linux-kernel - [PATCH] ACPICA: fix UBSAN warning using __builtin

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Message-Id: <20200601231805.207441-1-ndesaulniers@google.com>
Date:   Mon,  1 Jun 2020 16:18:05 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Robert Moore <robert.moore@...el.com>,
        Erik Kaneda <erik.kaneda@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Len Brown <lenb@...nel.org>
Cc:     Ard Biesheuvel <ardb@...nel.org>, dvyukov@...gle.com,
        glider@...gle.com, guohanjun@...wei.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        lorenzo.pieralisi@....com, mark.rutland@....com,
        ndesaulniers@...gle.com, pcc@...gle.com, rjw@...ysocki.net,
        will@...nel.org, stable@...r.kernel.org,
        linux-acpi@...r.kernel.org, devel@...ica.org
Subject: [PATCH] ACPICA: fix UBSAN warning using __builtin_offsetof

Will reported UBSAN warnings:
UBSAN: null-ptr-deref in drivers/acpi/acpica/tbfadt.c:459:37
UBSAN: null-ptr-deref in arch/arm64/kernel/smp.c:596:6

Looks like the emulated offsetof macro ACPI_OFFSET is causing these. We
can avoid this by using the compiler builtin, __builtin_offsetof.

The non-kernel runtime of UBSAN would print:
runtime error: member access within null pointer of type
for this macro.

Link: https://lore.kernel.org/lkml/20200521100952.GA5360@willie-the-truck/
Cc: stable@...r.kernel.org
Reported-by: Will Deacon <will@...nel.org>
Suggested-by: Ard Biesheuvel <ardb@...nel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
---
 include/acpi/actypes.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/acpi/actypes.h b/include/acpi/actypes.h
index 4defed58ea33..04359c70b198 100644
--- a/include/acpi/actypes.h
+++ b/include/acpi/actypes.h
@@ -508,7 +508,7 @@ typedef u64 acpi_integer;
 
 #define ACPI_TO_POINTER(i)              ACPI_CAST_PTR (void, (acpi_size) (i))
 #define ACPI_TO_INTEGER(p)              ACPI_PTR_DIFF (p, (void *) 0)
-#define ACPI_OFFSET(d, f)               ACPI_PTR_DIFF (&(((d *) 0)->f), (void *) 0)
+#define ACPI_OFFSET(d, f)               __builtin_offsetof(d, f)
 #define ACPI_PHYSADDR_TO_PTR(i)         ACPI_TO_POINTER(i)
 #define ACPI_PTR_TO_PHYSADDR(i)         ACPI_TO_INTEGER(i)
 
-- 
2.27.0.rc2.251.g90737beb825-goog