On Thu, May 21, 2020 at 11:09:53AM +0100, Will Deacon wrote: > Hi folks, > > I just tried booting the arm64 for-kernelci branch under QEMU (version > 4.2.50 (v4.2.0-779-g4354edb6dcc7)) with UBSAN enabled, and I see a > couple of NULL pointer dereferences reported at boot. I think they're > both GIC related (log below). I don't see a panic with UBSAN disabled, > so something's fishy here.
May I ask you the QEMU command line please - just to make sure I can replicate it. > Please can you take a look when you get a chance? I haven't had time to see > if this is a regression or not, but I don't think it's particularly serious > as I have all sorts of horrible stuff enabled in my .config, since I'm > trying to chase down another bug: > > https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/plain/arch/arm64/configs/fuzzing.config?h=fuzzing/arm64-kernelci-20200519&id=c149cf6a51aa4f72d53fc681c6661094e93ef660 > > (on top of defconfig) > > CONFIG_FAIL_PAGE_ALLOC may be to blame. Not sure about that, they are both quite cryptic, I wonder if UBSAN is not tricked by the ACPI_OFFSET macro - need to debug it further to understand what's going on here. Thanks, Lorenzo > Cheers, > > Will > > --->8 > > [ 0.000000][ T0] > ================================================================================ > [ 0.000000][ T0] UBSAN: null-ptr-deref in > drivers/acpi/acpica/tbfadt.c:459:37 > [ 0.000000][ T0] member access within null pointer of type 'struct > acpi_table_fadt' > [ 0.000000][ T0] CPU: 0 PID: 0 Comm: swapper Not tainted > 5.7.0-rc6-00124-g96bc42ff0a82 #1 > [ 0.000000][ T0] Call trace: > [ 0.000000][ T0] dump_backtrace+0x0/0x384 > [ 0.000000][ T0] show_stack+0x28/0x38 > [ 0.000000][ T0] dump_stack+0xec/0x174 > [ 0.000000][ T0] handle_null_ptr_deref+0x134/0x174 > [ 0.000000][ T0] __ubsan_handle_type_mismatch_v1+0x84/0xa4 > [ 0.000000][ T0] acpi_tb_create_local_fadt+0x1d4/0x1418 > [ 0.000000][ T0] acpi_tb_parse_fadt+0x108/0x4b8 > [ 0.000000][ T0] acpi_tb_parse_root_table+0x380/0x578 > [ 0.000000][ T0] acpi_initialize_tables+0x140/0x194 > [ 0.000000][ T0] acpi_table_init+0x90/0xcc > [ 0.000000][ T0] acpi_boot_table_init+0xfc/0x1c8 > [ 0.000000][ T0] setup_arch+0x2b4/0x3ec > [ 0.000000][ T0] start_kernel+0x98/0x6f4 > [ 0.000000][ T0] > ================================================================================ > > [ 0.000000][ T0] > ================================================================================ > [ 0.000000][ T0] UBSAN: null-ptr-deref in arch/arm64/kernel/smp.c:596:6 > [ 0.000000][ T0] member access within null pointer of type 'struct > acpi_madt_generic_interrupt' > [ 0.000000][ T0] CPU: 0 PID: 0 Comm: swapper Not tainted > 5.7.0-rc6-00124-g96bc42ff0a82 #1 > [ 0.000000][ T0] Call trace: > [ 0.000000][ T0] dump_backtrace+0x0/0x384 > [ 0.000000][ T0] show_stack+0x28/0x38 > [ 0.000000][ T0] dump_stack+0xec/0x174 > [ 0.000000][ T0] handle_null_ptr_deref+0x134/0x174 > [ 0.000000][ T0] __ubsan_handle_type_mismatch_v1+0x84/0xa4 > [ 0.000000][ T0] acpi_parse_gic_cpu_interface+0x60/0xe8 > [ 0.000000][ T0] acpi_parse_entries_array+0x288/0x498 > [ 0.000000][ T0] acpi_table_parse_entries_array+0x178/0x1b4 > [ 0.000000][ T0] acpi_table_parse_madt+0xa4/0x110 > [ 0.000000][ T0] acpi_parse_and_init_cpus+0x38/0x100 > [ 0.000000][ T0] smp_init_cpus+0x74/0x258 > [ 0.000000][ T0] setup_arch+0x350/0x3ec > [ 0.000000][ T0] start_kernel+0x98/0x6f4 > [ 0.000000][ T0] > ================================================================================
