On 2016-07-14 07:21, Auger Eric wrote:
Hi Robin, Nate,
On 14/07/2016 12:36, Robin Murphy wrote:
On 14/07/16 09:34, Joerg Roedel wrote:
On Wed, Jul 13, 2016 at 02:49:32PM -0400, Nate Watterson wrote:
Passing a NULL or uninitialized iova_domain into put_iova_domain
will currently crash the kernel when the unconfigured iova_domain
data members are accessed. To prevent this from occurring, this
patch
adds a check to make sure that the domain is non-NULL and that the
domain granule is non-zero. The granule can be used to check if the
domain was properly initialized because calling init_iova_domain
with a granule of zero would have already triggered a BUG statement
crashing the kernel.
Have you seen real crashes happening because of this?
In my case, it was calling iommu_request_dm_for_dev() which triggered
the
"iommu_[get/put]_dma_cookie() without iommu_dma_init_domain()" issue
that
has Robin documented below.
I also saw the crash happening with my PCIe passthrough series (not
upstreamed)
[PATCH v10 0/8] [PATCH v10 0/8] KVM PCIe/MSI passthrough on ARM/ARM64:
kernel part 1/3: iommu changes https://lkml.org/lkml/2016/6/7/676
patch [PATCH v10 8/8] iommu/arm-smmu: get/put the msi cookie
also uses iommu_put_dma_cookie
and the uninitialised lock crash happens if the group gets destroyed
before the iommu_dma_init_domain is called, which can also happen for
me.
It _can_ happen via the iommu-dma code if something goes wrong
initialising a group - the IOVA domain gets allocated at the same time
as the default IOMMU domain, but isn't initialised until later once
the
device in question gets ity dma ops set up. If adding the device to
the
group fails, everything gets torn down again and
iommu_put_dma_cookie()
ends up trying to take an uninitialised lock .
Cant' we allow the granule check also with UNMANAGED type?
Thanks
Eric
However, I think the appropriate fix for that particular situation
would
be more like this:
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index ea5a9ebf0f78..d00d22930a6b 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -65,10 +65,11 @@ void iommu_put_dma_cookie(struct iommu_domain
*domain)
{
struct iova_domain *iovad = domain->iova_cookie;
- if (!iovad)
+ if (domain->type != IOMMU_DOMAIN_DMA || !iovad)
return;
- put_iova_domain(iovad);
+ if (iovad->granule)
+ put_iova_domain(iovad);
kfree(iovad);
domain->iova_cookie = NULL;
}
(It probably should have been that way from the start; mea culpa)
I originally put together a similar patch, but then thought that people
would
complain it didn't fix the root of the problem. Yet another instance
where
thinking was best avoided I guess.
Robin.
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