From 0a9fabc941f67d30c54647cee272aad9d7aaf1a8 Mon Sep 17 00:00:00 2001 From: Barry Song Date: Tue, 13 Oct 2020 16:51:58 -0700 Subject: [PATCH] mm/gup: don't permit users to call get_user_pages with FOLL_LONGTERM MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit gup 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(). [akpm@linux-foundation.org: fix CONFIG_MMU=n build] Link: https://lkml.kernel.org/r/CA+G9fYuNS3k0DVT62twfV746pfNhCSrk5sVMcOcQ1PGGnEseyw@mail.gmail.com Signed-off-by: Barry Song Signed-off-by: Andrew Morton Reviewed-by: Ira Weiny Cc: John Hubbard Cc: Jan Kara Cc: Jérôme Glisse Cc: "Matthew Wilcox (Oracle)" Cc: Al Viro Cc: Christoph Hellwig Cc: Dan Williams Cc: Dave Chinner Cc: Jason Gunthorpe Cc: Jonathan Corbet Cc: Michal Hocko Cc: Mike Kravetz Cc: Shuah Khan Cc: Vlastimil Babka Cc: Naresh Kamboju Link: http://lkml.kernel.org/r/20200819110100.23504-1-song.bao.hua@hisilicon.com Signed-off-by: Linus Torvalds --- mm/gup.c | 37 ++++++++++++++++++++++--------------- 1 file changed, 22 insertions(+), 15 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index e869c634cc9a6..32d0e3ca7fbb2 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1747,6 +1747,25 @@ static __always_inline long __gup_longterm_locked(struct mm_struct *mm, } #endif /* CONFIG_FS_DAX || CONFIG_CMA */ +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; +} + #ifdef CONFIG_MMU static long __get_user_pages_remote(struct mm_struct *mm, unsigned long start, unsigned long nr_pages, @@ -1842,11 +1861,7 @@ 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, @@ -1892,11 +1907,7 @@ 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, @@ -2786,11 +2797,7 @@ 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; /* -- 2.39.5