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Subject[PATCH 4/4] iommu/vt-d: Do access checks before calling handle_mm_fault()
Date
From: Joerg Roedel <jroedel@suse.de>

Not doing so is a bug and might trigger a BUG_ON in
handle_mm_fault(). So add the proper permission checks
before calling into mm code.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
drivers/iommu/intel-svm.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)

diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
index c69e3f9..5046483 100644
--- a/drivers/iommu/intel-svm.c
+++ b/drivers/iommu/intel-svm.c
@@ -484,6 +484,23 @@ struct page_req_dsc {
};

#define PRQ_RING_MASK ((0x1000 << PRQ_ORDER) - 0x10)
+
+static bool access_error(struct vm_area_struct *vma, struct page_req_dsc *req)
+{
+ unsigned long requested = 0;
+
+ if (req->exe_req)
+ requested |= VM_EXEC;
+
+ if (req->rd_req)
+ requested |= VM_READ;
+
+ if (req->wr_req)
+ requested |= VM_WRITE;
+
+ return (requested & ~vma->vm_flags) != 0;
+}
+
static irqreturn_t prq_event_thread(int irq, void *d)
{
struct intel_iommu *iommu = d;
@@ -539,6 +556,9 @@ static irqreturn_t prq_event_thread(int irq, void *d)
if (!vma || address < vma->vm_start)
goto invalid;

+ if (access_error(vma, req))
+ goto invalid;
+
ret = handle_mm_fault(svm->mm, vma, address,
req->wr_req ? FAULT_FLAG_WRITE : 0);
if (ret & VM_FAULT_ERROR)
--
1.9.1


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