Patch "[Variant 3/Meltdown] arm64: tls: Avoid unconditional zeroing of tpidrro_el0 for native tasks" has been added to the 4.14-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    [Variant 3/Meltdown] arm64: tls: Avoid unconditional zeroing of tpidrro_el0 for native tasks

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm64-tls-avoid-unconditional-zeroing-of-tpidrro_el0-for-native-tasks.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Wed Feb 14 14:44:54 CET 2018
From: Will Deacon <will.deacon@arm.com>
Date: Tue, 14 Nov 2017 14:33:28 +0000
Subject: [Variant 3/Meltdown] arm64: tls: Avoid unconditional zeroing of tpidrro_el0 for native tasks

From: Will Deacon <will.deacon@arm.com>


Commit 18011eac28c7 upstream.

When unmapping the kernel at EL0, we use tpidrro_el0 as a scratch register
during exception entry from native tasks and subsequently zero it in
the kernel_ventry macro. We can therefore avoid zeroing tpidrro_el0
in the context-switch path for native tasks using the entry trampoline.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Tested-by: Shanker Donthineni <shankerd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/arm64/kernel/process.c |   12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -314,16 +314,14 @@ void tls_preserve_current_state(void)
 
 static void tls_thread_switch(struct task_struct *next)
 {
-	unsigned long tpidr, tpidrro;
-
 	tls_preserve_current_state();
 
-	tpidr = *task_user_tls(next);
-	tpidrro = is_compat_thread(task_thread_info(next)) ?
-		  next->thread.tp_value : 0;
+	if (is_compat_thread(task_thread_info(next)))
+		write_sysreg(next->thread.tp_value, tpidrro_el0);
+	else if (!arm64_kernel_unmapped_at_el0())
+		write_sysreg(0, tpidrro_el0);
 
-	write_sysreg(tpidr, tpidr_el0);
-	write_sysreg(tpidrro, tpidrro_el0);
+	write_sysreg(*task_user_tls(next), tpidr_el0);
 }
 
 /* Restore the UAO state depending on next's addr_limit */


Patches currently in stable-queue which might be from will.deacon@arm.com are

queue-4.14/arm64-make-user_ds-an-inclusive-limit.patch
queue-4.14/arm64-mm-remove-pre_ttbr0_update_workaround-for-falkor-erratum-e1003.patch
queue-4.14/arm64-uaccess-don-t-bother-eliding-access_ok-checks-in-__-get-put-_user.patch
queue-4.14/arm64-cpufeature-pass-capability-structure-to-enable-callback.patch
queue-4.14/arm64-uaccess-mask-__user-pointers-for-__arch_-clear-copy_-_user.patch
queue-4.14/arm64-mm-add-arm64_kernel_unmapped_at_el0-helper.patch
queue-4.14/arm64-entry-reword-comment-about-post_ttbr_update_workaround.patch
queue-4.14/arm64-kaslr-put-kernel-vectors-address-in-separate-data-page.patch
queue-4.14/arm-arm64-smccc-make-function-identifiers-an-unsigned-quantity.patch
queue-4.14/arm64-move-bp-hardening-to-check_and_switch_context.patch
queue-4.14/arm-arm64-kvm-advertise-smccc-v1.1.patch
queue-4.14/arm64-move-post_ttbr_update_workaround-to-c-code.patch
queue-4.14/arm64-turn-on-kpti-only-on-cpus-that-need-it.patch
queue-4.14/firmware-psci-expose-psci-conduit.patch
queue-4.14/arm64-force-kpti-to-be-disabled-on-cavium-thunderx.patch
queue-4.14/arm64-entry-apply-bp-hardening-for-high-priority-synchronous-exceptions.patch
queue-4.14/arm64-kpti-fix-the-interaction-between-asid-switching-and-software-pan.patch
queue-4.14/firmware-psci-expose-smccc-version-through-psci_ops.patch
queue-4.14/arm64-mm-permit-transitioning-from-global-to-non-global-without-bbm.patch
queue-4.14/arm64-mm-allocate-asids-in-pairs.patch
queue-4.14/arm64-tls-avoid-unconditional-zeroing-of-tpidrro_el0-for-native-tasks.patch
queue-4.14/arm64-use-ret-instruction-for-exiting-the-trampoline.patch
queue-4.14/arm64-futex-mask-__user-pointers-prior-to-dereference.patch
queue-4.14/arm64-entry-explicitly-pass-exception-level-to-kernel_ventry-macro.patch
queue-4.14/arm64-implement-branch-predictor-hardening-for-affected-cortex-a-cpus.patch
queue-4.14/arm64-kpti-make-use-of-ng-dependent-on-arm64_kernel_unmapped_at_el0.patch
queue-4.14/arm-arm64-kvm-add-psci_version-helper.patch
queue-4.14/arm64-kill-psci_get_version-as-a-variant-2-workaround.patch
queue-4.14/arm64-entry-ensure-branch-through-syscall-table-is-bounded-under-speculation.patch
queue-4.14/arm64-mm-use-non-global-mappings-for-kernel-space.patch
queue-4.14/arm64-entry-apply-bp-hardening-for-suspicious-interrupts-from-el0.patch
queue-4.14/arm64-capabilities-handle-duplicate-entries-for-a-capability.patch
queue-4.14/arm64-entry-hook-up-entry-trampoline-to-exception-vectors.patch
queue-4.14/arm64-branch-predictor-hardening-for-cavium-thunderx2.patch
queue-4.14/arm64-uaccess-prevent-speculative-use-of-the-current-addr_limit.patch
queue-4.14/.arm64-add-software-workaround-for-falkor-erratum-1041.patch.swp
queue-4.14/arm64-use-pointer-masking-to-limit-uaccess-speculation.patch
queue-4.14/arm64-add-arm_smccc_arch_workaround_1-bp-hardening-support.patch
queue-4.14/arm64-erratum-work-around-falkor-erratum-e1003-in-trampoline-code.patch
queue-4.14/arm64-mm-fix-and-re-enable-arm64_sw_ttbr0_pan.patch
queue-4.14/arm64-mm-invalidate-both-kernel-and-user-asids-when-performing-tlbi.patch
queue-4.14/drivers-firmware-expose-psci_get_version-through-psci_ops-structure.patch
queue-4.14/arm64-mm-rename-post_ttbr0_update_workaround.patch
queue-4.14/arm64-mm-map-entry-trampoline-into-trampoline-and-kernel-page-tables.patch
queue-4.14/arm-arm64-kvm-turn-kvm_psci_version-into-a-static-inline.patch
queue-4.14/arm-arm64-kvm-implement-psci-1.0-support.patch
queue-4.14/arm64-move-task_-definitions-to-asm-processor.h.patch
queue-4.14/arm64-kconfig-reword-unmap_kernel_at_el0-kconfig-entry.patch
queue-4.14/arm64-mm-move-asid-from-ttbr0-to-ttbr1.patch
queue-4.14/arm64-mm-introduce-ttbr_asid_mask-for-getting-at-the-asid-in-the-ttbr.patch
queue-4.14/arm64-kvm-add-smccc_arch_workaround_1-fast-handling.patch
queue-4.14/arm64-take-into-account-id_aa64pfr0_el1.csv3.patch
queue-4.14/arm64-cputype-add-missing-midr-values-for-cortex-a72-and-cortex-a75.patch
queue-4.14/arm64-kvm-report-smccc_arch_workaround_1-bp-hardening-support.patch
queue-4.14/arm64-barrier-add-csdb-macros-to-control-data-value-prediction.patch
queue-4.14/arm-arm64-smccc-implement-smccc-v1.1-inline-primitive.patch
queue-4.14/arm64-implement-branch-predictor-hardening-for-falkor.patch
queue-4.14/arm64-kconfig-add-config_unmap_kernel_at_el0.patch
queue-4.14/arm64-add-software-workaround-for-falkor-erratum-1041.patch
queue-4.14/arm64-idmap-use-awx-flags-for-.idmap.text-.pushsection-directives.patch
queue-4.14/arm64-run-enable-method-for-errata-work-arounds-on-late-cpus.patch
queue-4.14/arm64-mm-temporarily-disable-arm64_sw_ttbr0_pan.patch
queue-4.14/arm64-entry-add-exception-trampoline-page-for-exceptions-from-el0.patch
queue-4.14/arm64-kvm-make-psci_version-a-fast-path.patch
queue-4.14/arm64-cpufeature-__this_cpu_has_cap-shouldn-t-stop-early.patch
queue-4.14/arm64-implement-array_index_mask_nospec.patch
queue-4.14/arm64-kpti-add-enable-callback-to-remap-swapper-using-ng-mappings.patch
queue-4.14/arm-arm64-kvm-consolidate-the-psci-include-files.patch
queue-4.14/arm64-add-skeleton-to-harden-the-branch-predictor-against-aliasing-attacks.patch
queue-4.14/arm64-define-cputype-macros-for-falkor-cpu.patch
queue-4.14/arm64-cpu_errata-add-kryo-to-falkor-1003-errata.patch
queue-4.14/arm-arm64-kvm-add-smccc-accessors-to-psci-code.patch
queue-4.14/arm64-entry-add-fake-cpu-feature-for-unmapping-the-kernel-at-el0.patch
queue-4.14/arm64-kvm-use-per-cpu-vector-when-bp-hardening-is-enabled.patch
queue-4.14/arm64-cputype-add-midr-values-for-cavium-thunderx2-cpus.patch
queue-4.14/arm64-kvm-increment-pc-after-handling-an-smc-trap.patch