From: Vincenzo Frascino <vincenzo.frascino@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
Andrew Morton <akpm@linux-foundation.org>,
Will Deacon <will@kernel.org>, Dmitry Vyukov <dvyukov@google.com>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Alexander Potapenko <glider@google.com>,
Marco Elver <elver@google.com>,
Evgenii Stepanov <eugenis@google.com>,
Branislav Rankov <Branislav.Rankov@arm.com>,
Andrey Konovalov <andreyknvl@google.com>
Subject: Re: [PATCH v11 4/5] arm64: mte: Enable async tag check fault
Date: Fri, 5 Feb 2021 15:45:38 +0000 [thread overview]
Message-ID: <1254c150-599c-d39d-3b83-8af4f3c403ee@arm.com> (raw)
In-Reply-To: <20210205153918.GA12697@gaia>
On 2/5/21 3:39 PM, Catalin Marinas wrote:
> On Sat, Jan 30, 2021 at 04:52:24PM +0000, Vincenzo Frascino wrote:
>> diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
>> index 92078e1eb627..7763ac1f2917 100644
>> --- a/arch/arm64/kernel/mte.c
>> +++ b/arch/arm64/kernel/mte.c
>> @@ -182,6 +182,37 @@ bool mte_report_once(void)
>> return READ_ONCE(report_fault_once);
>> }
>>
>> +#ifdef CONFIG_KASAN_HW_TAGS
>> +void mte_check_tfsr_el1(void)
>> +{
>> + u64 tfsr_el1;
>> +
>> + if (!system_supports_mte())
>> + return;
>> +
>> + tfsr_el1 = read_sysreg_s(SYS_TFSR_EL1);
>> +
>> + /*
>> + * The kernel should never trigger an asynchronous fault on a
>> + * TTBR0 address, so we should never see TF0 set.
>> + * For futexes we disable checks via PSTATE.TCO.
>> + */
>> + WARN_ONCE(tfsr_el1 & SYS_TFSR_EL1_TF0,
>> + "Kernel async tag fault on TTBR0 address");
>
> Sorry, I got confused when I suggested this warning. If the user is
> running in async mode, the TFSR_EL1.TF0 bit may be set by
> copy_mount_options(), strncpy_from_user() which rely on an actual fault
> happening (not the case with asynchronous where only a bit is set). With
> the user MTE support, we never report asynchronous faults caused by the
> kernel on user addresses as we can't easily track them. So this warning
> may be triggered on correctly functioning kernel/user.
>
No issue, I will re-post removing the WARN_ONCE().
>> +
>> + if (unlikely(tfsr_el1 & SYS_TFSR_EL1_TF1)) {
>> + /*
>> + * Note: isb() is not required after this direct write
>> + * because there is no indirect read subsequent to it
>> + * (per ARM DDI 0487F.c table D13-1).
>> + */
>> + write_sysreg_s(0, SYS_TFSR_EL1);
>
> Zeroing the whole register is still fine, we don't care about the TF0
> bit anyway.
>
>> +
>> + kasan_report_async();
>> + }
>> +}
>> +#endif
>
--
Regards,
Vincenzo
next prev parent reply other threads:[~2021-02-05 23:13 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-30 16:52 [PATCH v11 0/5] arm64: ARMv8.5-A: MTE: Add async mode support Vincenzo Frascino
2021-01-30 16:52 ` [PATCH v11 1/5] arm64: mte: Add asynchronous " Vincenzo Frascino
2021-01-30 16:52 ` [PATCH v11 2/5] kasan: Add KASAN mode kernel parameter Vincenzo Frascino
2021-02-01 20:04 ` Andrey Konovalov
2021-02-05 15:49 ` Andrey Konovalov
2021-02-05 16:00 ` Vincenzo Frascino
2021-02-05 16:48 ` Will Deacon
2021-02-05 16:55 ` Vincenzo Frascino
2021-01-30 16:52 ` [PATCH v11 3/5] kasan: Add report for async mode Vincenzo Frascino
2021-01-30 16:52 ` [PATCH v11 4/5] arm64: mte: Enable async tag check fault Vincenzo Frascino
2021-02-05 15:39 ` Catalin Marinas
2021-02-05 15:45 ` Vincenzo Frascino [this message]
2021-01-30 16:52 ` [PATCH v11 5/5] kasan: don't run tests in async mode Vincenzo Frascino
2021-01-30 17:01 ` Vincenzo Frascino
2021-02-05 16:58 ` [PATCH v11 0/5] arm64: ARMv8.5-A: MTE: Add async mode support Vincenzo Frascino
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