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SubjectRe: [PATCH v2 01/11] iommu/iova: Fix race between FQ timeout and teardown
On 10/12/2021 17:54, Robin Murphy wrote:
> From: Xiongfeng Wang<>
> It turns out to be possible for hotplugging out a device to reach the
> stage of tearing down the device's group and default domain before the
> domain's flush queue has drained naturally. At this point, it is then
> possible for the timeout to expire just*before* the del_timer() call

super nit: "just*before* the" - needs a whitespace before "before" :)

> from free_iova_flush_queue(), such that we then proceed to free the FQ
> resources while fq_flush_timeout() is still accessing them on another
> CPU. Crashes due to this have been observed in the wild while removing
> NVMe devices.
> Close the race window by using del_timer_sync() to safely wait for any
> active timeout handler to finish before we start to free things. We
> already avoid any locking in free_iova_flush_queue() since the FQ is
> supposed to be inactive anyway, so the potential deadlock scenario does
> not apply.
> Fixes: 9a005a800ae8 ("iommu/iova: Add flush timer")
> Signed-off-by: Xiongfeng Wang<>
> [ rm: rewrite commit message ]
> Signed-off-by: Robin Murphy<>


Reviewed-by: John Garry <>

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