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From: Souptick Joarder <jrdr.linux@gmail.com>
To: Ralph Campbell <rcampbell@nvidia.com>
Cc: Linux-MM <linux-mm@kvack.org>,
	linux-kernel@vger.kernel.org, John Hubbard <jhubbard@nvidia.com>,
	Ira Weiny <ira.weiny@intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Balbir Singh <bsingharora@gmail.com>,
	Dan Carpenter <dan.carpenter@oracle.com>,
	Matthew Wilcox <willy@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 4/5] mm/hmm: hmm_vma_fault() doesn't always call hmm_range_unregister()
Date: Thu, 9 May 2019 10:12:52 +0530	[thread overview]
Message-ID: <CAFqt6zbL1r6+G6f-4-cpktyNZ929d4tNfQDt4oHXqeHoC9chHw@mail.gmail.com> (raw)
In-Reply-To: <fa2078fd-3ec7-5503-94d7-c4d1a766029a@nvidia.com>

On Tue, May 7, 2019 at 11:42 PM Ralph Campbell <rcampbell@nvidia.com> wrote:
>
>
> On 5/7/19 6:15 AM, Souptick Joarder wrote:
> > On Tue, May 7, 2019 at 5:00 AM <rcampbell@nvidia.com> wrote:
> >>
> >> From: Ralph Campbell <rcampbell@nvidia.com>
> >>
> >> The helper function hmm_vma_fault() calls hmm_range_register() but is
> >> missing a call to hmm_range_unregister() in one of the error paths.
> >> This leads to a reference count leak and ultimately a memory leak on
> >> struct hmm.
> >>
> >> Always call hmm_range_unregister() if hmm_range_register() succeeded.
> >
> > How about * Call hmm_range_unregister() in error path if
> > hmm_range_register() succeeded* ?
>
> Sure, sounds good.
> I'll include that in v2.

Thanks.
>
> >>
> >> Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
> >> Cc: John Hubbard <jhubbard@nvidia.com>
> >> Cc: Ira Weiny <ira.weiny@intel.com>
> >> Cc: Dan Williams <dan.j.williams@intel.com>
> >> Cc: Arnd Bergmann <arnd@arndb.de>
> >> Cc: Balbir Singh <bsingharora@gmail.com>
> >> Cc: Dan Carpenter <dan.carpenter@oracle.com>
> >> Cc: Matthew Wilcox <willy@infradead.org>
> >> Cc: Souptick Joarder <jrdr.linux@gmail.com>
> >> Cc: Andrew Morton <akpm@linux-foundation.org>
> >> ---
> >>   include/linux/hmm.h | 3 ++-
> >>   1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/include/linux/hmm.h b/include/linux/hmm.h
> >> index 35a429621e1e..fa0671d67269 100644
> >> --- a/include/linux/hmm.h
> >> +++ b/include/linux/hmm.h
> >> @@ -559,6 +559,7 @@ static inline int hmm_vma_fault(struct hmm_range *range, bool block)
> >>                  return (int)ret;
> >>
> >>          if (!hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT)) {
> >> +               hmm_range_unregister(range);
> >>                  /*
> >>                   * The mmap_sem was taken by driver we release it here and
> >>                   * returns -EAGAIN which correspond to mmap_sem have been
> >> @@ -570,13 +571,13 @@ static inline int hmm_vma_fault(struct hmm_range *range, bool block)
> >>
> >>          ret = hmm_range_fault(range, block);
> >>          if (ret <= 0) {
> >> +               hmm_range_unregister(range);
> >
> > what is the reason to moved it up ?
>
> I moved it up because the normal calling pattern is:
>      down_read(&mm->mmap_sem)
>      hmm_vma_fault()
>          hmm_range_register()
>          hmm_range_fault()
>          hmm_range_unregister()
>      up_read(&mm->mmap_sem)
>
> I don't think it is a bug to unlock mmap_sem and then unregister,
> it is just more consistent nesting.

Ok. I think, adding it in change log will be helpful :)
>
> >>                  if (ret == -EBUSY || !ret) {
> >>                          /* Same as above, drop mmap_sem to match old API. */
> >>                          up_read(&range->vma->vm_mm->mmap_sem);
> >>                          ret = -EBUSY;
> >>                  } else if (ret == -EAGAIN)
> >>                          ret = -EBUSY;
> >> -               hmm_range_unregister(range);
> >>                  return ret;
> >>          }
> >>          return 0;
> >> --
> >> 2.20.1
> >>

  reply	other threads:[~2019-05-09  4:43 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-06 23:29 [PATCH 0/5] mm/hmm: HMM documentation updates and code fixes rcampbell
2019-05-06 23:29 ` [PATCH 1/5] mm/hmm: Update HMM documentation rcampbell
2019-06-06 14:02   ` Jason Gunthorpe
2019-06-06 18:50     ` Ralph Campbell
2019-06-06 19:32       ` Jason Gunthorpe
2019-05-06 23:29 ` [PATCH 2/5] mm/hmm: Clean up some coding style and comments rcampbell
2019-06-06 14:16   ` Jason Gunthorpe
2019-06-06 14:27     ` Jerome Glisse
2019-06-06 15:41       ` Jason Gunthorpe
2019-06-06 15:52         ` Jerome Glisse
2019-06-06 16:55           ` Joe Perches
2019-06-06 18:54           ` Jason Gunthorpe
2019-06-06 15:57   ` Jason Gunthorpe
2019-06-07  0:44     ` Ralph Campbell
2019-05-06 23:29 ` [PATCH 3/5] mm/hmm: Use mm_get_hmm() in hmm_range_register() rcampbell
2019-05-23 12:51   ` Jason Gunthorpe
2019-05-23 18:19     ` Ralph Campbell
2019-05-23 18:46     ` John Hubbard
2019-05-06 23:29 ` [PATCH 4/5] mm/hmm: hmm_vma_fault() doesn't always call hmm_range_unregister() rcampbell
2019-05-07 13:15   ` Souptick Joarder
2019-05-07 18:12     ` Ralph Campbell
2019-05-09  4:42       ` Souptick Joarder [this message]
2019-05-12 15:07       ` Jerome Glisse
2019-05-12 15:28         ` Jerome Glisse
2019-05-13 17:23         ` Ralph Campbell
2019-06-06 14:50   ` Jason Gunthorpe
2019-06-06 19:44     ` Ralph Campbell
2019-06-06 19:54       ` Jason Gunthorpe
2019-06-06 21:08         ` Ralph Campbell
2019-05-12 15:08 ` [PATCH 0/5] mm/hmm: HMM documentation updates and code fixes Jerome Glisse
2019-05-13 17:26   ` Ralph Campbell
2019-05-13 18:10     ` Jerome Glisse
2019-06-06 14:53 ` Jason Gunthorpe

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