diff line change
`@@ -43,7 +43,7 @@ FiberStack::FiberStack(size_t stack_size_)`
`43`	`43`	`{`
`44`	`44`	`}`
`45`	`45`
`46`		`-boost::context::stack_context FiberStack::allocate() const`
	`46`	`+boost::context::stack_context FiberStack::allocate()`
`47`	`47`	`{`
`48`	`48`	`size_t num_pages = 1 + (stack_size - 1) / page_size;`
`49`	`49`
`@@ -72,6 +72,10 @@ boost::context::stack_context FiberStack::allocate() const`
`72`	`72`	`}`
`73`	`73`	`}`
`74`	`74`
	`75`	`+ /// Remember the allocation for ASan unpoisoning in beforeResume().`
	`76`	`+ stack_base = data;`
	`77`	`+ stack_allocation_size = num_bytes;`
	`78`	`+`
`75`	`79`	`boost::context::stack_context sctx;`
`76`	`80`	`sctx.size = num_bytes;`
`77`	`81`	`sctx.sp = static_cast< char * >(data) + sctx.size;`