The patch titled
Subject: userfaultfd: shmem: __do_fault requires VM_FAULT_NOPAGE
has been added to the -mm tree. Its filename is
userfaultfd-shmem-__do_fault-requires-vm_fault_nopage.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/userfaultfd-shmem-__do_fault-requires-vm_fault_nopage.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/userfaultfd-shmem-__do_fault-requires-vm_fault_nopage.patch
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------------------------------------------------------
From: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Subject: userfaultfd: shmem: __do_fault requires VM_FAULT_NOPAGE
__do_fault assumes vmf->page has been initialized and is valid if
VM_FAULT_NOPAGE is not returned by vma->vm_ops->fault(vma, vmf).
handle_userfault() in turn should return VM_FAULT_NOPAGE if it doesn't
return VM_FAULT_SIGBUS or VM_FAULT_RETRY (the other two possibilities).
This VM_FAULT_NOPAGE case is only invoked when signal are pending and it
didn't matter for anonymous memory before. It only started to matter
since shmem was introduced. hugetlbfs also takes a different path and
doesn't exercise __do_fault.
Link: http://lkml.kernel.org/r/20170228154201.GH5816@xxxxxxxxxx
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/userfaultfd.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN fs/userfaultfd.c~userfaultfd-shmem-__do_fault-requires-vm_fault_nopage fs/userfaultfd.c
--- a/fs/userfaultfd.c~userfaultfd-shmem-__do_fault-requires-vm_fault_nopage
+++ a/fs/userfaultfd.c
@@ -489,7 +489,7 @@ int handle_userfault(struct vm_fault *vm
* in such case.
*/
down_read(&mm->mmap_sem);
- ret = 0;
+ ret = VM_FAULT_NOPAGE;
}
}
_
Patches currently in -mm which might be from aarcange@xxxxxxxxxx are
userfaultfd-shmem-__do_fault-requires-vm_fault_nopage.patch
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