From: Barry Song <song.bao.hua@hisilicon.com>
To: <akpm@linux-foundation.org>, <linux-mm@kvack.org>,
<linux-kernel@vger.kernel.org>
Cc: linuxarm@huawei.com, "Barry Song" <song.bao.hua@hisilicon.com>,
"John Hubbard" <jhubbard@nvidia.com>, "Jan Kara" <jack@suse.cz>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
"Al Viro" <viro@zeniv.linux.org.uk>,
"Christoph Hellwig" <hch@infradead.org>,
"Dan Williams" <dan.j.williams@intel.com>,
"Dave Chinner" <david@fromorbit.com>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
"Jonathan Corbet" <corbet@lwn.net>,
"Michal Hocko" <mhocko@suse.com>,
"Mike Kravetz" <mike.kravetz@oracle.com>,
"Shuah Khan" <shuah@kernel.org>,
"Vlastimil Babka" <vbabka@suse.cz>
Subject: [PATCH] mm/gup: don't permit users to call get_user_pages with FOLL_LONGTERM
Date: Wed, 19 Aug 2020 23:01:00 +1200 [thread overview]
Message-ID: <20200819110100.23504-1-song.bao.hua@hisilicon.com> (raw)
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(-)
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
next reply other threads:[~2020-08-19 11:07 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-19 11:01 Barry Song [this message]
2020-08-19 17:44 ` [PATCH] mm/gup: don't permit users to call get_user_pages with FOLL_LONGTERM Ira Weiny
2020-08-19 18:14 ` John Hubbard
2020-09-03 7:12 ` Souptick Joarder
2020-09-03 7:23 ` John Hubbard
2020-09-03 18:39 ` Matthew Wilcox
2020-09-05 1:11 ` Souptick Joarder
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