Hi Andrey,
Enabling CONFIG_KASAN_HW_TAGS and running the resulting kernel on
non-MTE hardware panics with an undefined STG instruction from
mte_set_mem_tag_range():
./scripts/faddr2line vmlinux kasan_unpoison_task_stack+0x18/0x40
kasan_unpoison_task_stack+0x18/0x40:
mte_set_mem_tag_range at arch/arm64/include/asm/mte-kasan.h:71
(inlined by) mte_set_mem_tag_range at arch/arm64/include/asm/mte-kasan.h:56
(inlined by) kasan_unpoison at mm/kasan/kasan.h:363
(inlined by) kasan_unpoison_task_stack at mm/kasan/common.c:72
The full trace:
------------[ cut here ]------------
kernel BUG at arch/arm64/kernel/traps.c:406!
Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Not tainted 5.12.0-rc1-00002-ge76afd1d69f3-dirty #2
pstate: 00000085 (nzcv daIf -PAN -UAO -TCO BTYPE=--)
pc : do_undefinstr+0x2c8/0x2e8
lr : do_undefinstr+0x2d4/0x2e8
sp : ffffc07baeaa3cf0
x29: ffffc07baeaa3cf0 x28: ffffc07baeab3280
x27: ffffc07baeaa9a00 x26: ffffc07baeaa7000
x25: ffffc07baeab3964 x24: ffffc07baeaa9c00
x23: 0000000040000085 x22: ffffc07baed7f0e0
x21: 00000000d9200800 x20: ffffc07baeab3280
x19: ffffc07baeaa3d80 x18: 0000000000000200
x17: 000000000000000b x16: 0000000000007fff
x15: 00000000ffffffff x14: 0000000000000000
x13: 0000000000000048 x12: ffffc07baeab3280
x11: ffff64d0ffc00294 x10: 0000000000000000
x9 : 0000000000000000 x8 : 00000000389fd980
x7 : ffff64d0ffbde5b8 x6 : 0000000000000000
x5 : ffff64d0ffb99880 x4 : ffffc07baeab5710
x3 : ffffc07baed7f0f0 x2 : 0000000000000000
x1 : ffffc07baeab3280 x0 : 0000000040000085
Call trace:
do_undefinstr+0x2c8/0x2e8
el1_undef+0x30/0x50
el1_sync_handler+0x8c/0xc8
el1_sync+0x70/0x100
kasan_unpoison_task_stack+0x18/0x40
sched_init+0x390/0x3f0
start_kernel+0x2cc/0x540
0x0
Code: 17ffff8a f9401bf7 17ffffc8 f9001bf7 (d4210000)
random: get_random_bytes called from print_oops_end_marker+0x2c/0x68 with crng_init=0
---[ end trace c881f708bdfe36c8 ]---
If MTE is not available, I thought we should not end up calling the MTE
backend but it seems that kasan expects the backend to skip the
undefined instructions.
Does kasan fall back to sw_tags if hw_tags are not available or it just
disables kasan altogether?
--
Catalin
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On Fri, Mar 5, 2021 at 6:11 PM Catalin Marinas [off-list ref] wrote:
Hi Andrey,
Hi Catalin,
Enabling CONFIG_KASAN_HW_TAGS and running the resulting kernel on
non-MTE hardware panics with an undefined STG instruction from
mte_set_mem_tag_range():
./scripts/faddr2line vmlinux kasan_unpoison_task_stack+0x18/0x40
kasan_unpoison_task_stack+0x18/0x40:
mte_set_mem_tag_range at arch/arm64/include/asm/mte-kasan.h:71
(inlined by) mte_set_mem_tag_range at arch/arm64/include/asm/mte-kasan.h:56
(inlined by) kasan_unpoison at mm/kasan/kasan.h:363
(inlined by) kasan_unpoison_task_stack at mm/kasan/common.c:72
This is weird. kasan_unpoison_task_stack() is only defined when
CONFIG_KASAN_STACK is enabled, which shouldn't be enablable for
HW_TAGS.
Are you using the mainline kernel?
Could you share the kernel config that you use?
The full trace:
------------[ cut here ]------------
kernel BUG at arch/arm64/kernel/traps.c:406!
Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Not tainted 5.12.0-rc1-00002-ge76afd1d69f3-dirty #2
pstate: 00000085 (nzcv daIf -PAN -UAO -TCO BTYPE=--)
pc : do_undefinstr+0x2c8/0x2e8
lr : do_undefinstr+0x2d4/0x2e8
sp : ffffc07baeaa3cf0
x29: ffffc07baeaa3cf0 x28: ffffc07baeab3280
x27: ffffc07baeaa9a00 x26: ffffc07baeaa7000
x25: ffffc07baeab3964 x24: ffffc07baeaa9c00
x23: 0000000040000085 x22: ffffc07baed7f0e0
x21: 00000000d9200800 x20: ffffc07baeab3280
x19: ffffc07baeaa3d80 x18: 0000000000000200
x17: 000000000000000b x16: 0000000000007fff
x15: 00000000ffffffff x14: 0000000000000000
x13: 0000000000000048 x12: ffffc07baeab3280
x11: ffff64d0ffc00294 x10: 0000000000000000
x9 : 0000000000000000 x8 : 00000000389fd980
x7 : ffff64d0ffbde5b8 x6 : 0000000000000000
x5 : ffff64d0ffb99880 x4 : ffffc07baeab5710
x3 : ffffc07baed7f0f0 x2 : 0000000000000000
x1 : ffffc07baeab3280 x0 : 0000000040000085
Call trace:
do_undefinstr+0x2c8/0x2e8
el1_undef+0x30/0x50
el1_sync_handler+0x8c/0xc8
el1_sync+0x70/0x100
kasan_unpoison_task_stack+0x18/0x40
sched_init+0x390/0x3f0
start_kernel+0x2cc/0x540
0x0
Code: 17ffff8a f9401bf7 17ffffc8 f9001bf7 (d4210000)
random: get_random_bytes called from print_oops_end_marker+0x2c/0x68 with crng_init=0
---[ end trace c881f708bdfe36c8 ]---
If MTE is not available, I thought we should not end up calling the MTE
backend but it seems that kasan expects the backend to skip the
undefined instructions.
Does kasan fall back to sw_tags if hw_tags are not available or it just
disables kasan altogether?
If the hardware doesn't support HW_TAGS, KASAN should get disabled.
If the compiler doesn't support HW_TAGS, I think KASAN will fall back
to GENERIC through oldconfig.
Thanks!
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel