mm: replace get_user_pages_unlocked() write/force parameters with gup_flags

commit c164154f66f0c9b02673f07aa4f044f1d9c70274 upstream.

This removes the 'write' and 'force' use from get_user_pages_unlocked()
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>
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:
 - Also update calls from process_vm_rw_single_vec() and async_pf_execute()
 - Adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 12 insertions, 21 deletions

diff --git a/mm/gup.c b/mm/gup.c
index 9aee6945f349..6bbec1b694ea 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -797,17 +797,10 @@ EXPORT_SYMBOL(__get_user_pages_unlocked);
  */
 long get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
 			     unsigned long start, unsigned long nr_pages,
-			     int write, int force, struct page **pages)
+			     struct page **pages, unsigned int gup_flags)
 {
-	unsigned int flags = FOLL_TOUCH;
-
-	if (write)
-		flags |= FOLL_WRITE;
-	if (force)
-		flags |= FOLL_FORCE;
-
 	return __get_user_pages_unlocked(tsk, mm, start, nr_pages,
-					 pages, flags);
+					 pages, gup_flags | FOLL_TOUCH);
 }
 EXPORT_SYMBOL(get_user_pages_unlocked);
 
@@ -1427,7 +1420,8 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write,
 		pages += nr;
 
 		ret = get_user_pages_unlocked(current, mm, start,
-					      nr_pages - nr, write, 0, pages);
+					      nr_pages - nr, pages,
+					      write ? FOLL_WRITE : 0);
 
 		/* Have to be a bit careful with return values */
 		if (nr > 0) {
diff --git a/mm/nommu.c b/mm/nommu.c
index f5322195dbcd..e249e06579fb 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -224,17 +224,10 @@ EXPORT_SYMBOL(__get_user_pages_unlocked);
 
 long get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
 			     unsigned long start, unsigned long nr_pages,
-			     int write, int force, struct page **pages)
+			     struct page **pages, unsigned int gup_flags)
 {
-	unsigned int flags = 0;
-
-	if (write)
-		flags |= FOLL_WRITE;
-	if (force)
-		flags |= FOLL_FORCE;
-
 	return __get_user_pages_unlocked(tsk, mm, start, nr_pages,
-					 pages, flags);
+					 pages, gup_flags);
 }
 EXPORT_SYMBOL(get_user_pages_unlocked);
 
diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
index 5d453e58ddbf..1b5a6104c5fc 100644
--- a/mm/process_vm_access.c
+++ b/mm/process_vm_access.c
@@ -88,19 +88,23 @@ static int process_vm_rw_single_vec(unsigned long addr,
 	ssize_t rc = 0;
 	unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
 		/ sizeof(struct pages *);
+	unsigned int flags = 0;
 
 	/* Work out address and page range required */
 	if (len == 0)
 		return 0;
 	nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1;
 
+	if (vm_write)
+		flags |= FOLL_WRITE;
+
 	while (!rc && nr_pages && iov_iter_count(iter)) {
 		int pages = min(nr_pages, max_pages_per_loop);
 		size_t bytes;
 
 		/* Get the pages we're interested in */
 		pages = get_user_pages_unlocked(task, mm, pa, pages,
-						vm_write, 0, process_pages);
+						process_pages, flags);
 		if (pages <= 0)
 			return -EFAULT;
 
diff --git a/mm/util.c b/mm/util.c
index 5fae5b9c2885..db39235970c6 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -278,7 +278,7 @@ int __weak get_user_pages_fast(unsigned long start,
 {
 	struct mm_struct *mm = current->mm;
 	return get_user_pages_unlocked(current, mm, start, nr_pages,
-				       write, 0, pages);
+				       pages, write ? FOLL_WRITE : 0);
 }
 EXPORT_SYMBOL_GPL(get_user_pages_fast);