Re: [patch] iommu/vt-d: shift wrapping bug in prq_event_thread()

[Woodhouse, David]

On Thu, 2015-10-15 at 21:25 +0300, Dan Carpenter wrote:
> The "req->addr" variable is a bit field declared as "u64 addr:52;".
> The "address" variable is a u64.  We need to cast "req->addr" to a u64
> before the shift or the result is truncated to 52 bits.
> 
> Fixes: 0b9252a34858 ('iommu/vt-d: Implement page request handling')
> Signed-off-by: Dan Carpenter 

Applied; thanks.

> Also does this code work if PAGE_SHIFT is more than 12?  (I am a newbie
> so this is not rhetorical, I don't know the answer).

Er, no it doesn't. That should have been VTD_PAGE_SHIFT, not PAGE_SHIFT
— and then it *will* always be 12. Thanks for pointing it out.

-- 
David WoodhouseOpen Source Technology Centre
david.woodho...@intel.com  Intel Corporation



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[patch] iommu/vt-d: shift wrapping bug in prq_event_thread()

[Dan Carpenter]

The "req->addr" variable is a bit field declared as "u64 addr:52;".
The "address" variable is a u64.  We need to cast "req->addr" to a u64
before the shift or the result is truncated to 52 bits.

Fixes: 0b9252a34858 ('iommu/vt-d: Implement page request handling')
Signed-off-by: Dan Carpenter 
---
Also does this code work if PAGE_SHIFT is more than 12?  (I am a newbie
so this is not rhetorical, I don't know the answer).

diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
index ba9..19aa67b 100644
--- a/drivers/iommu/intel-svm.c
+++ b/drivers/iommu/intel-svm.c
@@ -395,7 +395,7 @@ static irqreturn_t prq_event_thread(int irq, void *d)
req = >prq[head / sizeof(*req)];
 
result = QI_RESP_INVALID;
-   address = req->addr << PAGE_SHIFT;
+   address = (u64)req->addr << PAGE_SHIFT;
if (!req->pasid_present) {
pr_err("%s: Page request without PASID: %08llx 
%08llx\n",
   iommu->name, ((unsigned long long *)req)[0],
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