Re: [PATCH] iommu/dma: Fix MSI reservation allocation

On 03/03/2020 11:51 am, Marc Zyngier wrote:

The way cookie_init_hw_msi_region() allocates the iommu_dma_msi_page structures doesn't match the way iommu_put_dma_cookie() frees them.

The former performs a single allocation of all the required structures, while the latter tries to free them one at a time. It doesn't quite work for the main use case (the GICv3 ITS where the range is 64kB) when the base ganule size is 4kB.

This leads to a nice slab corruption on teardown, which is easily observable by simply creating a VF on a SRIOV-capable device, and tearing it down immediately (no need to even make use of it).

Fix it by allocating iommu_dma_msi_page structures one at a time.

Bleh, you know you're supposed to be using 64K pages on those things, right? :P

Fixes: 7c1b058c8b5a3 ("iommu/dma: Handle IOMMU API reserved regions") Signed-off-by: Marc Zyngier maz@kernel.org Cc: Robin Murphy robin.murphy@arm.com Cc: Joerg Roedel jroedel@suse.de Cc: Eric Auger eric.auger@redhat.com Cc: Will Deacon will@kernel.org Cc: stable@vger.kernel.org

---

drivers/iommu/dma-iommu.c | 36 ++++++++++++++++++++++++------------ 1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c index a2e96a5fd9a7..01fa64856c12 100644 --- a/drivers/iommu/dma-iommu.c +++ b/drivers/iommu/dma-iommu.c @@ -171,25 +171,37 @@ static int cookie_init_hw_msi_region(struct iommu_dma_cookie *cookie, phys_addr_t start, phys_addr_t end) { struct iova_domain *iovad = &cookie->iovad;

• struct iommu_dma_msi_page *msi_page;
• int i, num_pages;

• struct iommu_dma_msi_page *msi_page, *tmp;
• int i, num_pages, ret = 0;
• phys_addr_t base;

• start -= iova_offset(iovad, start);

• base = start -= iova_offset(iovad, start); num_pages = iova_align(iovad, end - start) >> iova_shift(iovad);

• msi_page = kcalloc(num_pages, sizeof(*msi_page), GFP_KERNEL);
• if (!msi_page)

• return -ENOMEM;
  

• for (i = 0; i < num_pages; i++) {

• msi_page[i].phys = start;
  

• msi_page[i].iova = start;
  

• INIT_LIST_HEAD(&msi_page[i].list);
  

• list_add(&msi_page[i].list, &cookie->msi_page_list);
  

• msi_page = kmalloc(sizeof(*msi_page), GFP_KERNEL);
  

• if (!msi_page) {
  

• 	ret = -ENOMEM;
  

I think we can just return here and skip the cleanup below - by the time we get here the cookie itself has already been allocated and initialised, so even if iommu_dma_init_domain() fails someone else has already accepted the responsibility of calling iommu_put_dma_cookie() at some point later, which will clean up properly.

Cheers, Robin.

• 	break;
  

• }
  

• msi_page->phys = start;
  

• msi_page->iova = start;
  

• INIT_LIST_HEAD(&msi_page->list);
  

• list_add(&msi_page->list, &cookie->msi_page_list);
  

  start += iovad->granule; }

• return 0;

• if (ret) {

• list_for_each_entry_safe(msi_page, tmp,
  

• 			 &cookie->msi_page_list, list) {
  

• 	if (msi_page->phys >= base && msi_page->phys < start) {
  

• 		list_del(&msi_page->list);
  

• 		kfree(msi_page);
  

• 	}
  

• }
  

• }
• return ret; }

static int iova_reserve_pci_windows(struct pci_dev *dev,