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ubsan: Reintroduce signed overflow sanitizer

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In order to mitigate unexpected signed wrap-around[1], bring back the
signed integer overflow sanitizer. It was removed in commit 6aaa31aeb9
("ubsan: remove overflow checks") because it was effectively a no-op
when combined with -fno-strict-overflow (which correctly changes signed
overflow from being "undefined" to being explicitly "wrap around").

Compilers are adjusting their sanitizers to trap wrap-around and to
detecting common code patterns that should not be instrumented
(e.g. "var + offset < var"). Prepare for this and explicitly rename
the option from "OVERFLOW" to "WRAP" to more accurately describe the
behavior.

To annotate intentional wrap-around arithmetic, the helpers
wrapping_add/sub/mul_wrap() can be used for individual statements. At
the function level, the __signed_wrap attribute can be used to mark an
entire function as expecting its signed arithmetic to wrap around. For a
single object file the Makefile can use "UBSAN_SIGNED_WRAP_target.o := n"
to mark it as wrapping, and for an entire directory, "UBSAN_SIGNED_WRAP :=
n" can be used.

Additionally keep these disabled under CONFIG_COMPILE_TEST for now.

Link: https://github.com/KSPP/linux/issues/26 [1]
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Hao Luo <haoluo@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook
2024-01-18 15:06:05 -08:00
parent 918327e9b7
commit 557f8c582a
7 changed files with 137 additions and 2 deletions
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4
lib/ubsan.h
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@@ -124,6 +124,10 @@ 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);