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Subject[PATCH] userfaultfd: mcopy_atomic: update cases returning -ENOENT
Hello Andrew,

The patch below is an incremental fixup for concerns Andrea raised at [1].
Please let me know if you prefer me to update the original patch and
resend.

[1] http://www.spinics.net/lists/linux-mm/msg121267.html

--
Sincerely yours,
Mike.

From 8acff65ecee8ca4cc892d35b45125c34568d1c93 Mon Sep 17 00:00:00 2001
From: Mike Rapoport <rppt@linux.vnet.ibm.com>
Date: Tue, 7 Feb 2017 11:50:17 +0200
Subject: [PATCH] userfaultfd: mcopy_atomic: update cases returning -ENOENT

As Andrea commented in [1], if the VMA covering the address was unmapped,
we may end up with a VMA a way above the faulting address. In this case we
would like to return -ENOENT to allow uffd monitor detection of VMA
removal.

[1] http://www.spinics.net/lists/linux-mm/msg121267.html

Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
---
mm/userfaultfd.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index b861cf9..cf43456 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -206,6 +206,10 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
if (!dst_vma->vm_userfaultfd_ctx.ctx)
goto out_unlock;

+ if (dst_start < dst_vma->vm_start ||
+ dst_start + len > dst_vma->vm_end)
+ goto out_unlock;
+
err = -EINVAL;
if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
goto out_unlock;
@@ -216,9 +220,6 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
*/
if (dst_vma->vm_flags & VM_SHARED)
goto out_unlock;
- if (dst_start < dst_vma->vm_start ||
- dst_start + len > dst_vma->vm_end)
- goto out_unlock;
}

if (WARN_ON(dst_addr & (vma_hpagesize - 1) ||
@@ -385,13 +386,14 @@ static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
if (!dst_vma->vm_userfaultfd_ctx.ctx)
goto out_unlock;

- err = -EINVAL;
- if (!vma_is_shmem(dst_vma) && dst_vma->vm_flags & VM_SHARED)
- goto out_unlock;
if (dst_start < dst_vma->vm_start ||
dst_start + len > dst_vma->vm_end)
goto out_unlock;

+ err = -EINVAL;
+ if (!vma_is_shmem(dst_vma) && dst_vma->vm_flags & VM_SHARED)
+ goto out_unlock;
+
/*
* If this is a HUGETLB vma, pass off to appropriate routine
*/
--
1.9.1
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