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
WARNING: multiple messages have this Message-ID (diff)
From: Vincenzo Frascino <vincenzo.frascino@arm.com> To: Catalin Marinas <catalin.marinas@arm.com> Cc: Branislav Rankov <Branislav.Rankov@arm.com>, Marco Elver <elver@google.com>, Andrey Konovalov <andreyknvl@google.com>, Evgenii Stepanov <eugenis@google.com>, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, Alexander Potapenko <glider@google.com>, linux-arm-kernel@lists.infradead.org, Andrey Ryabinin <aryabinin@virtuozzo.com>, Andrew Morton <akpm@linux-foundation.org>, Will Deacon <will@kernel.org>, Dmitry Vyukov <dvyukov@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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-02-05 23:13 UTC|newest] Thread overview: 30+ 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 ` Vincenzo Frascino 2021-01-30 16:52 ` [PATCH v11 1/5] arm64: mte: Add asynchronous " Vincenzo Frascino 2021-01-30 16:52 ` Vincenzo Frascino 2021-01-30 16:52 ` [PATCH v11 2/5] kasan: Add KASAN mode kernel parameter Vincenzo Frascino 2021-01-30 16:52 ` Vincenzo Frascino 2021-02-01 20:04 ` Andrey Konovalov 2021-02-01 20:04 ` Andrey Konovalov 2021-02-05 15:49 ` Andrey Konovalov 2021-02-05 15:49 ` Andrey Konovalov 2021-02-05 16:00 ` Vincenzo Frascino 2021-02-05 16:00 ` Vincenzo Frascino 2021-02-05 16:48 ` Will Deacon 2021-02-05 16:48 ` Will Deacon 2021-02-05 16:55 ` Vincenzo Frascino 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 ` Vincenzo Frascino 2021-01-30 16:52 ` [PATCH v11 4/5] arm64: mte: Enable async tag check fault Vincenzo Frascino 2021-01-30 16:52 ` Vincenzo Frascino 2021-02-05 15:39 ` Catalin Marinas 2021-02-05 15:39 ` Catalin Marinas 2021-02-05 15:45 ` Vincenzo Frascino [this message] 2021-02-05 15:45 ` Vincenzo Frascino 2021-01-30 16:52 ` [PATCH v11 5/5] kasan: don't run tests in async mode Vincenzo Frascino 2021-01-30 16:52 ` Vincenzo Frascino 2021-01-30 17:01 ` 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 2021-02-05 16:58 ` Vincenzo Frascino
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