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Commit ab424c8e authored by Lorenzo Stoakes's avatar Lorenzo Stoakes Committed by Greg Kroah-Hartman
Browse files

mm: remove write/force parameters from __get_user_pages_unlocked() 



commit d4944b0ecec0af882483fe44b66729316e575208 upstream.

This removes the redundant 'write' and 'force' parameters from
__get_user_pages_unlocked() 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: default avatarLorenzo Stoakes <lstoakes@gmail.com>
Acked-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 4.4:
 - Defer changes in process_vm_rw_single_vec() and async_pf_execute() since
   they use get_user_pages_unlocked() here
 - Adjust context]
Signed-off-by: default avatarBen Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 6a3c9524

include/linux/mm.h

+1 −2
Original line number Diff line number Diff line
@@ -1207,8 +1207,7 @@ long get_user_pages_locked(struct task_struct *tsk, struct mm_struct *mm, 
		    int *locked);

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,

			       unsigned int gup_flags);

			       struct page **pages, unsigned int gup_flags);

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);

mm/gup.c

+10 −9
Original line number Diff line number Diff line
@@ -764,17 +764,11 @@ EXPORT_SYMBOL(get_user_pages_locked); 
 */

__always_inline 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,

					       unsigned int gup_flags)

					       struct page **pages, unsigned int gup_flags)

{

	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, pages, NULL,

				      &locked, false, gup_flags);
@@ -805,8 +799,15 @@ 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)

{

	return __get_user_pages_unlocked(tsk, mm, start, nr_pages, write,

					 force, pages, FOLL_TOUCH);

	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);

}

EXPORT_SYMBOL(get_user_pages_unlocked);

mm/nommu.c

+10 −4
Original line number Diff line number Diff line
@@ -211,8 +211,7 @@ EXPORT_SYMBOL(get_user_pages_locked); 


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,

			       unsigned int gup_flags)

			       struct page **pages, unsigned int gup_flags)

{

	long ret;

	down_read(&mm->mmap_sem);
@@ -227,8 +226,15 @@ 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)

{

	return __get_user_pages_unlocked(tsk, mm, start, nr_pages, write,

					 force, pages, 0);

	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);

}

EXPORT_SYMBOL(get_user_pages_unlocked);

virt/kvm/kvm_main.c

+8 −3
Original line number Diff line number Diff line
@@ -1352,10 +1352,15 @@ static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault, 
		npages = get_user_page_nowait(current, current->mm,

					      addr, write_fault, page);

		up_read(&current->mm->mmap_sem);

	} else

	} else {

		unsigned int flags = FOLL_TOUCH | FOLL_HWPOISON;



		if (write_fault)

			flags |= FOLL_WRITE;



		npages = __get_user_pages_unlocked(current, current->mm, addr, 1,

						   write_fault, 0, page,

						   FOLL_TOUCH|FOLL_HWPOISON);

						   page, flags);

	}

	if (npages != 1)

		return npages;