# Re: \[PATCH\] ACPICA: fix UBSAN warning using \_\_builtin\_offsetof - From: Jung-uk Kim \ - Date: 2020-06-10 23:46:26 - List: linux-arm-kernel - Page: https://ratatoskr.run/linux-arm-kernel/2020/06/5996154 - Thread: https://ratatoskr.run/linux-arm-kernel/2020/05/5973580/t.md ```text On 20. 6. 10., Nick Desaulniers wrote: > On Wed, Jun 10, 2020 at 4:07 PM Kaneda, Erik [ref] wrote: >> >> +JKim (for FreeBSD's perspective) >> >>> -----Original Message----- >>> From: Nick Desaulniers >>> Sent: Monday, June 1, 2020 4:18 PM >>> To: Moore, Robert ; Kaneda, Erik >>> [ref]; Wysocki, Rafael J [ref]; >>> Len Brown [ref] >>> Cc: Ard Biesheuvel ; dvyukov@google.com; >>> glider@google.com; guohanjun@huawei.com; linux-arm- >>> kernel@lists.infradead.org; linux-kernel@vger.kernel.org; >>> lorenzo.pieralisi@arm.com; mark.rutland@arm.com; >>> ndesaulniers@google.com; pcc@google.com; rjw@rjwysocki.net; >>> will@kernel.org; stable@vger.kernel.org; linux-acpi@vger.kernel.org; >>> devel@acpica.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 >>> >> Hi, >> >>> Looks like the emulated offsetof macro ACPI_OFFSET is causing these. We >>> can avoid this by using the compiler builtin, __builtin_offsetof. >>> >> This doesn't really fly because __builtin_offsetof is a compiler extension. >> >> It looks like a lot of stddef.h files do this: >> >> #define offsetof(a,b) __builtin_offset(a,b) >> >> So does anyone have objections to ACPI_OFFSET being defined to offsetof()? >> >> This will allow a host OS project project to use their own definitions of offsetof in place of ACPICA's. >> If they don't have a definition for offsetof, we can supply the old one as a fallback. >> >> Here's a patch: >> >> --- a/include/acpi/actypes.h >> +++ b/include/acpi/actypes.h >> @@ -504,11 +504,17 @@ typedef u64 acpi_integer; >> #define ACPI_SUB_PTR(t, a, b) ACPI_CAST_PTR (t, (ACPI_CAST_PTR (u8, (a)) - (acpi_size)(b))) >> #define ACPI_PTR_DIFF(a, b) ((acpi_size) (ACPI_CAST_PTR (u8, (a)) - ACPI_CAST_PTR (u8, (b)))) >> >> +/* Use an existing definiton for offsetof */ > > s/definiton/definition/ > >> + >> +#ifndef offsetof >> +#define offsetof(d,f) ACPI_PTR_DIFF (&(((d *) 0)->f), (void *) 0) >> +#endif > > If this header doesn't explicitly include or > , won't translation units that include > get different definitions of ACPI_OFFSET based on > whether they explicitly or transitively included before > including ? Theoretically, a translation unit in the > kernel could include actypes.h, have no includes of linux/stddef.h, > then get UBSAN errors again from using this definition? > > I don't mind using offsetof in place of the builtin (since it > typically will be implemented in terms of the builtin, or is at least > for the case specific to the Linux kernel). But if it's used, we > should include the header that defines it properly, and we should not > use the host's IMO. Is there a platform specific way to > include the platform's stddef.h here? > > Maybe linux/stddef.h should be included in > include/acpi/platform/aclinux.h, then include/acpi/platform/acenv.h > included in include/acpi/actypes.h, such that ACPI_OFFSET is defined > in terms of offsetof defined from that transitive dependency of > headers? (or do we get a circular inclusion trying to do that?) Actually, I think we should let platform-specific acfoo.h decide what to do here, i.e., #ifndef ACPI_OFFSET #define ACPI_OFFSET(d, f) ... #endif Jung-uk Kim >> + >> /* Pointer/Integer type conversions */ >> >> #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) offsetof (d,f) >> #define ACPI_PHYSADDR_TO_PTR(i) ACPI_TO_POINTER(i) >> #define ACPI_PTR_TO_PHYSADDR(i) ACPI_TO_INTEGER(i) >> >> Thanks, >> Erik >> >>> 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: >>> Reported-by: Will Deacon >>> Suggested-by: Ard Biesheuvel >>> Signed-off-by: Nick Desaulniers >>> --- >>> 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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ```