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From:   Qian Cai <cai@lca.pw>
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Subject: Clang and UBSAN: member access within null pointer of type
Message-Id: <CA6078C3-3489-40E4-B756-A0AF6DB3A3A5@lca.pw>
Date:   Thu, 7 May 2020 09:42:50 -0400
Cc:     clang-built-linux@googlegroups.com,
        LKML <linux-kernel@vger.kernel.org>
To:     Nick Desaulniers <ndesaulniers@google.com>,
        Nathan Chancellor <natechancellor@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Running a Clang (9.0.1) build kernel with UBSAN generated a few warnings =
during boot,

[    0.000000] UBSAN: null-ptr-deref in =
drivers/acpi/acpica/tbfadt.c:459:37
[    0.000000] member access within null pointer of type 'struct =
acpi_table_fadt'
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted =
5.7.0-rc4-next-20200507 #2
[    0.000000] Call trace:
[    0.000000]  dump_backtrace+0x0/0x22c
[    0.000000]  show_stack+0x28/0x34
[    0.000000]  dump_stack+0x104/0x194
[    0.000000]  handle_null_ptr_deref+0xdc/0x10c
[    0.000000]  __ubsan_handle_type_mismatch_v1+0x64/0x78
[    0.000000]  acpi_tb_create_local_fadt+0x104/0x6ec
[    0.000000]  acpi_tb_parse_fadt+0xa0/0x1a0
[    0.000000]  acpi_tb_parse_root_table+0x284/0x2ac
[    0.000000]  acpi_initialize_tables+0xb4/0xd0
[    0.000000]  acpi_table_init+0x68/0x88
[    0.000000]  acpi_boot_table_init+0x108/0x1a0
[    0.000000]  setup_arch+0xec/0x1f4
[    0.000000]  start_kernel+0x94/0x56c

[    0.000000] UBSAN: null-ptr-deref in arch/arm64/kernel/smp.c:596:6
[    0.000000] member access within null pointer of type 'struct =
acpi_madt_generic_interrupt'
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted =
5.7.0-rc4-next-20200507 #2
[    0.000000] Call trace:
[    0.000000]  dump_backtrace+0x0/0x22c
[    0.000000]  show_stack+0x28/0x34
[    0.000000]  dump_stack+0x104/0x194
[    0.000000]  handle_null_ptr_deref+0xdc/0x10c
[    0.000000]  __ubsan_handle_type_mismatch_v1+0x64/0x78
[    0.000000]  acpi_parse_gic_cpu_interface+0x40/0xa8
[    0.000000]  acpi_parse_entries_array+0x1d4/0x2e8
[    0.000000]  acpi_table_parse_entries_array+0x11c/0x138
[    0.000000]  acpi_table_parse_madt+0x84/0xb0
[    0.000000]  acpi_parse_and_init_cpus+0x24/0x80
[    0.000000]  smp_init_cpus+0x38/0x17c
[    0.000000]  setup_arch+0x140/0x1f4
[    0.000000]  start_kernel+0x94/0x56c

[  255.388250] UBSAN: null-ptr-deref in ./fs/xfs/xfs_sysfs.h:37:23
[  255.394898] member access within null pointer of type 'struct =
xfs_kobj'
[  255.402346] CPU: 230 PID: 2364 Comm: modprobe Tainted: G             =
L    5.7.0-rc4-next-20200507 #2
[  255.412191] Hardware name: HPE Apollo 70             /C01_APACHE_MB   =
      , BIOS L50_5.13_1.11 06/18/2019
[  255.422641] Call trace:
[  255.425811]  dump_backtrace+0x0/0x22c
[  255.430188]  show_stack+0x28/0x34
[  255.434225]  dump_stack+0x104/0x194
[  255.438441]  handle_null_ptr_deref+0xdc/0x10c
[  255.443511]  __ubsan_handle_type_mismatch_v1+0x64/0x78
[  255.450016]  init_module+0x130/0x1d4 [xfs]
[  255.454831]  do_one_initcall+0x6c/0x144
[  255.459383]  do_init_module+0x100/0x388
[  255.463931]  load_module+0x2518/0x2b9c
[  255.468404]  __se_sys_finit_module+0x144/0x150
[  255.473560]  __arm64_sys_finit_module+0x54/0x88
[  255.478804]  do_el0_svc+0x128/0x1dc
[  255.483010]  el0_sync_handler+0xd0/0x268
[  255.487655]  el0_sync+0x164/0x180
[  255.491782] =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D
[  255.769799] =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D
[  255.779164] UBSAN: null-ptr-deref in ./fs/xfs/xfs_sysfs.h:37:23
[  255.785816] member access within null pointer of type 'struct =
xfs_kobj'
[  255.793268] CPU: 132 PID: 2363 Comm: mount Tainted: G             L   =
 5.7.0-rc4-next-20200507 #2
[  255.802854] Hardware name: HPE Apollo 70             /C01_APACHE_MB   =
      , BIOS L50_5.13_1.11 06/18/2019
[  255.813306] Call trace:
[  255.816471]  dump_backtrace+0x0/0x22c
[  255.820849]  show_stack+0x28/0x34
[  255.824882]  dump_stack+0x104/0x194
[  255.829090]  handle_null_ptr_deref+0xdc/0x10c
[  255.834163]  __ubsan_handle_type_mismatch_v1+0x64/0x78
[  255.840665]  xfs_mountfs+0x310/0xc64 [xfs]
[  255.846071]  xfs_fc_fill_super+0x5cc/0x75c [xfs]
[  255.851411]  get_tree_bdev+0x24c/0x328
[  255.856463]  xfs_fc_get_tree+0x24/0x30 [xfs]
[  255.861453]  vfs_get_tree+0x54/0x158
[  255.865754]  do_mount+0x80c/0xaf0
[  255.869786]  __arm64_sys_mount+0xe0/0x18c
[  255.874510]  do_el0_svc+0x128/0x1dc
[  255.878720]  el0_sync_handler+0xd0/0x268
[  255.883357]  el0_sync+0x164/0x180=