Messages in this thread Patch in this message | | | From | alexander.levin@verizon ... | Subject | [PATCH AUTOSEL for 4.4 003/101] userfaultfd: shmem: __do_fault requires VM_FAULT_NOPAGE | Date | Thu, 7 Dec 2017 15:50:12 +0000 |
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From: Andrea Arcangeli <aarcange@redhat.com>
[ Upstream commit 6bbc4a4144b1a69743022ac68dfaf6e7d993abb9 ]
__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@redhat.com Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Reported-by: Dmitry Vyukov <dvyukov@google.com> Cc: "Kirill A. Shutemov" <kirill@shutemov.name> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <alexander.levin@verizon.com> --- fs/userfaultfd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 66cdb44616d5..59d58bdad7d3 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -386,7 +386,7 @@ int handle_userfault(struct vm_area_struct *vma, unsigned long address, * in such case. */ down_read(&mm->mmap_sem); - ret = 0; + ret = VM_FAULT_NOPAGE; } } -- 2.11.0
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