From: Andrew Morton <akpm@linux-foundation.org>
To: Axel Rasmussen <axelrasmussen@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
Andrea Arcangeli <aarcange@redhat.com>,
Hugh Dickins <hughd@google.com>,
Jerome Glisse <jglisse@redhat.com>, Joe Perches <joe@perches.com>,
Lokesh Gidra <lokeshgidra@google.com>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Peter Xu <peterx@redhat.com>, Shaohua Li <shli@fb.com>,
Shuah Khan <shuah@kernel.org>, Wang Qing <wangqing@vivo.com>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-kselftest@vger.kernel.org,
Brian Geffon <bgeffon@google.com>,
Cannon Matthews <cannonmatthews@google.com>,
"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
David Rientjes <rientjes@google.com>,
Michel Lespinasse <walken@google.com>,
Mina Almasry <almasrymina@google.com>,
Oliver Upton <oupton@google.com>
Subject: Re: [PATCH] userfaultfd/shmem: fix minor fault page leak
Date: Wed, 24 Mar 2021 16:20:27 -0700 [thread overview]
Message-ID: <20210324162027.cc723b545ff62b1ad6f5223e@linux-foundation.org> (raw)
In-Reply-To: <20210322204836.1650221-1-axelrasmussen@google.com>
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?
next prev parent reply other threads:[~2021-03-24 23:20 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-22 20:48 [PATCH] userfaultfd/shmem: fix minor fault page leak Axel Rasmussen
2021-03-22 21:00 ` Peter Xu
2021-03-24 23:20 ` Andrew Morton [this message]
2021-03-25 0:52 ` Peter Xu
2021-03-25 2:10 ` Axel Rasmussen
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