[PATCH 01/10] mm: remove write/force parameters from __get_user_pages_locked()

Lorenzo Stoakes
2016-10-13T00:20:11Z

This patch removes the 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>
---
mm/gup.c | 47 +++++++++++++++++++++++++++++++++--------------
1 file changed, 33 insertions(+), 14 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 96b2b2f..ba83942 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -729,7 +729,6 @@ static __always_inline 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,
struct vm_area_struct **vmas,
int *locked, bool notify_drop,
@@ -747,10 +746,6 @@ static __always_inline long __get_user_pages_locked(struct task_struct *tsk,

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

pages_done = 0;
lock_dropped = false;
@@ -846,9 +841,15 @@ long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
int write, int force, 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(current, current->mm, start, nr_pages,
- write, force, pages, NULL, locked, true,
- FOLL_TOUCH);
+ pages, NULL, locked, true, flags);
}
EXPORT_SYMBOL(get_user_pages_locked);

@@ -869,9 +870,15 @@ __always_inline long __get_user_pages_unlocked(struct task_struct *tsk, struct m
{
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;
@@ -963,9 +970,15 @@ long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
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 | FOLL_REMOTE);
+ unsigned int flags = FOLL_TOUCH | FOLL_REMOTE;
+
+ 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_remote);

@@ -979,9 +992,15 @@ long get_user_pages(unsigned long start, unsigned long nr_pages,
int write, int force, struct page **pages,
struct vm_area_struct **vmas)
{
+ unsigned int flags = FOLL_TOUCH;
+
+ if (write)
+ flags |= FOLL_WRITE;
+ if (force)
+ flags |= FOLL_FORCE;
+
return __get_user_pages_locked(current, current->mm, start, nr_pages,
- write, force, pages, vmas, NULL, false,
- FOLL_TOUCH);
+ pages, vmas, NULL, false, flags);
}
EXPORT_SYMBOL(get_user_pages);

--
2.10.0