[PATCH 4.4 77/88] mm: replace get_user_pages_locked() write/force parameters with gup_flags

Greg Kroah-Hartman
2018-12-14T12:16:33Z

From: Lorenzo Stoakes <lstoakes@gmail.com>

commit 3b913179c3fa89dd0e304193fa0c746fc0481447 upstream.

This removes the 'write' and 'force' use from get_user_pages_locked()
and replaces them with 'gup_flags' to make the use of FOLL_FORCE
explicit in callers as use of this flag can result in surprising
behaviour (and hence bugs) within the mm subsystem.

Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 4.4: adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/mm.h | 3 +--
mm/frame_vector.c | 8 +++++++-
mm/gup.c | 12 +++---------
mm/nommu.c | 5 ++++-
4 files changed, 15 insertions(+), 13 deletions(-)

--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1203,8 +1203,7 @@ long get_user_pages(struct task_struct *
struct vm_area_struct **vmas);
long get_user_pages_locked(struct task_struct *tsk, struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
- int write, int force, struct page **pages,
- int *locked);
+ unsigned int gup_flags, struct page **pages, int *locked);
long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
struct page **pages, unsigned int gup_flags);
--- a/mm/frame_vector.c
+++ b/mm/frame_vector.c
@@ -41,10 +41,16 @@ int get_vaddr_frames(unsigned long start
int ret = 0;
int err;
int locked;
+ unsigned int gup_flags = 0;

if (nr_frames == 0)
return 0;

+ if (write)
+ gup_flags |= FOLL_WRITE;
+ if (force)
+ gup_flags |= FOLL_FORCE;
+
if (WARN_ON_ONCE(nr_frames > vec->nr_allocated))
nr_frames = vec->nr_allocated;

@@ -59,7 +65,7 @@ int get_vaddr_frames(unsigned long start
vec->got_ref = true;
vec->is_pfns = false;
ret = get_user_pages_locked(current, mm, start, nr_frames,
- write, force, (struct page **)(vec->ptrs), &locked);
+ gup_flags, (struct page **)(vec->ptrs), &locked);
goto out;
}

--- a/mm/gup.c
+++ b/mm/gup.c
@@ -737,18 +737,12 @@ static __always_inline long __get_user_p
*/
long get_user_pages_locked(struct task_struct *tsk, struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
- int write, int force, struct page **pages,
+ unsigned int gup_flags, struct page **pages,
int *locked)
{
- unsigned int flags = FOLL_TOUCH;
-
- if (write)
- flags |= FOLL_WRITE;
- if (force)
- flags |= FOLL_FORCE;
-
return __get_user_pages_locked(tsk, mm, start, nr_pages,
- pages, NULL, locked, true, flags);
+ pages, NULL, locked, true,
+ gup_flags | FOLL_TOUCH);
}
EXPORT_SYMBOL(get_user_pages_locked);

--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -201,9 +201,12 @@ EXPORT_SYMBOL(get_user_pages);

long get_user_pages_locked(struct task_struct *tsk, struct mm_struct *mm,
unsigned long start, unsigned long nr_pages,
- int write, int force, struct page **pages,
+ unsigned int gup_flags, struct page **pages,
int *locked)
{
+ int write = gup_flags & FOLL_WRITE;
+ int force = gup_flags & FOLL_FORCE;
+
return get_user_pages(tsk, mm, start, nr_pages, write, force,
pages, NULL);
}