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https://github.com/libffi/libffi/commit/01db744b4af8665f9b7494d00cc2a1cc45ee9636
From 01db744b4af8665f9b7494d00cc2a1cc45ee9636 Mon Sep 17 00:00:00 2001
From: KJ Tsanaktsidis <kj@kjtsanaktsidis.id.au>
Date: Fri, 20 Sep 2024 20:00:49 +1000
Subject: [PATCH] Disable ASAN in ffi_call_int functions (#858)
The pattern for several of the architectures is for ffi_call_int to
stack-allocate some arguments + the registers, and then
ffi_call_$ARCH will pop the top of that structure into registers, and
then adjust the stack pointer such that the alloca'd buffer _becomes_
the stack-passed arguments for the function being called.
If libffi is compiled with ASAN, then there will be a redzone inserted
after the alloca'd buffer which is marked as poisoned. This redzone
appears beyond the end of $sp upon entry to the called function.
If the called function does anything to use this stack memory, ASAN will
notice that it's poisoned and report an error.
This commit fixes the situation (on the architectures that I have access
to) disabling instrumentation for ffi_call_int; that means there will be
no alloca redzone left on the shadow-stack.
--- a/include/ffi_common.h
+++ b/include/ffi_common.h
@@ -83,6 +83,23 @@ char *alloca ();
#include <stdio.h>
#endif
+#ifndef __SANITIZE_ADDRESS__
+# ifdef __clang__
+# if __has_feature(address_sanitizer)
+# define FFI_ASAN
+# endif
+# endif
+#endif
+#ifdef __SANITIZE_ADDRESS__
+#define FFI_ASAN
+#endif
+
+#ifdef FFI_ASAN
+#define FFI_ASAN_NO_SANITIZE __attribute__((no_sanitize_address))
+#else
+#define FFI_ASAN_NO_SANITIZE
+#endif
+
#ifdef FFI_DEBUG
NORETURN void ffi_assert(const char *expr, const char *file, int line);
void ffi_stop_here(void);
--- a/src/aarch64/ffi.c
+++ b/src/aarch64/ffi.c
@@ -645,7 +645,10 @@ extern void ffi_call_SYSV (struct call_context *context, void *frame,
void *closure) FFI_HIDDEN;
/* Call a function with the provided arguments and capture the return
- value. */
+ value.
+ n.b. ffi_call_SYSV will steal the alloca'd `stack` variable here for use
+ _as its own stack_ - so we need to compile this function without ASAN */
+FFI_ASAN_NO_SANITIZE
static void
ffi_call_int (ffi_cif *cif, void (*fn)(void), void *orig_rvalue,
void **avalue, void *closure)
--- a/src/x86/ffi.c
+++ b/src/x86/ffi.c
@@ -270,6 +270,9 @@ extern void FFI_DECLARE_FASTCALL ffi_call_i386(struct call_frame *, char *) FFI_
#if defined(_MSC_VER)
#pragma runtime_checks("s", off)
#endif
+/* n.b. ffi_call_unix64 will steal the alloca'd `stack` variable here for use
+ _as its own stack_ - so we need to compile this function without ASAN */
+FFI_ASAN_NO_SANITIZE
static void
ffi_call_int (ffi_cif *cif, void (*fn)(void), void *rvalue,
void **avalue, void *closure)
--- a/src/x86/ffi64.c
+++ b/src/x86/ffi64.c
@@ -557,6 +557,9 @@ ffi_prep_cif_machdep (ffi_cif *cif)
return FFI_OK;
}
+/* n.b. ffi_call_unix64 will steal the alloca'd `stack` variable here for use
+ _as its own stack_ - so we need to compile this function without ASAN */
+FFI_ASAN_NO_SANITIZE
static void
ffi_call_int (ffi_cif *cif, void (*fn)(void), void *rvalue,
void **avalue, void *closure)
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