linux-hardening - [PATCH v2] ubsan: Avoid i386 UBSAN handler crashes with Clang

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Date: Wed, 24 Apr 2024 15:40:29 -0700
From: Kees Cook <keescook@...omium.org>
To: Marco Elver <elver@...gle.com>
Cc: Kees Cook <keescook@...omium.org>,
	Erhard Furtner <erhard_f@...lbox.org>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	llvm@...ts.linux.dev,
	kasan-dev@...glegroups.com,
	linux-hardening@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] ubsan: Avoid i386 UBSAN handler crashes with Clang

When generating Runtime Calls, Clang doesn't respect the -mregparm=3
option used on i386. Hopefully this will be fixed correctly in Clang 19:
https://github.com/llvm/llvm-project/pull/89707
but we need to fix this for earlier Clang versions today. Force the
calling convention to use non-register arguments.

Reported-by: Erhard Furtner <erhard_f@...lbox.org>
Closes: https://github.com/KSPP/linux/issues/350
Signed-off-by: Kees Cook <keescook@...omium.org>
---
Cc: Marco Elver <elver@...gle.com>
Cc: Andrey Konovalov <andreyknvl@...il.com>
Cc: Andrey Ryabinin <ryabinin.a.a@...il.com>
Cc: Nathan Chancellor <nathan@...nel.org>
Cc: Nick Desaulniers <ndesaulniers@...gle.com>
Cc: Bill Wendling <morbo@...gle.com>
Cc: Justin Stitt <justinstitt@...gle.com>
Cc: llvm@...ts.linux.dev
Cc: kasan-dev@...glegroups.com
Cc: linux-hardening@...r.kernel.org
 v2:
   - use email address in Reported-by
   - link to upstream llvm bug in ubsan.h comment
   - drop needless /**/
   - explicitly test Clang version
 v1: https://lore.kernel.org/lkml/20240424162942.work.341-kees@kernel.org/
---
 lib/ubsan.h | 41 +++++++++++++++++++++++++++--------------
 1 file changed, 27 insertions(+), 14 deletions(-)

diff --git a/lib/ubsan.h b/lib/ubsan.h
index 50ef50811b7c..07e37d4429b4 100644
--- a/lib/ubsan.h
+++ b/lib/ubsan.h
@@ -124,19 +124,32 @@ typedef s64 s_max;
 typedef u64 u_max;
 #endif
 
-void __ubsan_handle_add_overflow(void *data, void *lhs, void *rhs);
-void __ubsan_handle_sub_overflow(void *data, void *lhs, void *rhs);
-void __ubsan_handle_mul_overflow(void *data, void *lhs, void *rhs);
-void __ubsan_handle_negate_overflow(void *_data, void *old_val);
-void __ubsan_handle_divrem_overflow(void *_data, void *lhs, void *rhs);
-void __ubsan_handle_type_mismatch(struct type_mismatch_data *data, void *ptr);
-void __ubsan_handle_type_mismatch_v1(void *_data, void *ptr);
-void __ubsan_handle_out_of_bounds(void *_data, void *index);
-void __ubsan_handle_shift_out_of_bounds(void *_data, void *lhs, void *rhs);
-void __ubsan_handle_builtin_unreachable(void *_data);
-void __ubsan_handle_load_invalid_value(void *_data, void *val);
-void __ubsan_handle_alignment_assumption(void *_data, unsigned long ptr,
-					 unsigned long align,
-					 unsigned long offset);
+/*
+ * When generating Runtime Calls, Clang doesn't respect the -mregparm=3
+ * option used on i386: https://github.com/llvm/llvm-project/issues/89670
+ * Fix this for earlier Clang versions by forcing the calling convention
+ * to use non-register arguments.
+ */
+#if defined(CONFIG_X86_32) && \
+    defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 190000
+# define ubsan_linkage asmlinkage
+#else
+# define ubsan_linkage
+#endif
+
+void ubsan_linkage __ubsan_handle_add_overflow(void *data, void *lhs, void *rhs);
+void ubsan_linkage __ubsan_handle_sub_overflow(void *data, void *lhs, void *rhs);
+void ubsan_linkage __ubsan_handle_mul_overflow(void *data, void *lhs, void *rhs);
+void ubsan_linkage __ubsan_handle_negate_overflow(void *_data, void *old_val);
+void ubsan_linkage __ubsan_handle_divrem_overflow(void *_data, void *lhs, void *rhs);
+void ubsan_linkage __ubsan_handle_type_mismatch(struct type_mismatch_data *data, void *ptr);
+void ubsan_linkage __ubsan_handle_type_mismatch_v1(void *_data, void *ptr);
+void ubsan_linkage __ubsan_handle_out_of_bounds(void *_data, void *index);
+void ubsan_linkage __ubsan_handle_shift_out_of_bounds(void *_data, void *lhs, void *rhs);
+void ubsan_linkage __ubsan_handle_builtin_unreachable(void *_data);
+void ubsan_linkage __ubsan_handle_load_invalid_value(void *_data, void *val);
+void ubsan_linkage __ubsan_handle_alignment_assumption(void *_data, unsigned long ptr,
+						       unsigned long align,
+						       unsigned long offset);
 
 #endif
-- 
2.34.1