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Date:   Mon,  8 Jun 2020 13:38:17 -0700
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Subject: [PATCH v2] arm64: acpi: fix UBSAN warning
From:   Nick Desaulniers <ndesaulniers@google.com>
To:     Will Deacon <will@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>
Cc:     Nick Desaulniers <ndesaulniers@google.com>, stable@vger.kernel.org,
        Ard Biesheuvel <ardb@kernel.org>,
        Enrico Weigelt <info@metux.net>,
        Allison Randal <allison@lohutok.net>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Jeremy Linton <jeremy.linton@arm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
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Will reported a UBSAN warning:

UBSAN: null-ptr-deref in arch/arm64/kernel/smp.c:596:6
member access within null pointer of type 'struct acpi_madt_generic_interrupt'
CPU: 0 PID: 0 Comm: swapper Not tainted 5.7.0-rc6-00124-g96bc42ff0a82 #1
Call trace:
 dump_backtrace+0x0/0x384
 show_stack+0x28/0x38
 dump_stack+0xec/0x174
 handle_null_ptr_deref+0x134/0x174
 __ubsan_handle_type_mismatch_v1+0x84/0xa4
 acpi_parse_gic_cpu_interface+0x60/0xe8
 acpi_parse_entries_array+0x288/0x498
 acpi_table_parse_entries_array+0x178/0x1b4
 acpi_table_parse_madt+0xa4/0x110
 acpi_parse_and_init_cpus+0x38/0x100
 smp_init_cpus+0x74/0x258
 setup_arch+0x350/0x3ec
 start_kernel+0x98/0x6f4

This is from the use of the ACPI_OFFSET in
arch/arm64/include/asm/acpi.h. Replace its use with offsetof from
include/linux/stddef.h which should implement the same logic using
__builtin_offsetof, so that UBSAN wont warn.

Link: https://lore.kernel.org/lkml/20200521100952.GA5360@willie-the-truck/
Cc: stable@vger.kernel.org
Reported-by: Will Deacon <will@kernel.org>
Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
Changes V1 -> V2:
* Just fix one of the two warnings, specific to arm64.
* Put warning in commit message.

 arch/arm64/include/asm/acpi.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
index b263e239cb59..a45366c3909b 100644
--- a/arch/arm64/include/asm/acpi.h
+++ b/arch/arm64/include/asm/acpi.h
@@ -12,6 +12,7 @@
 #include <linux/efi.h>
 #include <linux/memblock.h>
 #include <linux/psci.h>
+#include <linux/stddef.h>
 
 #include <asm/cputype.h>
 #include <asm/io.h>
@@ -31,14 +32,14 @@
  * is therefore used to delimit the MADT GICC structure minimum length
  * appropriately.
  */
-#define ACPI_MADT_GICC_MIN_LENGTH   ACPI_OFFSET(  \
+#define ACPI_MADT_GICC_MIN_LENGTH   offsetof(  \
 	struct acpi_madt_generic_interrupt, efficiency_class)
 
 #define BAD_MADT_GICC_ENTRY(entry, end)					\
 	(!(entry) || (entry)->header.length < ACPI_MADT_GICC_MIN_LENGTH || \
 	(unsigned long)(entry) + (entry)->header.length > (end))
 
-#define ACPI_MADT_GICC_SPE  (ACPI_OFFSET(struct acpi_madt_generic_interrupt, \
+#define ACPI_MADT_GICC_SPE  (offsetof(struct acpi_madt_generic_interrupt, \
 	spe_interrupt) + sizeof(u16))
 
 /* Basic configuration for ACPI */
-- 
2.27.0.278.ge193c7cf3a9-goog