[PATCH 4.4 74/88] mm: remove write/force parameters from __get_user_pages_locked()

Greg Kroah-Hartman
2018-12-14T12:16:24Z

From: Lorenzo Stoakes <lstoakes@gmail.com>

commit 859110d7497cdd0e6b21010d6f777049d676382c upstream.

This removes the redundant 'write' and 'force' parameters from
__get_user_pages_locked() 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>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 4.4:
- Drop change in get_user_pages_remote()
- Adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
mm/gup.c | 37 ++++++++++++++++++++++++++-----------
1 file changed, 26 insertions(+), 11 deletions(-)

--- a/mm/gup.c
+++ b/mm/gup.c
@@ -627,7 +627,6 @@ static __always_inline long __get_user_p
struct mm_struct *mm,
unsigned long start,
unsigned long nr_pages,
- int write, int force,
struct page **pages,
struct vm_area_struct **vmas,
int *locked, bool notify_drop,
@@ -645,10 +644,6 @@ static __always_inline long __get_user_p

if (pages)
flags |= FOLL_GET;
- if (write)
- flags |= FOLL_WRITE;
- if (force)
- flags |= FOLL_FORCE;

pages_done = 0;
lock_dropped = false;
@@ -745,8 +740,15 @@ long get_user_pages_locked(struct task_s
int write, int force, struct page **pages,
int *locked)
{
- return __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
- pages, NULL, locked, true, FOLL_TOUCH);
+ 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);
}
EXPORT_SYMBOL(get_user_pages_locked);

@@ -767,9 +769,15 @@ __always_inline long __get_user_pages_un
{
long ret;
int locked = 1;
+
+ if (write)
+ gup_flags |= FOLL_WRITE;
+ if (force)
+ gup_flags |= FOLL_FORCE;
+
down_read(&mm->mmap_sem);
- ret = __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
- pages, NULL, &locked, false, gup_flags);
+ ret = __get_user_pages_locked(tsk, mm, start, nr_pages, pages, NULL,
+ &locked, false, gup_flags);
if (locked)
up_read(&mm->mmap_sem);
return ret;
@@ -861,8 +869,15 @@ long get_user_pages(struct task_struct *
unsigned long start, unsigned long nr_pages, int write,
int force, struct page **pages, struct vm_area_struct **vmas)
{
- return __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
- pages, vmas, NULL, false, FOLL_TOUCH);
+ 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, vmas, NULL, false, flags);
}
EXPORT_SYMBOL(get_user_pages);