On 2021-06-09 14:35, Xiyu Yang wrote:
> arm_smmu_rpm_get() invokes pm_runtime_get_sync(), which increases the
> refcount of the "smmu" even though the return value is less than 0.
>
> The reference counting issue happens in some error handling paths of
> arm_smmu_rpm_get() in its caller functions. When arm_smmu_rpm_get()
> fails, the caller functions forget to decrease the refcount of "smmu"
> increased by arm_smmu_rpm_get(), causing a refcount leak.
>
> Fix this issue by calling arm_smmu_rpm_put() or jumping to the "rpm_put"
> label when arm_smmu_rpm_get() fails.
If only there was some kind of helper function which could encapsulate
the correct expected behaviour in a single place...
In fact with the new pm_runtime_resume_and_get() API I think these two
patches boil down to a one-line change.
Thanks,
Robin.
> Signed-off-by: Xiyu Yang <[email protected]>
> Signed-off-by: Xin Tan <[email protected]>
> ---
> drivers/iommu/arm/arm-smmu/arm-smmu.c | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> index 6f72c4d208ca..177ee54c5534 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> @@ -840,7 +840,7 @@ static void arm_smmu_destroy_domain_context(struct iommu_domain *domain)
>
> ret = arm_smmu_rpm_get(smmu);
> if (ret < 0)
> - return;
> + goto rpm_put;
>
> /*
> * Disable the context bank and free the page tables before freeing
> @@ -857,6 +857,7 @@ static void arm_smmu_destroy_domain_context(struct iommu_domain *domain)
> free_io_pgtable_ops(smmu_domain->pgtbl_ops);
> __arm_smmu_free_bitmap(smmu->context_map, cfg->cbndx);
>
> +rpm_put:
> arm_smmu_rpm_put(smmu);
> }
>
> @@ -1153,7 +1154,7 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
>
> ret = arm_smmu_rpm_get(smmu);
> if (ret < 0)
> - return ret;
> + goto rpm_put;
>
> /* Ensure that the domain is finalised */
> ret = arm_smmu_init_domain_context(domain, smmu, dev);
> @@ -1404,7 +1405,7 @@ static struct iommu_device *arm_smmu_probe_device(struct device *dev)
>
> ret = arm_smmu_rpm_get(smmu);
> if (ret < 0)
> - goto out_cfg_free;
> + goto rpm_put;
>
> ret = arm_smmu_master_alloc_smes(dev);
> arm_smmu_rpm_put(smmu);
> @@ -1417,6 +1418,8 @@ static struct iommu_device *arm_smmu_probe_device(struct device *dev)
>
> return &smmu->iommu;
>
> +rpm_put:
> + arm_smmu_rpm_put(smmu);
> out_cfg_free:
> kfree(cfg);
> out_free:
> @@ -1438,8 +1441,10 @@ static void arm_smmu_release_device(struct device *dev)
> smmu = cfg->smmu;
>
> ret = arm_smmu_rpm_get(smmu);
> - if (ret < 0)
> + if (ret < 0) {
> + arm_smmu_rpm_put(smmu);
> return;
> + }
>
> arm_smmu_master_free_smes(cfg, fwspec);
>
>
Thanks for your advice, I'll send a v2 patch soon.
> -----Original Messages-----
> From: "Robin Murphy" <[email protected]>
> Sent Time: 2021-06-09 22:12:11 (Wednesday)
> To: "Xiyu Yang" <[email protected]>, "Will Deacon" <[email protected]>, "Joerg Roedel" <[email protected]>, "Nicolin Chen" <[email protected]>, "Bjorn Andersson" <[email protected]>, "Krishna Reddy" <[email protected]>, "Jordan Crouse" <[email protected]>, "Sai Prakash Ranjan" <[email protected]>, [email protected], [email protected], [email protected]
> Cc: [email protected], "Xin Tan" <[email protected]>
> Subject: Re: [PATCH] iommu/arm-smmu: Fix arm_smmu_device refcount leak when arm_smmu_rpm_get fails
>
> On 2021-06-09 14:35, Xiyu Yang wrote:
> > arm_smmu_rpm_get() invokes pm_runtime_get_sync(), which increases the
> > refcount of the "smmu" even though the return value is less than 0.
> >
> > The reference counting issue happens in some error handling paths of
> > arm_smmu_rpm_get() in its caller functions. When arm_smmu_rpm_get()
> > fails, the caller functions forget to decrease the refcount of "smmu"
> > increased by arm_smmu_rpm_get(), causing a refcount leak.
> >
> > Fix this issue by calling arm_smmu_rpm_put() or jumping to the "rpm_put"
> > label when arm_smmu_rpm_get() fails.
>
> If only there was some kind of helper function which could encapsulate
> the correct expected behaviour in a single place...
>
> In fact with the new pm_runtime_resume_and_get() API I think these two
> patches boil down to a one-line change.
>
> Thanks,
> Robin.
>
> > Signed-off-by: Xiyu Yang <[email protected]>
> > Signed-off-by: Xin Tan <[email protected]>
> > ---
> > drivers/iommu/arm/arm-smmu/arm-smmu.c | 13 +++++++++----
> > 1 file changed, 9 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > index 6f72c4d208ca..177ee54c5534 100644
> > --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > @@ -840,7 +840,7 @@ static void arm_smmu_destroy_domain_context(struct iommu_domain *domain)
> >
> > ret = arm_smmu_rpm_get(smmu);
> > if (ret < 0)
> > - return;
> > + goto rpm_put;
> >
> > /*
> > * Disable the context bank and free the page tables before freeing
> > @@ -857,6 +857,7 @@ static void arm_smmu_destroy_domain_context(struct iommu_domain *domain)
> > free_io_pgtable_ops(smmu_domain->pgtbl_ops);
> > __arm_smmu_free_bitmap(smmu->context_map, cfg->cbndx);
> >
> > +rpm_put:
> > arm_smmu_rpm_put(smmu);
> > }
> >
> > @@ -1153,7 +1154,7 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
> >
> > ret = arm_smmu_rpm_get(smmu);
> > if (ret < 0)
> > - return ret;
> > + goto rpm_put;
> >
> > /* Ensure that the domain is finalised */
> > ret = arm_smmu_init_domain_context(domain, smmu, dev);
> > @@ -1404,7 +1405,7 @@ static struct iommu_device *arm_smmu_probe_device(struct device *dev)
> >
> > ret = arm_smmu_rpm_get(smmu);
> > if (ret < 0)
> > - goto out_cfg_free;
> > + goto rpm_put;
> >
> > ret = arm_smmu_master_alloc_smes(dev);
> > arm_smmu_rpm_put(smmu);
> > @@ -1417,6 +1418,8 @@ static struct iommu_device *arm_smmu_probe_device(struct device *dev)
> >
> > return &smmu->iommu;
> >
> > +rpm_put:
> > + arm_smmu_rpm_put(smmu);
> > out_cfg_free:
> > kfree(cfg);
> > out_free:
> > @@ -1438,8 +1441,10 @@ static void arm_smmu_release_device(struct device *dev)
> > smmu = cfg->smmu;
> >
> > ret = arm_smmu_rpm_get(smmu);
> > - if (ret < 0)
> > + if (ret < 0) {
> > + arm_smmu_rpm_put(smmu);
> > return;
> > + }
> >
> > arm_smmu_master_free_smes(cfg, fwspec);
> >
> >