On Tue, Feb 18, 2020 at 06:12:41PM +0000, Robin Murphy wrote:
> Currently, the implementation of qcom_iommu_domain_free() is guaranteed
> to do one of two things: WARN() and leak everything, or dereference NULL
> and crash. That alone is terrible, but in fact the whole idea of trying
> to track the liveness of a domain via the qcom_domain->iommu pointer as
> a sanity check is full of fundamentally flawed assumptions. Make things
> robust and actually functional by not trying to be quite so clever.
>
> Reported-by: Brian Masney <masneyb@xxxxxxxxxxxxx>
> Tested-by: Brian Masney <masneyb@xxxxxxxxxxxxx>
> Reported-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>
> Fixes: 0ae349a0f33f ("iommu/qcom: Add qcom_iommu")
> Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
This fixes the warning reported by Naresh Kamboju [1] for me. Thank you!
Tested-by: Stephan Gerhold <stephan@xxxxxxxxxxx>
[1]: https://lore.kernel.org/linux-arm-msm/CA+G9fYtScOpkLvx=__gP903uJ2v87RwZgkAuL6RpF9_DTDs9Zw@xxxxxxxxxxxxxx/
> ---
> drivers/iommu/qcom_iommu.c | 28 ++++++++++++----------------
> 1 file changed, 12 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/iommu/qcom_iommu.c b/drivers/iommu/qcom_iommu.c
> index 39759db4f003..4328da0b0a9f 100644
> --- a/drivers/iommu/qcom_iommu.c
> +++ b/drivers/iommu/qcom_iommu.c
> @@ -344,21 +344,19 @@ static void qcom_iommu_domain_free(struct iommu_domain *domain)
> {
> struct qcom_iommu_domain *qcom_domain = to_qcom_iommu_domain(domain);
>
> - if (WARN_ON(qcom_domain->iommu)) /* forgot to detach? */
> - return;
> -
> iommu_put_dma_cookie(domain);
>
> - /* NOTE: unmap can be called after client device is powered off,
> - * for example, with GPUs or anything involving dma-buf. So we
> - * cannot rely on the device_link. Make sure the IOMMU is on to
> - * avoid unclocked accesses in the TLB inv path:
> - */
> - pm_runtime_get_sync(qcom_domain->iommu->dev);
> -
> - free_io_pgtable_ops(qcom_domain->pgtbl_ops);
> -
> - pm_runtime_put_sync(qcom_domain->iommu->dev);
> + if (qcom_domain->iommu) {
> + /*
> + * NOTE: unmap can be called after client device is powered
> + * off, for example, with GPUs or anything involving dma-buf.
> + * So we cannot rely on the device_link. Make sure the IOMMU
> + * is on to avoid unclocked accesses in the TLB inv path:
> + */
> + pm_runtime_get_sync(qcom_domain->iommu->dev);
> + free_io_pgtable_ops(qcom_domain->pgtbl_ops);
> + pm_runtime_put_sync(qcom_domain->iommu->dev);
> + }
>
> kfree(qcom_domain);
> }
> @@ -404,7 +402,7 @@ static void qcom_iommu_detach_dev(struct iommu_domain *domain, struct device *de
> struct qcom_iommu_domain *qcom_domain = to_qcom_iommu_domain(domain);
> unsigned i;
>
> - if (!qcom_domain->iommu)
> + if (WARN_ON(!qcom_domain->iommu))
> return;
>
> pm_runtime_get_sync(qcom_iommu->dev);
> @@ -417,8 +415,6 @@ static void qcom_iommu_detach_dev(struct iommu_domain *domain, struct device *de
> ctx->domain = NULL;
> }
> pm_runtime_put_sync(qcom_iommu->dev);
> -
> - qcom_domain->iommu = NULL;
> }
>
> static int qcom_iommu_map(struct iommu_domain *domain, unsigned long iova,
> --
> 2.23.0.dirty
>
