[PATCH 1/2] iommu/dma: Don't put uninitialised IOVA domains

[PATCH 1/2] iommu/dma: Don't put uninitialised IOVA domains

[Robin Murphy]

Due to the limitations of having to wait until we see a device's DMA
restrictions before we know how we want an IOVA domain initialised,
there is a window for error if a DMA ops domain is allocated but later
freed without ever being used. In that case, init_iova_domain() was
never called, so calling put_iova_domain() from iommu_put_dma_cookie()
ends up trying to take an uninitialised lock and crashing.

Make things robust by skipping the call unless the IOVA domain actually
has been initialised, as we probably should have done from the start.

Fixes: 0db2e5d18f76 ("iommu: Implement common IOMMU ops for DMA mapping")
Cc: stable@vger.kernel.org
Reported-by: Nate Watterson <nwatters@codeaurora.org>
Reviewed-by: Nate Watterson <nwatters@codeaurora.org>
Tested-by: Nate Watterson <nwatters@codeaurora.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
 drivers/iommu/dma-iommu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 08a1e2f3690f..7d991c81c4fa 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -68,7 +68,8 @@ void iommu_put_dma_cookie(struct iommu_domain *domain)
 	if (!iovad)
 		return;
 
-	put_iova_domain(iovad);
+	if (iovad->granule)
+		put_iova_domain(iovad);
 	kfree(iovad);
 	domain->iova_cookie = NULL;
 }
-- 
2.8.1.dirty

Re: [PATCH 1/2] iommu/dma: Don't put uninitialised IOVA domains

[Joerg Roedel]

On Tue, Aug 09, 2016 at 04:23:17PM +0100, Robin Murphy wrote:
> Due to the limitations of having to wait until we see a device's DMA
> restrictions before we know how we want an IOVA domain initialised,
> there is a window for error if a DMA ops domain is allocated but later
> freed without ever being used. In that case, init_iova_domain() was
> never called, so calling put_iova_domain() from iommu_put_dma_cookie()
> ends up trying to take an uninitialised lock and crashing.
> 
> Make things robust by skipping the call unless the IOVA domain actually
> has been initialised, as we probably should have done from the start.
> 
> Fixes: 0db2e5d18f76 ("iommu: Implement common IOMMU ops for DMA mapping")
> Cc: stable@vger.kernel.org
> Reported-by: Nate Watterson <nwatters@codeaurora.org>
> Reviewed-by: Nate Watterson <nwatters@codeaurora.org>
> Tested-by: Nate Watterson <nwatters@codeaurora.org>
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> Tested-by: Eric Auger <eric.auger@redhat.com>
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> ---
>  drivers/iommu/dma-iommu.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

Wow, that was quick :)

Applied to iommu/fixes, thanks.