From: Michael Bommarito <michael.bommarito@gmail•com>
To: Marc Zyngier <maz@kernel•org>, Oliver Upton <oupton@kernel•org>
Cc: Yao Yuan <yaoyuan@linux•alibaba.com>,
Joey Gouly <joey.gouly@arm•com>,
Suzuki K Poulose <suzuki.poulose@arm•com>,
Zenghui Yu <yuzenghui@huawei•com>,
Catalin Marinas <catalin.marinas@arm•com>,
Will Deacon <will@kernel•org>,
linux-arm-kernel@lists•infradead.org, kvmarm@lists•linux.dev,
linux-kernel@vger•kernel.org
Subject: [PATCH v2] KVM: arm64: vgic-its: reject restored DTE with out-of-range num_eventid_bits
Date: Tue, 19 May 2026 09:25:19 -0400 [thread overview]
Message-ID: <20260519132519.2142458-1-michael.bommarito@gmail.com> (raw)
In-Reply-To: <20260517174955.273004-1-michael.bommarito@gmail.com>
Userspace can restore an ITS Device Table Entry whose Size field encodes
more EventID bits than the virtual ITS supports. The live MAPD path
rejects that state, but vgic_its_restore_dte() accepts it and stores the
out-of-range value in dev->num_eventid_bits.
Reject restored DTEs with num_eventid_bits > VITS_TYPER_IDBITS before
allocating the device. This mirrors the MAPD check and prevents the
restored state from reaching vgic_its_restore_itt(), where the unchecked
value can be converted into an oversized scan_its_table() range.
Fixes: 57a9a117154c ("KVM: arm64: vgic-its: Device table save/restore")
Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Michael Bommarito <michael.bommarito@gmail•com>
---
Changes in v2:
- Trim the commit message to the root cause and fix.
- Shorten the in-code comment as suggested by Marc.
- Keep the validation logic unchanged.
arch/arm64/kvm/vgic/vgic-its.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c
index 2ea9f1c7ebcd0..1d7e5d560af4c 100644
--- a/arch/arm64/kvm/vgic/vgic-its.c
+++ b/arch/arm64/kvm/vgic/vgic-its.c
@@ -2307,6 +2307,10 @@ static int vgic_its_restore_dte(struct vgic_its *its, u32 id,
/* dte entry is valid */
offset = (entry & KVM_ITS_DTE_NEXT_MASK) >> KVM_ITS_DTE_NEXT_SHIFT;
+ /* Mimic the MAPD behaviour and reject invalid EID bits. */
+ if (num_eventid_bits > VITS_TYPER_IDBITS)
+ return -EINVAL;
+
if (!vgic_its_check_id(its, baser, id, NULL))
return -EINVAL;
--
2.53.0
next prev parent reply other threads:[~2026-05-19 13:25 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-17 17:49 [PATCH] KVM: arm64: vgic-its: reject restored DTE with out-of-range num_eventid_bits Michael Bommarito
2026-05-18 6:05 ` Yao Yuan
2026-05-18 8:23 ` Marc Zyngier
2026-05-20 6:04 ` Yao Yuan
2026-05-20 6:52 ` Marc Zyngier
2026-05-18 8:33 ` Marc Zyngier
2026-05-19 13:25 ` Michael Bommarito [this message]
2026-05-20 7:17 ` [PATCH v2] " Marc Zyngier
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