From: Fuad Tabba <fuad.tabba@linux.dev>
To: Yuchao Zhang <ndaugoing@gmail.com>
Cc: sashiko-reviews@lists.linux.dev, kvmarm@lists.linux.dev,
Oliver Upton <oupton@kernel.org>, Marc Zyngier <maz@kernel.org>,
Fuad Tabba <tabba@google.com>
Subject: Re: [PATCH v2] KVM: selftests: arm64: Add test for cross-vCPU LPI disable race
Date: Tue, 22 Sep 2026 18:08:34 +0100 [thread overview]
Message-ID: <20260922170834.3228429-1-fuad.tabba@linux.dev> (raw)
In-Reply-To: <20260922105331.40498-1-ndaugoing@gmail.com>
Hi Yuchao,
The test passes on an unpatched 7.3-rc3 for me, so it doesn't reproduce
the bug yet.
On Tue, 22 Sep 2026 11:53:31 +0100, Yuchao Zhang <ndaugoing@gmail.com> wrote:
[...]
> On unpatched kernels, this race can lead to a use-after-free or host
> kernel panic in vgic_fold_lr_state() due to a dangling last_lr_irq
> pointer. With the fix in place (stopping the VM and holding a
> refcount on last_lr_irq), the test runs to completion without errors.
With only LPIs in flight EOIcount stays 0, so the fold breaks out of the
ap_list walk before it dereferences anything past the stale last_lr_irq.
To crash, the target vcpu has to EOI a non-LPI interrupt that's active
outside the LRs, with the remote disable landing while it's still in the
guest.
Cheers,
/fuad
next prev parent reply other threads:[~2026-09-22 17:08 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-18 4:02 [PATCH v2 0/1] KVM: arm64: vgic: fix UAF/crash on remote LPI disable zjamg
2026-09-18 4:02 ` [PATCH v2] KVM: arm64: vgic: Do not remove in-flight LPIs from AP list on disable zjamg
2026-09-18 7:22 ` Fuad Tabba
2026-09-18 11:50 ` Yuchao Zhang
2026-09-18 11:58 ` Fuad Tabba
2026-09-18 19:15 ` Oliver Upton
2026-09-20 23:54 ` Marc Zyngier
2026-09-20 1:49 ` [PATCH v3 0/1] KVM: arm64: vgic: Drop last_lr_irq and serialize overflow EOI replay Yuchao Zhang
2026-09-20 1:49 ` [PATCH v3] " Yuchao Zhang
2026-09-20 23:47 ` [PATCH v3 0/1] " Marc Zyngier
2026-09-22 10:16 ` Yuchao Zhang
2026-09-22 10:16 ` [PATCH] KVM: selftests: arm64: Add test for cross-vCPU LPI disable race Yuchao Zhang
2026-09-22 10:29 ` sashiko-bot
2026-09-22 10:53 ` Yuchao Zhang
2026-09-22 10:53 ` [PATCH v2] " Yuchao Zhang
2026-09-22 11:03 ` sashiko-bot
2026-09-22 11:24 ` Yuchao Zhang
2026-09-22 17:08 ` Fuad Tabba [this message]
2026-09-22 17:05 ` [PATCH v3 0/1] KVM: arm64: vgic: Drop last_lr_irq and serialize overflow EOI replay Fuad Tabba
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