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Message-ID: <20210406114153.GD96480@C02TD0UTHF1T.local>
Date: Tue, 6 Apr 2021 12:41:53 +0100
From: Mark Rutland <mark.rutland@....com>
To: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Kees Cook <keescook@...omium.org>,
Nathan Chancellor <nathan@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Masahiro Yamada <masahiroy@...nel.org>,
Will Deacon <will@...nel.org>, Jessica Yu <jeyu@...nel.org>,
Arnd Bergmann <arnd@...db.de>, Tejun Heo <tj@...nel.org>,
"Paul E. McKenney" <paulmck@...nel.org>,
Christoph Hellwig <hch@...radead.org>,
Peter Zijlstra <peterz@...radead.org>,
Sedat Dilek <sedat.dilek@...il.com>,
Catalin Marinas <catalin.marinas@....com>, bpf@...r.kernel.org,
linux-hardening@...r.kernel.org, linux-arch@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org,
linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
clang-built-linux@...glegroups.com
Subject: Re: [PATCH v5 13/18] arm64: use function_nocfi with __pa_symbol
On Thu, Apr 01, 2021 at 04:32:11PM -0700, Sami Tolvanen wrote:
> With CONFIG_CFI_CLANG, the compiler replaces function address
> references with the address of the function's CFI jump table
> entry. This means that __pa_symbol(function) returns the physical
> address of the jump table entry, which can lead to address space
> confusion as the jump table points to the function's virtual
> address. Therefore, use the function_nocfi() macro to ensure we are
> always taking the address of the actual function instead.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> Reviewed-by: Kees Cook <keescook@...omium.org>
> ---
> arch/arm64/include/asm/mmu_context.h | 2 +-
> arch/arm64/kernel/acpi_parking_protocol.c | 3 ++-
> arch/arm64/kernel/cpu-reset.h | 2 +-
> arch/arm64/kernel/cpufeature.c | 2 +-
> arch/arm64/kernel/psci.c | 3 ++-
> arch/arm64/kernel/smp_spin_table.c | 3 ++-
> 6 files changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
> index bd02e99b1a4c..386b96400a57 100644
> --- a/arch/arm64/include/asm/mmu_context.h
> +++ b/arch/arm64/include/asm/mmu_context.h
> @@ -140,7 +140,7 @@ static inline void cpu_replace_ttbr1(pgd_t *pgdp)
> ttbr1 |= TTBR_CNP_BIT;
> }
>
> - replace_phys = (void *)__pa_symbol(idmap_cpu_replace_ttbr1);
> + replace_phys = (void *)__pa_symbol(function_nocfi(idmap_cpu_replace_ttbr1));
>
> cpu_install_idmap();
> replace_phys(ttbr1);
> diff --git a/arch/arm64/kernel/acpi_parking_protocol.c b/arch/arm64/kernel/acpi_parking_protocol.c
> index e7c941d8340d..bfeeb5319abf 100644
> --- a/arch/arm64/kernel/acpi_parking_protocol.c
> +++ b/arch/arm64/kernel/acpi_parking_protocol.c
> @@ -99,7 +99,8 @@ static int acpi_parking_protocol_cpu_boot(unsigned int cpu)
> * that read this address need to convert this address to the
> * Boot-Loader's endianness before jumping.
> */
> - writeq_relaxed(__pa_symbol(secondary_entry), &mailbox->entry_point);
> + writeq_relaxed(__pa_symbol(function_nocfi(secondary_entry)),
> + &mailbox->entry_point);
> writel_relaxed(cpu_entry->gic_cpu_id, &mailbox->cpu_id);
>
> arch_send_wakeup_ipi_mask(cpumask_of(cpu));
> diff --git a/arch/arm64/kernel/cpu-reset.h b/arch/arm64/kernel/cpu-reset.h
> index ed50e9587ad8..f3adc574f969 100644
> --- a/arch/arm64/kernel/cpu-reset.h
> +++ b/arch/arm64/kernel/cpu-reset.h
> @@ -22,7 +22,7 @@ static inline void __noreturn cpu_soft_restart(unsigned long entry,
>
> unsigned long el2_switch = !is_kernel_in_hyp_mode() &&
> is_hyp_mode_available();
> - restart = (void *)__pa_symbol(__cpu_soft_restart);
> + restart = (void *)__pa_symbol(function_nocfi(__cpu_soft_restart));
>
> cpu_install_idmap();
> restart(el2_switch, entry, arg0, arg1, arg2);
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index e5281e1c8f1d..0b2e0d7b13ec 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -1462,7 +1462,7 @@ kpti_install_ng_mappings(const struct arm64_cpu_capabilities *__unused)
> if (arm64_use_ng_mappings)
> return;
>
> - remap_fn = (void *)__pa_symbol(idmap_kpti_install_ng_mappings);
> + remap_fn = (void *)__pa_symbol(function_nocfi(idmap_kpti_install_ng_mappings));
>
> cpu_install_idmap();
> remap_fn(cpu, num_online_cpus(), __pa_symbol(swapper_pg_dir));
> diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
> index 62d2bda7adb8..e74bcb57559b 100644
> --- a/arch/arm64/kernel/psci.c
> +++ b/arch/arm64/kernel/psci.c
> @@ -38,7 +38,8 @@ static int __init cpu_psci_cpu_prepare(unsigned int cpu)
>
> static int cpu_psci_cpu_boot(unsigned int cpu)
> {
> - int err = psci_ops.cpu_on(cpu_logical_map(cpu), __pa_symbol(secondary_entry));
> + int err = psci_ops.cpu_on(cpu_logical_map(cpu),
> + __pa_symbol(function_nocfi(secondary_entry)));
Could we use a temporary here, e.g.
phys_addr_t pa_secondary_entry = __pa_symbol(function_nocfi(secondary_entry));
int err = psci_ops.cpu_on(cpu_logical_map(cpu), pa_secondary_entry);
> if (err)
> pr_err("failed to boot CPU%d (%d)\n", cpu, err);
>
> diff --git a/arch/arm64/kernel/smp_spin_table.c b/arch/arm64/kernel/smp_spin_table.c
> index 056772c26098..4c4e36ded4aa 100644
> --- a/arch/arm64/kernel/smp_spin_table.c
> +++ b/arch/arm64/kernel/smp_spin_table.c
> @@ -88,7 +88,8 @@ static int smp_spin_table_cpu_prepare(unsigned int cpu)
> * boot-loader's endianness before jumping. This is mandated by
> * the boot protocol.
> */
> - writeq_relaxed(__pa_symbol(secondary_holding_pen), release_addr);
> + writeq_relaxed(__pa_symbol(function_nocfi(secondary_holding_pen)),
> + release_addr);
Likewise here? e.g. at the start of the function have:
phys_addr_t pa_holding_pen = __pa_symbol(function_nocfi(secondary_holding_pen));
... then here have:
writeq_relaxed(pa_holding_pen, release_addr);
With those:
Acked-by: Mark Rutland <mark.rutland@....com>
Thanks,
Mark.
> __flush_dcache_area((__force void *)release_addr,
> sizeof(*release_addr));
>
> --
> 2.31.0.208.g409f899ff0-goog
>
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