Hi,
On 6/8/20 3:38 PM, Nick Desaulniers wrote:
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.
I looked at the longer thread about this, given that it appears to be a
false positive with respect to the macro, I tend to prefer Ard's
suggestion of just changing the offset value (1 should be sufficient
rather than 0) to avoid this kind of problem in the future.
But either way, this change looks fine too.
Reviewed-by: Jeremy Linton <jeremy.linton@xxxxxxx>
Thanks,
Link: https://lore.kernel.org/lkml/20200521100952.GA5360@willie-the-truck/
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Will Deacon <will@xxxxxxxxxx>
Suggested-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
---
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 */
