On Mon, Jun 8, 2020 at 7:51 AM Will Deacon will@kernel.org wrote:
Hey Nick,
On Tue, Jun 02, 2020 at 11:46:31AM -0700, Nick Desaulniers wrote:
On Mon, Jun 1, 2020 at 5:03 PM Kaneda, Erik erik.kaneda@intel.com wrote:
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.
I'll take a look at this tomorrow
The non-kernel runtime of UBSAN would print: runtime error: member access within null pointer of type for this macro.
actypes.h is owned by ACPICA so we typically do not allow compiler-specific extensions because the code is intended to be compiled using the C99 standard without compiler extensions. We could allow this sort of thing in a Linux-specific header file like include/acpi/platform/aclinux.h but I'll take a look at the error as well..
If I'm not allowed to touch that header, it looks like I can include <linux/stddef.h> (rather than my host's <stddef.h>) to get a definition of `offsetof` thats implemented in terms of `__builtin_offsetof`. I should be able to use that to replace uses of ACPI_OFFSET. Are any of these off limits?
It's not so much about not being allowed to touch the header, but rather that the kernel imports the code from a different project:
$ grep -rn ACPI_OFFSET arch/arm64/include/asm/acpi.h:34:#define ACPI_MADT_GICC_MIN_LENGTH ACPI_OFFSET( \ arch/arm64/include/asm/acpi.h:41:#define ACPI_MADT_GICC_SPE (ACPI_OFFSET(struct acpi_madt_generic_interrupt, \
I'm happy to take patches to the stuff under arch/arm64/, fwiw.
Not really sure how to untangle this. Those two cases under arch/arm64/ are straightforward to fix: ``` 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 */ ```
But for one of the warnings you reported, as an example: UBSAN: null-ptr-deref in drivers/acpi/acpica/tbfadt.c:459:37
``` $ ag ACPI_FADT_V2_SIZE include/acpi/actbl.h 394:#define ACPI_FADT_V2_SIZE (u32) (ACPI_FADT_OFFSET (minor_revision) + 1)
drivers/acpi/acpica/tbfadt.c 459: if (acpi_gbl_FADT.header.length <= ACPI_FADT_V2_SIZE) {
$ ag ACPI_FADT_OFFSET ... include/acpi/actbl.h 376:#define ACPI_FADT_OFFSET(f) (u16) ACPI_OFFSET (struct acpi_table_fadt, f) ... ``` So the use of ACPI_FADT_V2_SIZE in drivers/acpi/acpica/tbfadt.c is triggering one of the warnings. ACPI_FADT_V2_SIZE is defined in terms of ACPI_FADT_OFFSET which is defined in terms of ACPI_OFFSET in include/acpi/actbl.h. From the link you posted, include/acpi/actbl.h is from the project under source/include/.
Further, drivers/acpi/acpica/tbfadt.c seems to also be from the upstream project under source/components/tables/tbfadt.c.
Regardless, the second of the two warnings is definitely fixed by my above diff, so let me rephrase the previous commit message with that diff and resend.