Re: [RFC PATCH v1] powerpc: Enable KFENCE for PPC32

Christophe Leroy
2021-03-02T09:49:59Z

Le 02/03/2021 à 10:21, Alexander Potapenko a écrit :
>> [ 14.998426] BUG: KFENCE: invalid read in finish_task_switch.isra.0+0x54/0x23c
>> [ 14.998426]
>> [ 15.007061] Invalid read at 0x(ptrval):
>> [ 15.010906] finish_task_switch.isra.0+0x54/0x23c
>> [ 15.015633] kunit_try_run_case+0x5c/0xd0
>> [ 15.019682] kunit_generic_run_threadfn_adapter+0x24/0x30
>> [ 15.025099] kthread+0x15c/0x174
>> [ 15.028359] ret_from_kernel_thread+0x14/0x1c
>> [ 15.032747]
>> [ 15.034251] CPU: 0 PID: 111 Comm: kunit_try_catch Tainted: G B
>> 5.12.0-rc1-s3k-dev-01534-g4f14ae75edf0-dirty #4674
>> [ 15.045811] ==================================================================
>> [ 15.053324] # test_invalid_access: EXPECTATION FAILED at mm/kfence/kfence_test.c:636
>> [ 15.053324] Expected report_matches(&expect) to be true, but is false
>> [ 15.068359] not ok 21 - test_invalid_access
>
> The test expects the function name to be test_invalid_access, i. e.
> the first line should be "BUG: KFENCE: invalid read in
> test_invalid_access".
> The error reporting function unwinds the stack, skips a couple of
> "uninteresting" frames
> (https://elixir.bootlin.com/linux/v5.12-rc1/source/mm/kfence/report.c#L43)
> and uses the first "interesting" one frame to print the report header
> (https://elixir.bootlin.com/linux/v5.12-rc1/source/mm/kfence/report.c#L226).
>
> It's strange that test_invalid_access is missing altogether from the
> stack trace - is that expected?
> Can you try printing the whole stacktrace without skipping any frames
> to see if that function is there?
>

Booting with 'no_hash_pointers" I get the following. Does it helps ?

[ 16.837198] ==================================================================
[ 16.848521] BUG: KFENCE: invalid read in finish_task_switch.isra.0+0x54/0x23c
[ 16.848521]
[ 16.857158] Invalid read at 0xdf98800a:
[ 16.861004] finish_task_switch.isra.0+0x54/0x23c
[ 16.865731] kunit_try_run_case+0x5c/0xd0
[ 16.869780] kunit_generic_run_threadfn_adapter+0x24/0x30
[ 16.875199] kthread+0x15c/0x174
[ 16.878460] ret_from_kernel_thread+0x14/0x1c
[ 16.882847]
[ 16.884351] CPU: 0 PID: 111 Comm: kunit_try_catch Tainted: G B
5.12.0-rc1-s3k-dev-01534-g4f14ae75edf0-dirty #4674
[ 16.895908] NIP: c016eb8c LR: c02f50dc CTR: c016eb38
[ 16.900963] REGS: e2449d90 TRAP: 0301 Tainted: G B
(5.12.0-rc1-s3k-dev-01534-g4f14ae75edf0-dirty)
[ 16.911386] MSR: 00009032 <EE,ME,IR,DR,RI> CR: 22000004 XER: 00000000
[ 16.918153] DAR: df98800a DSISR: 20000000
[ 16.918153] GPR00: c02f50dc e2449e50 c1140d00 e100dd24 c084b13c 00000008 c084b32b c016eb38
[ 16.918153] GPR08: c0850000 df988000 c0d10000 e2449eb0 22000288
[ 16.936695] NIP [c016eb8c] test_invalid_access+0x54/0x108
[ 16.942125] LR [c02f50dc] kunit_try_run_case+0x5c/0xd0
[ 16.947292] Call Trace:
[ 16.949746] [e2449e50] [c005a5ec] finish_task_switch.isra.0+0x54/0x23c (unreliable)
[ 16.957443] [e2449eb0] [c02f50dc] kunit_try_run_case+0x5c/0xd0
[ 16.963319] [e2449ed0] [c02f63ec] kunit_generic_run_threadfn_adapter+0x24/0x30
[ 16.970574] [e2449ef0] [c004e710] kthread+0x15c/0x174
[ 16.975670] [e2449f30] [c001317c] ret_from_kernel_thread+0x14/0x1c
[ 16.981896] Instruction dump:
[ 16.984879] 8129d608 38e7eb38 81020280 911f004c 39000000 995f0024 907f0028 90ff001c
[ 16.992710] 3949000a 915f0020 3d40c0d1 3d00c085 <8929000a> 3908adb0 812a4b98 3d40c02f
[ 17.000711] ==================================================================
[ 17.008223] # test_invalid_access: EXPECTATION FAILED at mm/kfence/kfence_test.c:636
[ 17.008223] Expected report_matches(&expect) to be true, but is false
[ 17.023243] not ok 21 - test_invalid_access