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* [PATCH v2] KVM: arm64: Don't inherit exec permission across page-table levels
@ 2020-07-23 10:17 Will Deacon
  2020-07-23 17:09 ` Sasha Levin
  2020-07-28  9:37 ` Marc Zyngier
  0 siblings, 2 replies; 3+ messages in thread
From: Will Deacon @ 2020-07-23 10:17 UTC (permalink / raw)
  To: kvmarm; +Cc: Will Deacon, Marc Zyngier, stable, kernel-team, linux-arm-kernel

If a stage-2 page-table contains an executable, read-only mapping at the
pte level (e.g. due to dirty logging being enabled), a subsequent write
fault to the same page which tries to install a larger block mapping
(e.g. due to dirty logging having been disabled) will erroneously inherit
the exec permission and consequently skip I-cache invalidation for the
rest of the block.

Ensure that exec permission is only inherited by write faults when the
new mapping is of the same size as the existing one. A subsequent
instruction abort will result in I-cache invalidation for the entire
block mapping.

Cc: Marc Zyngier <maz@kernel.org>
Cc: <stable@vger.kernel.org>
Reviewed-by: Quentin Perret <qperret@google.com>
Tested-by: Quentin Perret <qperret@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
---

v2: Fix pte size check and allow inheriting to smaller granule.

 arch/arm64/kvm/mmu.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 8c0035cab6b6..31058e6e7c2a 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1326,7 +1326,7 @@ static bool stage2_get_leaf_entry(struct kvm *kvm, phys_addr_t addr,
 	return true;
 }
 
-static bool stage2_is_exec(struct kvm *kvm, phys_addr_t addr)
+static bool stage2_is_exec(struct kvm *kvm, phys_addr_t addr, unsigned long sz)
 {
 	pud_t *pudp;
 	pmd_t *pmdp;
@@ -1338,11 +1338,11 @@ static bool stage2_is_exec(struct kvm *kvm, phys_addr_t addr)
 		return false;
 
 	if (pudp)
-		return kvm_s2pud_exec(pudp);
+		return sz <= PUD_SIZE && kvm_s2pud_exec(pudp);
 	else if (pmdp)
-		return kvm_s2pmd_exec(pmdp);
+		return sz <= PMD_SIZE && kvm_s2pmd_exec(pmdp);
 	else
-		return kvm_s2pte_exec(ptep);
+		return sz == PAGE_SIZE && kvm_s2pte_exec(ptep);
 }
 
 static int stage2_set_pte(struct kvm *kvm, struct kvm_mmu_memory_cache *cache,
@@ -1958,7 +1958,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	 * execute permissions, and we preserve whatever we have.
 	 */
 	needs_exec = exec_fault ||
-		(fault_status == FSC_PERM && stage2_is_exec(kvm, fault_ipa));
+		(fault_status == FSC_PERM &&
+		 stage2_is_exec(kvm, fault_ipa, vma_pagesize));
 
 	if (vma_pagesize == PUD_SIZE) {
 		pud_t new_pud = kvm_pfn_pud(pfn, mem_type);
-- 
2.28.0.rc0.105.gf9edc3c819-goog

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^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH v2] KVM: arm64: Don't inherit exec permission across page-table levels
  2020-07-23 10:17 [PATCH v2] KVM: arm64: Don't inherit exec permission across page-table levels Will Deacon
@ 2020-07-23 17:09 ` Sasha Levin
  2020-07-28  9:37 ` Marc Zyngier
  1 sibling, 0 replies; 3+ messages in thread
From: Sasha Levin @ 2020-07-23 17:09 UTC (permalink / raw)
  To: Sasha Levin, Will Deacon, kvmarm; +Cc: Marc Zyngier, stable, linux-arm-kernel

Hi

[This is an automated email]

This commit has been processed because it contains a -stable tag.
The stable tag indicates that it's relevant for the following trees: all

The bot has tested the following trees: v5.7.10, v5.4.53, v4.19.134, v4.14.189, v4.9.231, v4.4.231.

v5.7.10: Build OK!
v5.4.53: Build OK!
v4.19.134: Failed to apply! Possible dependencies:
    3f58bf634555 ("KVM: arm/arm64: Share common code in user_mem_abort()")
    4ea5af531140 ("KVM: arm64: Support dirty page tracking for PUD hugepages")
    6396b852e46e ("KVM: arm/arm64: Re-factor setting the Stage 2 entry to exec on fault")
    7788a28062ac ("kvm: arm/arm64: Remove spurious WARN_ON")
    86d1c55ea605 ("KVM: arm64: Support PUD hugepage in stage2_is_exec()")
    b8e0ba7c8bea ("KVM: arm64: Add support for creating PUD hugepages at stage 2")
    e55cac5bf2a9 ("kvm: arm/arm64: Prepare for VM specific stage2 translations")
    f8df73388ee2 ("KVM: arm/arm64: Introduce helpers to manipulate page table entries")

v4.14.189: Failed to apply! Possible dependencies:
    0db9dd8a0fbd ("KVM: arm/arm64: Stop using the kernel's {pmd,pud,pgd}_populate helpers")
    17ab9d57deba ("KVM: arm/arm64: Drop vcpu parameter from guest cache maintenance operartions")
    3f58bf634555 ("KVM: arm/arm64: Share common code in user_mem_abort()")
    4ea5af531140 ("KVM: arm64: Support dirty page tracking for PUD hugepages")
    6396b852e46e ("KVM: arm/arm64: Re-factor setting the Stage 2 entry to exec on fault")
    86d1c55ea605 ("KVM: arm64: Support PUD hugepage in stage2_is_exec()")
    88dc25e8ea7c ("KVM: arm/arm64: Consolidate page-table accessors")
    91c703e0382a ("arm: KVM: Add optimized PIPT icache flushing")
    a15f693935a9 ("KVM: arm/arm64: Split dcache/icache flushing")
    a9c0e12ebee5 ("KVM: arm/arm64: Only clean the dcache on translation fault")
    d0e22b4ac3ba ("KVM: arm/arm64: Limit icache invalidation to prefetch aborts")
    f8df73388ee2 ("KVM: arm/arm64: Introduce helpers to manipulate page table entries")

v4.9.231: Failed to apply! Possible dependencies:
    0966253d7ccd ("kvm: arm64: Convert kvm_set_s2pte_readonly() from inline asm to cmpxchg()")
    0db9dd8a0fbd ("KVM: arm/arm64: Stop using the kernel's {pmd,pud,pgd}_populate helpers")
    13b7756cec3d ("arm/arm64: KVM: Stop propagating cacheability status of a faulted page")
    155433cb365e ("arm64: cache: Remove support for ASID-tagged VIVT I-caches")
    196f878a7ac2 ("KVM: arm/arm64: Signal SIGBUS when stage2 discovers hwpoison memory")
    3689c75af2a3 ("arm64: cpuinfo: remove I-cache VIPT aliasing detection")
    3bbf7157ac66 ("arm64: Convert pte handling from inline asm to using (cmp)xchg")
    3f58bf634555 ("KVM: arm/arm64: Share common code in user_mem_abort()")
    4ea5af531140 ("KVM: arm64: Support dirty page tracking for PUD hugepages")
    6396b852e46e ("KVM: arm/arm64: Re-factor setting the Stage 2 entry to exec on fault")
    6d332747fa5f ("arm64: Fix potential race with hardware DBM in ptep_set_access_flags()")
    73e86cb03cf2 ("arm64: Move PTE_RDONLY bit handling out of set_pte_at()")
    86d1c55ea605 ("KVM: arm64: Support PUD hugepage in stage2_is_exec()")
    87da236ebc71 ("arm64: KVM: Add support for VPIPT I-caches")
    88dc25e8ea7c ("KVM: arm/arm64: Consolidate page-table accessors")
    a15f693935a9 ("KVM: arm/arm64: Split dcache/icache flushing")
    b20d1ba3cf4b ("arm64: cpufeature: allow for version discrepancy in PMU implementations")
    b389d7997acb ("arm64: cpufeature: treat unknown fields as RES0")
    d0e22b4ac3ba ("KVM: arm/arm64: Limit icache invalidation to prefetch aborts")
    e7c600f149b8 ("arm64: hwpoison: add VM_FAULT_HWPOISON[_LARGE] handling")
    eab43e88734f ("arm64: cpufeature: Cleanup feature bit tables")
    f31deaadff0d ("arm64: cpufeature: Don't enforce system-wide SPE capability")
    f8df73388ee2 ("KVM: arm/arm64: Introduce helpers to manipulate page table entries")
    fe4fbdbcddea ("arm64: cpufeature: Track user visible fields")

v4.4.231: Failed to apply! Possible dependencies:
    06282fd2c2bf ("arm64: KVM: Implement vgic-v2 save/restore")
    064850532444 ("kvm: arm64: Enable hardware updates of the Access Flag for Stage 2 page tables")
    0db9dd8a0fbd ("KVM: arm/arm64: Stop using the kernel's {pmd,pud,pgd}_populate helpers")
    0f54b14e76f5 ("arm64: cpufeature: Change read_cpuid() to use sysreg's mrs_s macro")
    1431af367e52 ("arm64: KVM: Implement timer save/restore")
    20475f784d29 ("arm64: KVM: Add support for 16-bit VMID")
    35a2491a624a ("arm/arm64: KVM: Add hook for C-based stage2 init")
    3a3604bc5eb4 ("arm64: KVM: Switch to C-based stage2 init")
    406e308770a9 ("arm64: add ARMv8.2 id_aa64mmfr2 boiler plate")
    4ea5af531140 ("KVM: arm64: Support dirty page tracking for PUD hugepages")
    6d6ec20fcf28 ("arm64: KVM: Implement system register save/restore")
    8420dcd37ef3 ("arm: KVM: Make kvm_arm.h friendly to assembly code")
    86d1c55ea605 ("KVM: arm64: Support PUD hugepage in stage2_is_exec()")
    8eb992674c9e ("arm64: KVM: Implement debug save/restore")
    a563f7598198 ("arm64: Reuse TCR field definitions for EL1 and EL2")
    bbb3b6b35087 ("kvm-arm: Replace kvm_pmd_huge with pmd_thp_or_huge")
    c13d1683df16 ("arm64: KVM: Implement fpsimd save/restore")
    c76a0a6695c6 ("arm64: KVM: Add a HYP-specific header file")
    cb678d601651 ("arm64: kvm: 4.6-rc1: Fix VTCR_EL2 VS setting")
    d5370f754875 ("arm64: prefetch: add alternative pattern for CPUs without a prefetcher")
    f68d2b1b73cc ("arm64: KVM: Implement vgic-v3 save/restore")
    f8df73388ee2 ("KVM: arm/arm64: Introduce helpers to manipulate page table entries")


NOTE: The patch will not be queued to stable trees until it is upstream.

How should we proceed with this patch?

-- 
Thanks
Sasha
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH v2] KVM: arm64: Don't inherit exec permission across page-table levels
  2020-07-23 10:17 [PATCH v2] KVM: arm64: Don't inherit exec permission across page-table levels Will Deacon
  2020-07-23 17:09 ` Sasha Levin
@ 2020-07-28  9:37 ` Marc Zyngier
  1 sibling, 0 replies; 3+ messages in thread
From: Marc Zyngier @ 2020-07-28  9:37 UTC (permalink / raw)
  To: kvmarm, Will Deacon; +Cc: kernel-team, linux-arm-kernel, stable

On Thu, 23 Jul 2020 11:17:14 +0100, Will Deacon wrote:
> If a stage-2 page-table contains an executable, read-only mapping at the
> pte level (e.g. due to dirty logging being enabled), a subsequent write
> fault to the same page which tries to install a larger block mapping
> (e.g. due to dirty logging having been disabled) will erroneously inherit
> the exec permission and consequently skip I-cache invalidation for the
> rest of the block.
> 
> [...]

Applied to kvm-arm64/fixes-5.8-3, thanks!

[1/1] KVM: arm64: Don't inherit exec permission across page-table levels
      commit: b757b47a2fcba584d4a32fd7ee68faca510ab96f

Cheers,

	M.
-- 
Without deviation from the norm, progress is not possible.


_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

^ permalink raw reply	[flat|nested] 3+ messages in thread

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2020-07-23 10:17 [PATCH v2] KVM: arm64: Don't inherit exec permission across page-table levels Will Deacon
2020-07-23 17:09 ` Sasha Levin
2020-07-28  9:37 ` Marc Zyngier

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