On Sun, 2011-02-06 at 21:11 +0100, Jesper Juhl wrote:
> I believe that there's a small memory leak in
> drivers/pci/intel-iommu.c:get_domain_for_dev().
>
> If the call to alloc_domain() succeeds but the subsequent call to
> dmar_find_matched_drhd_unit() fails, then the current code will return
> NULL without calling domain_exit(domain) which will leak the memory that
> alloc_domain() allocated.
>
> The easy fix for that is to simply move the call to alloc_domain() below
> the call to dmar_find_matched_drhd_unit() since the latter does not depend
> on the former.
>
> I also made the change of moving the assignment to local variable 'iommu'
> below both calls since there is no point in doing that work if either of
> those those calls fail.
>
> I also changed the 'return NULL' in the dmar_find_matched_drhd_unit()
> failure case to a 'goto error' since I figured that if rechecking
> 'find_domain(pdev)' makes sense after a alloc_domain() failure then it
> would also make sense after a dmar_find_matched_drhd_unit() failure.
I don't think this change buys us anything. The goto error here seems
to be a hope that another cpu may have beat us and succeeded at
something we failed. In the case of matching the pci device to a drhd,
this should be deterministic (unless maybe we're racing a hot added
drhd). The rest seems fine to me. Thanks,
Alex
> Patch is only compile tested and I'm not very familliar with this code at
> all, so please review carefully before applying and please feel free to
> provide feedback if this patch is somehow not making sense.
>
> Signed-off-by: Jesper Juhl <jj@xxxxxxxxxxxxx>
> ---
> intel-iommu.c | 11 +++++------
> 1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
> index 4789f8e..dfbdb08 100644
> --- a/drivers/pci/intel-iommu.c
> +++ b/drivers/pci/intel-iommu.c
> @@ -1820,19 +1820,18 @@ static struct dmar_domain *get_domain_for_dev(struct pci_dev *pdev, int gaw)
> }
> }
>
> - domain = alloc_domain();
> - if (!domain)
> - goto error;
> -
> /* Allocate new domain for the device */
> drhd = dmar_find_matched_drhd_unit(pdev);
> if (!drhd) {
> printk(KERN_ERR "IOMMU: can't find DMAR for device %s\n",
> pci_name(pdev));
> - return NULL;
> + goto error;
> }
> - iommu = drhd->iommu;
> + domain = alloc_domain();
> + if (!domain)
> + goto error;
>
> + iommu = drhd->iommu;
> ret = iommu_attach_domain(domain, iommu);
> if (ret) {
> domain_exit(domain);
>
>
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