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: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.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:
 - 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: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index d4e8077..391ae8a 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -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);

diff --git a/mm/gup.c b/mm/gup.c
index bed758f..9aee694 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -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);
 

diff --git a/mm/nommu.c b/mm/nommu.c
index 92be862..5462ed8 100644 (file)
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -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);
 

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b814ae6..e4be695 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -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;