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FAILED: patch "[PATCH] vfio/type1: Use follow_pte()" failed to apply to 4.4-stable tree

PATCH [email protected] 1 participant 1 message Mar 4, 2021

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The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 07956b6269d3ed05d854233d5bb776dca91751dd Mon Sep 17 00:00:00 2001
From: Alex Williamson <[email protected]>
Date: Tue, 16 Feb 2021 15:49:34 -0700
Subject: [PATCH] vfio/type1: Use follow_pte()

follow_pfn() doesn't make sure that we're using the correct page protections, get the pte with follow_pte() so that we can test protections and get the pfn from the pte.

Fixes 5cbf3264bc71 ("vfio/type1: Fix VA->PA translation for PFNMAP VMAs in vaddr_get_pfn()")
Reviewed-by Jason Gunthorpe <[email protected]>
Reviewed-by Cornelia Huck <[email protected]>
Reviewed-by Peter Xu <[email protected]>
Signed-off-by Alex Williamson <[email protected]>
drivers/vfio/vfio_iommu_type1.c +13 -2
index b3df383d7028..ed03f3fcb07e 100644
@@ -24,6 +24,7 @@
 #include <linux/compat.h>
 #include <linux/device.h>
 #include <linux/fs.h>
+#include <linux/highmem.h>
 #include <linux/iommu.h>
 #include <linux/module.h>
 #include <linux/mm.h>

@@ -462,9 +463,11 @@ static int follow_fault_pfn(struct vm_area_struct *vma, struct mm_struct *mm,
 			    unsigned long vaddr, unsigned long *pfn,
 			    bool write_fault)
 {
+	pte_t *ptep;
+	spinlock_t *ptl;
 	int ret;
 
-	ret = follow_pfn(vma, vaddr, pfn);
+	ret = follow_pte(vma->vm_mm, vaddr, &ptep, &ptl);
 	if (ret) {
 		bool unlocked = false;
 

@@ -478,9 +481,17 @@ static int follow_fault_pfn(struct vm_area_struct *vma, struct mm_struct *mm,
 		if (ret)
 			return ret;
 
-		ret = follow_pfn(vma, vaddr, pfn);
+		ret = follow_pte(vma->vm_mm, vaddr, &ptep, &ptl);
+		if (ret)
+			return ret;
 	}
 
+	if (write_fault && !pte_write(*ptep))
+		ret = -EFAULT;
+	else
+		*pfn = pte_pfn(*ptep);
+
+	pte_unmap_unlock(ptep, ptl);
 	return ret;
 }