| Message ID | 20200819110100.23504-1-song.bao.hua@hisilicon.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm/gup: don't permit users to call get_user_pages with FOLL_LONGTERM | expand |
On Wed, Aug 19, 2020 at 11:01:00PM +1200, Barry Song wrote: > gug prohibits users from calling get_user_pages() with FOLL_PIN. But it > 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(). > > 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> Seems reasonable to me. Reviewed-by: Ira Weiny <ira.weiny@intel.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; > > /* > -- > 2.27.0 > > >
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,
On Wed, Aug 19, 2020 at 11:45 PM John Hubbard <jhubbard@nvidia.com> wrote: > > 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. We can use is_valid_gup_flags() inside -> get_user_pages_locked(), get_user_pages_unlocked(), pin_user_pages_locked() as well. Are you planning to add it in future patches ? > > 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; > > > > /* > > > >
On 9/3/20 12:12 AM, Souptick Joarder wrote: > On Wed, Aug 19, 2020 at 11:45 PM John Hubbard <jhubbard@nvidia.com> wrote: >> >> 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. > > We can use is_valid_gup_flags() inside -> > get_user_pages_locked(), > get_user_pages_unlocked(), > pin_user_pages_locked() as well. Probably it's best to discern between valid pup flags, and valid gup flags. As in: separate functions for those. Maybe one is a subset of the other, but still. > > Are you planning to add it in future patches ? > It's not on my list. I don't see anything wrong with doing so, other than avoiding the minor pitfall I called out above. So if you want to do that, then feel free... thanks,
On Thu, Sep 03, 2020 at 12:42:44PM +0530, Souptick Joarder wrote: > We can use is_valid_gup_flags() inside -> > get_user_pages_locked(), > get_user_pages_unlocked(), > pin_user_pages_locked() as well. > > Are you planning to add it in future patches ? If you're looking for a new project, adding a foll_t or gup_t or something for the FOLL flags (like we have for gfp_t or vm_fault_t) would be helpful. We're inconsistent with our naming here.
On Fri, Sep 4, 2020 at 12:09 AM Matthew Wilcox <willy@infradead.org> wrote: > > On Thu, Sep 03, 2020 at 12:42:44PM +0530, Souptick Joarder wrote: > > We can use is_valid_gup_flags() inside -> > > get_user_pages_locked(), > > get_user_pages_unlocked(), > > pin_user_pages_locked() as well. > > > > Are you planning to add it in future patches ? > > If you're looking for a new project, adding a foll_t or gup_t or > something for the FOLL flags (like we have for gfp_t or vm_fault_t) > would be helpful. We're inconsistent with our naming here. Sure. I will start looking into this and come up with a RFC version.
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; /*
gug prohibits users from calling get_user_pages() with FOLL_PIN. But it 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(). 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(-)