From: gyutrange wlsrbwjd643@naver.com
VNCR/TLBI VA reconstruction currently uses bit 48 as the sign bit, but for 48-bit virtual addresses the correct sign bit is bit 47. Using 48 can mis-canonicalize addresses in the negative half and may cause missed invalidations.
Although VNCR_EL2 encodes other architectural fields (RESS, BADDR; see Arm ARM D24.2.206), sign_extend64() interprets its second argument as the index of the sign bit. Passing 48 prevents propagation of the canonical sign bit for 48-bit VAs.
Impact: - Incorrect canonicalization of VAs with bit47=1 - Potential stale VNCR pseudo-TLB entries after TLBI or MMU notifier - Possible incorrect translation/permissions or DoS when combined with other issues
Fixes: 667304740537 ("KVM: arm64: Mask out non-VA bits from TLBI VA* on VNCR invalidation") Cc: stable@vger.kernel.org Reported-by: DongHa Lee gap-dev@example.com Reported-by: Gyujeong Jin wlsrbwjd7232@gmail.com Reported-by: Daehyeon Ko 4ncient@example.com Reported-by: Geonha Lee leegn4a@example.com Reported-by: Hyungyu Oh dqpc_lover@example.com Reported-by: Jaewon Yang r4mbb1@example.com Signed-off-by: Gyujeong Jin wlsrbwjd7232@gmail.com --- arch/arm64/kvm/nested.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c index 77db81bae86f..eaa6dd9da086 100644 --- a/arch/arm64/kvm/nested.c +++ b/arch/arm64/kvm/nested.c @@ -1169,7 +1169,7 @@ int kvm_vcpu_allocate_vncr_tlb(struct kvm_vcpu *vcpu)
static u64 read_vncr_el2(struct kvm_vcpu *vcpu) { - return (u64)sign_extend64(__vcpu_sys_reg(vcpu, VNCR_EL2), 48); + return (u64)sign_extend64(__vcpu_sys_reg(vcpu, VNCR_EL2), 47); }
static int kvm_translate_vncr(struct kvm_vcpu *vcpu)
On Mon, 01 Sep 2025 15:15:51 +0100, Gyujeong Jin wlsrbwjd7232@gmail.com wrote:
From: gyutrange wlsrbwjd643@naver.com
VNCR/TLBI VA reconstruction currently uses bit 48 as the sign bit, but for 48-bit virtual addresses the correct sign bit is bit 47.
No, that's not the case. Bit 55 is used at all times to determine which half of the address space a VA gets resolved from.
Using 48 can mis-canonicalize addresses in the negative half and may cause missed invalidations.
Although VNCR_EL2 encodes other architectural fields (RESS, BADDR; see Arm ARM D24.2.206), sign_extend64() interprets its second argument as the index of the sign bit. Passing 48 prevents propagation of the canonical sign bit for 48-bit VAs.
Impact:
- Incorrect canonicalization of VAs with bit47=1
No. We are not trying to make the VA canonical.
- Potential stale VNCR pseudo-TLB entries after TLBI or MMU notifier
No. The pseudo TLB is never created the first place.
- Possible incorrect translation/permissions or DoS when combined with other issues
Please explain, as "other issues" is not a valid argument.
Thanks,
M.
On Mon, Sep 01, 2025 at 11:15:51PM +0900, Gyujeong Jin wrote:
From: gyutrange wlsrbwjd643@naver.com
Does not match your signed-off-by line :(
On Mon, Sep 01, 2025 at 11:15:51PM +0900, Gyujeong Jin wrote:
From: gyutrange wlsrbwjd643@naver.com
VNCR/TLBI VA reconstruction currently uses bit 48 as the sign bit, but for 48-bit virtual addresses the correct sign bit is bit 47. Using 48 can mis-canonicalize addresses in the negative half and may cause missed invalidations.
Although VNCR_EL2 encodes other architectural fields (RESS, BADDR; see Arm ARM D24.2.206), sign_extend64() interprets its second argument as the index of the sign bit. Passing 48 prevents propagation of the canonical sign bit for 48-bit VAs.
Impact:
- Incorrect canonicalization of VAs with bit47=1
- Potential stale VNCR pseudo-TLB entries after TLBI or MMU notifier
- Possible incorrect translation/permissions or DoS when combined with other issues
Fixes: 667304740537 ("KVM: arm64: Mask out non-VA bits from TLBI VA* on VNCR invalidation") Cc: stable@vger.kernel.org Reported-by: DongHa Lee gap-dev@example.com Reported-by: Gyujeong Jin wlsrbwjd7232@gmail.com Reported-by: Daehyeon Ko 4ncient@example.com Reported-by: Geonha Lee leegn4a@example.com Reported-by: Hyungyu Oh dqpc_lover@example.com Reported-by: Jaewon Yang r4mbb1@example.com
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linux-stable-mirror@lists.linaro.org
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Greg KH -
Gyujeong Jin -
Marc Zyngier