[PATCH] KVM: arm64: Correctly cap TLBI Range to the architural limit

[PATCH] KVM: arm64: Correctly cap TLBI Range to the architural limit

[Marc Zyngier]

TLB Invalidation by Range has a fairly powerful way of encoding pretty
large ranges in a small number of bits. This range can be based on an
arbitrary VA, which means it is pretty easy for a guest to generate an
overflow should the hypervisor be naive enough to add the range to the
base...

Make sure the range is capped to the limit dictated by the address bit
that determines the VA range. For an IPA invalidation, this is further
corrected down the line to ignore the upper range.

Fixes: 4ffa72ad8f37e ("KVM: arm64: nv: Add S1 TLB invalidation primitive for VNCR_EL2")
Reported-by: Wei-Lin Chang <weilin.chang@arm.com>
Link: https://lore.kernel.org/r/yifz3wn5gk5sr6mapi32trgk5m5kp33bquctsjmkifebnsnndt@fix6u4rthx4g
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
---
 arch/arm64/include/asm/kvm_nested.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
index c83be6d0e79ac..1ed7083358096 100644
--- a/arch/arm64/include/asm/kvm_nested.h
+++ b/arch/arm64/include/asm/kvm_nested.h
@@ -305,6 +305,12 @@ static inline u64 decode_range_tlbi(u64 val, u64 *range, u16 *asid)
 	num	= FIELD_GET(GENMASK(43, 39), val);
 	*range	= __TLBI_RANGE_PAGES(num, scale) << shift;
 
+	/* Cap the range to the correct half of the address space */
+	if (!(base & BIT(48)))
+		*range = min(*range, (BIT(48) - base));
+	else
+		*range = min(*range, ~base + 1);
+
 	return base;
 }
 
-- 
2.47.3

Re: [PATCH] KVM: arm64: Correctly cap TLBI Range to the architural limit

[Wei-Lin Chang]

On Mon, Aug 10, 2026 at 06:06:16PM +0100, Marc Zyngier wrote:
> TLB Invalidation by Range has a fairly powerful way of encoding pretty
> large ranges in a small number of bits. This range can be based on an
> arbitrary VA, which means it is pretty easy for a guest to generate an
> overflow should the hypervisor be naive enough to add the range to the
> base...
> 
> Make sure the range is capped to the limit dictated by the address bit
> that determines the VA range. For an IPA invalidation, this is further
> corrected down the line to ignore the upper range.
> 
> Fixes: 4ffa72ad8f37e ("KVM: arm64: nv: Add S1 TLB invalidation primitive for VNCR_EL2")
> Reported-by: Wei-Lin Chang <weilin.chang@arm.com>
> Link: https://lore.kernel.org/r/yifz3wn5gk5sr6mapi32trgk5m5kp33bquctsjmkifebnsnndt@fix6u4rthx4g
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> Cc: stable@vger.kernel.org
> ---
>  arch/arm64/include/asm/kvm_nested.h | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
> index c83be6d0e79ac..1ed7083358096 100644
> --- a/arch/arm64/include/asm/kvm_nested.h
> +++ b/arch/arm64/include/asm/kvm_nested.h
> @@ -305,6 +305,12 @@ static inline u64 decode_range_tlbi(u64 val, u64 *range, u16 *asid)
>  	num	= FIELD_GET(GENMASK(43, 39), val);
>  	*range	= __TLBI_RANGE_PAGES(num, scale) << shift;
>  
> +	/* Cap the range to the correct half of the address space */
> +	if (!(base & BIT(48)))
> +		*range = min(*range, (BIT(48) - base));
> +	else
> +		*range = min(*range, ~base + 1);
> +
>  	return base;
>  }

Reviewed-by: Wei-Lin Chang <weilin.chang@arm.com>

>  
> -- 
> 2.47.3
> 

Re: [PATCH] KVM: arm64: Correctly cap TLBI Range to the architural limit

[Oliver Upton]

On Mon, 10 Aug 2026 18:06:16 +0100, Marc Zyngier wrote:
> TLB Invalidation by Range has a fairly powerful way of encoding pretty
> large ranges in a small number of bits. This range can be based on an
> arbitrary VA, which means it is pretty easy for a guest to generate an
> overflow should the hypervisor be naive enough to add the range to the
> base...
> 
> Make sure the range is capped to the limit dictated by the address bit
> that determines the VA range. For an IPA invalidation, this is further
> corrected down the line to ignore the upper range.
> 
> [...]

Applied to next, thanks!

[1/1] KVM: arm64: Correctly cap TLBI Range to the architural limit
      https://git.kernel.org/kvmarm/kvmarm/c/69a598288195

--
Best,
Oliver