Messages in this thread | | | Subject | Re: [PATCH] mm/gup: don't permit users to call get_user_pages with FOLL_LONGTERM | From | John Hubbard <> | Date | Wed, 19 Aug 2020 11:14:55 -0700 |
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On 8/19/20 4:01 AM, Barry Song wrote: > gug prohibits users from calling get_user_pages() with FOLL_PIN. But it
Maybe Andrew can fix the typo above: gug --> gup.
> allows users to call get_user_pages() with FOLL_LONGTERM only. It seems > insensible. > > since FOLL_LONGTERM is a stricter case of FOLL_PIN, we should prohibit > users from calling get_user_pages() with FOLL_LONGTERM while not with > FOLL_PIN. > > mm/gup_benchmark.c used to be the only user who did this improperly. > But it has been fixed by moving to use pin_user_pages().
For future patches, you don't have to write everything in the commit log. Some things are better placed in a cover letter or after the "---" line, because they don't need to be recorded forever.
Anyway, the diffs seem fine, assuming that you've audited the call sites.
thanks, -- John Hubbard NVIDIA
> > Cc: John Hubbard <jhubbard@nvidia.com> > Cc: Jan Kara <jack@suse.cz> > Cc: Jérôme Glisse <jglisse@redhat.com> > Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org> > Cc: Al Viro <viro@zeniv.linux.org.uk> > Cc: Christoph Hellwig <hch@infradead.org> > Cc: Dan Williams <dan.j.williams@intel.com> > Cc: Dave Chinner <david@fromorbit.com> > Cc: Jason Gunthorpe <jgg@ziepe.ca> > Cc: Jonathan Corbet <corbet@lwn.net> > Cc: Michal Hocko <mhocko@suse.com> > Cc: Mike Kravetz <mike.kravetz@oracle.com> > Cc: Shuah Khan <shuah@kernel.org> > Cc: Vlastimil Babka <vbabka@suse.cz> > Signed-off-by: Barry Song <song.bao.hua@hisilicon.com> > --- > mm/gup.c | 37 ++++++++++++++++++++++--------------- > 1 file changed, 22 insertions(+), 15 deletions(-) > > diff --git a/mm/gup.c b/mm/gup.c > index ae096ea7583f..4da669f79566 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1789,6 +1789,25 @@ static long __get_user_pages_remote(struct mm_struct *mm, > gup_flags | FOLL_TOUCH | FOLL_REMOTE); > } > > +static bool is_valid_gup_flags(unsigned int gup_flags) > +{ > + /* > + * FOLL_PIN must only be set internally by the pin_user_pages*() APIs, > + * never directly by the caller, so enforce that with an assertion: > + */ > + if (WARN_ON_ONCE(gup_flags & FOLL_PIN)) > + return false; > + /* > + * FOLL_PIN is a prerequisite to FOLL_LONGTERM. Another way of saying > + * that is, FOLL_LONGTERM is a specific case, more restrictive case of > + * FOLL_PIN. > + */ > + if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM)) > + return false; > + > + return true; > +} > + > /** > * get_user_pages_remote() - pin user pages in memory > * @mm: mm_struct of target mm > @@ -1854,11 +1873,7 @@ long get_user_pages_remote(struct mm_struct *mm, > unsigned int gup_flags, struct page **pages, > struct vm_area_struct **vmas, int *locked) > { > - /* > - * FOLL_PIN must only be set internally by the pin_user_pages*() APIs, > - * never directly by the caller, so enforce that with an assertion: > - */ > - if (WARN_ON_ONCE(gup_flags & FOLL_PIN)) > + if (!is_valid_gup_flags(gup_flags)) > return -EINVAL; > > return __get_user_pages_remote(mm, start, nr_pages, gup_flags, > @@ -1904,11 +1919,7 @@ long get_user_pages(unsigned long start, unsigned long nr_pages, > unsigned int gup_flags, struct page **pages, > struct vm_area_struct **vmas) > { > - /* > - * FOLL_PIN must only be set internally by the pin_user_pages*() APIs, > - * never directly by the caller, so enforce that with an assertion: > - */ > - if (WARN_ON_ONCE(gup_flags & FOLL_PIN)) > + if (!is_valid_gup_flags(gup_flags)) > return -EINVAL; > > return __gup_longterm_locked(current->mm, start, nr_pages, > @@ -2810,11 +2821,7 @@ EXPORT_SYMBOL_GPL(get_user_pages_fast_only); > int get_user_pages_fast(unsigned long start, int nr_pages, > unsigned int gup_flags, struct page **pages) > { > - /* > - * FOLL_PIN must only be set internally by the pin_user_pages*() APIs, > - * never directly by the caller, so enforce that: > - */ > - if (WARN_ON_ONCE(gup_flags & FOLL_PIN)) > + if (!is_valid_gup_flags(gup_flags)) > return -EINVAL; > > /* >
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