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authorAndrea Arcangeli <aarcange@redhat.com>2017-03-10 03:17:11 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2017-03-10 04:01:10 +0300
commit70ccb92fdd90b35bb6f9200093d4ffd6cb38156b (patch)
tree1a010b4c126bf64c0a740f648b96050d4b122d68 /include
parent7eb76d457fd758d396bc2e65cb0ace5aae614149 (diff)
downloadlinux-70ccb92fdd90b35bb6f9200093d4ffd6cb38156b.tar.xz
userfaultfd: non-cooperative: userfaultfd_remove revalidate vma in MADV_DONTNEED
userfaultfd_remove() has to be execute before zapping the pagetables or UFFDIO_COPY could keep filling pages after zap_page_range returned, which would result in non zero data after a MADV_DONTNEED. However userfaultfd_remove() may have to release the mmap_sem. This was handled correctly in MADV_REMOVE, but MADV_DONTNEED accessed a potentially stale vma (the very vma passed to zap_page_range(vma, ...)). The fix consists in revalidating the vma in case userfaultfd_remove() had to release the mmap_sem. This also optimizes away an unnecessary down_read/up_read in the MADV_REMOVE case if UFFD_EVENT_FORK had to be delivered. It all remains zero runtime cost in case CONFIG_USERFAULTFD=n as userfaultfd_remove() will be defined as "true" at build time. Link: http://lkml.kernel.org/r/20170302173738.18994-3-aarcange@redhat.com Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Acked-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/userfaultfd_k.h7
1 files changed, 3 insertions, 4 deletions
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index f2b79bf4c895..48a3483dccb1 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -61,8 +61,7 @@ extern void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *,
unsigned long from, unsigned long to,
unsigned long len);
-extern void userfaultfd_remove(struct vm_area_struct *vma,
- struct vm_area_struct **prev,
+extern bool userfaultfd_remove(struct vm_area_struct *vma,
unsigned long start,
unsigned long end);
@@ -118,11 +117,11 @@ static inline void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *ctx,
{
}
-static inline void userfaultfd_remove(struct vm_area_struct *vma,
- struct vm_area_struct **prev,
+static inline bool userfaultfd_remove(struct vm_area_struct *vma,
unsigned long start,
unsigned long end)
{
+ return true;
}
static inline int userfaultfd_unmap_prep(struct vm_area_struct *vma,