linux-kernel - [PATCH] ubsan: Entirely disable alignment checks under UBSAN

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Message-ID: <202005291236.000FCB6@keescook>
Date:   Fri, 29 May 2020 12:37:35 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Randy Dunlap <rdunlap@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Elena Petrova <lenaptr@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] ubsan: Entirely disable alignment checks under UBSAN_TRAP

Commit 8d58f222e85f ("ubsan: disable UBSAN_ALIGNMENT under
COMPILE_TEST") tried to fix the pathological results of UBSAN_ALIGNMENT
with UBSAN_TRAP (which objtool would rightly scream about), but it made
an assumption about how COMPILE_TEST gets set (it is not set for
randconfig). As a result, we need a bigger hammer here: just don't allow
the alignment checks with the trap mode.

Reported-by: Randy Dunlap <rdunlap@...radead.org>
Link: https://lore.kernel.org/lkml/742521db-1e8c-0d7a-1ed4-a908894fb497@infradead.org/
Fixes: 8d58f222e85f ("ubsan: disable UBSAN_ALIGNMENT under COMPILE_TEST")
Signed-off-by: Kees Cook <keescook@...omium.org>
Acked-by: Randy Dunlap <rdunlap@...radead.org>
---
 lib/Kconfig.ubsan | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
index 929211039bac..27bcc2568c95 100644
--- a/lib/Kconfig.ubsan
+++ b/lib/Kconfig.ubsan
@@ -63,7 +63,7 @@ config UBSAN_SANITIZE_ALL
 config UBSAN_ALIGNMENT
 	bool "Enable checks for pointers alignment"
 	default !HAVE_EFFICIENT_UNALIGNED_ACCESS
-	depends on !X86 || !COMPILE_TEST
+	depends on !UBSAN_TRAP
 	help
 	  This option enables the check of unaligned memory accesses.
 	  Enabling this option on architectures that support unaligned
-- 
2.25.1


-- 
Kees Cook