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 <[email protected]> Cc: Jan Kara <[email protected]> Cc: Jérôme Glisse <[email protected]> Cc: "Matthew Wilcox (Oracle)" <[email protected]> Cc: Al Viro <[email protected]> Cc: Christoph Hellwig <[email protected]> Cc: Dan Williams <[email protected]> Cc: Dave Chinner <[email protected]> Cc: Jason Gunthorpe <[email protected]> Cc: Jonathan Corbet <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Mike Kravetz <[email protected]> Cc: Shuah Khan <[email protected]> Cc: Vlastimil Babka <[email protected]> Signed-off-by: Barry Song <[email protected]> --- 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
