Messages in this thread | | | Date | Wed, 24 Mar 2021 16:20:27 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] userfaultfd/shmem: fix minor fault page leak |
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On Mon, 22 Mar 2021 13:48:35 -0700 Axel Rasmussen <axelrasmussen@google.com> wrote:
> This fix is analogous to Peter Xu's fix for hugetlb [0]. If we don't > put_page() after getting the page out of the page cache, we leak the > reference. > > The fix can be verified by checking /proc/meminfo and running the > userfaultfd selftest in shmem mode. Without the fix, we see MemFree / > MemAvailable steadily decreasing with each run of the test. With the > fix, memory is correctly freed after the test program exits. > > Fixes: 00da60b9d0a0 ("userfaultfd: support minor fault handling for shmem")
Confused. The affected code:
> --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -1831,6 +1831,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index, > > if (page && vma && userfaultfd_minor(vma)) { > unlock_page(page); > + put_page(page); > *fault_type = handle_userfault(vmf, VM_UFFD_MINOR); > return 0; > }
Is added by Peter's "page && vma && userfaultfd_minor". I assume that "Fixes:" is incorrect?
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