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

This removes the 'write' and 'force' from get_user_pages_remote() 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>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

9 files changed, 40 insertions, 27 deletions

diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
index 5ce3603e6eac..0370b842d9cc 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
@@ -748,19 +748,22 @@ static struct page **etnaviv_gem_userptr_do_get_pages(
         int ret = 0, pinned, npages = etnaviv_obj->base.size >> PAGE_SHIFT;
         struct page **pvec;
         uintptr_t ptr;
+        unsigned int flags = 0;
 
         pvec = drm_malloc_ab(npages, sizeof(struct page *));
         if (!pvec)
                 return ERR_PTR(-ENOMEM);
 
+        if (!etnaviv_obj->userptr.ro)
+                flags |= FOLL_WRITE;
+
         pinned = 0;
         ptr = etnaviv_obj->userptr.ptr;
 
         down_read(&mm->mmap_sem);
         while (pinned < npages) {
                 ret = get_user_pages_remote(task, mm, ptr, npages - pinned,
-                                            !etnaviv_obj->userptr.ro, 0,
-                                            pvec + pinned, NULL);
+                                            flags, pvec + pinned, NULL);
                 if (ret < 0)
                         break;
 
diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c
index e537930c64b5..c6f780f5abc9 100644
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -508,6 +508,10 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work)
         pvec = drm_malloc_gfp(npages, sizeof(struct page *), GFP_TEMPORARY);
         if (pvec != NULL) {
                 struct mm_struct *mm = obj->userptr.mm->mm;
+                unsigned int flags = 0;
+
+                if (!obj->userptr.read_only)
+                        flags |= FOLL_WRITE;
 
                 ret = -EFAULT;
                 if (atomic_inc_not_zero(&mm->mm_users)) {
@@ -517,7 +521,7 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work)
                                         (work->task, mm,
                                          obj->userptr.ptr + pinned * PAGE_SIZE,
                                          npages - pinned,
-                                         !obj->userptr.read_only, 0,
+                                         flags,
                                          pvec + pinned, NULL);
                                 if (ret < 0)
                                         break;
diff --git a/drivers/infiniband/core/umem_odp.c b/drivers/infiniband/core/umem_odp.c
index 75077a018675..1f0fe3217f23 100644
--- a/drivers/infiniband/core/umem_odp.c
+++ b/drivers/infiniband/core/umem_odp.c
@@ -527,6 +527,7 @@ int ib_umem_odp_map_dma_pages(struct ib_umem *umem, u64 user_virt, u64 bcnt,
         u64 off;
         int j, k, ret = 0, start_idx, npages = 0;
         u64 base_virt_addr;
+        unsigned int flags = 0;
 
         if (access_mask == 0)
                 return -EINVAL;
@@ -556,6 +557,9 @@ int ib_umem_odp_map_dma_pages(struct ib_umem *umem, u64 user_virt, u64 bcnt,
                 goto out_put_task;
         }
 
+        if (access_mask & ODP_WRITE_ALLOWED_BIT)
+                flags |= FOLL_WRITE;
+
         start_idx = (user_virt - ib_umem_start(umem)) >> PAGE_SHIFT;
         k = start_idx;
 
@@ -574,8 +578,7 @@ int ib_umem_odp_map_dma_pages(struct ib_umem *umem, u64 user_virt, u64 bcnt,
                  */
                 npages = get_user_pages_remote(owning_process, owning_mm,
                                 user_virt, gup_num_pages,
-                                access_mask & ODP_WRITE_ALLOWED_BIT,
-                                0, local_page_list, NULL);
+                                flags, local_page_list, NULL);
                 up_read(&owning_mm->mmap_sem);
 
                 if (npages < 0)
diff --git a/fs/exec.c b/fs/exec.c
index 6fcfb3f7b137..4e497b9ee71e 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -191,6 +191,7 @@ static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 {
         struct page *page;
         int ret;
+        unsigned int gup_flags = FOLL_FORCE;
 
 #ifdef CONFIG_STACK_GROWSUP
         if (write) {
@@ -199,12 +200,16 @@ static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
                         return NULL;
         }
 #endif
+
+        if (write)
+                gup_flags |= FOLL_WRITE;
+
         /*
          * We are doing an exec().  'current' is the process
          * doing the exec and bprm->mm is the new process's mm.
          */
-        ret = get_user_pages_remote(current, bprm->mm, pos, 1, write,
-                        1, &page, NULL);
+        ret = get_user_pages_remote(current, bprm->mm, pos, 1, gup_flags,
+                        &page, NULL);
         if (ret <= 0)
                 return NULL;
 
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 30bb5d9631bb..ecc4be7b67e0 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1276,7 +1276,7 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                       struct vm_area_struct **vmas, int *nonblocking);
 long get_user_pages_remote(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,
                             struct vm_area_struct **vmas);
 long get_user_pages(unsigned long start, unsigned long nr_pages,
                             unsigned int gup_flags, struct page **pages,
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index d4129bb05e5d..f9ec9add2164 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -300,7 +300,8 @@ int uprobe_write_opcode(struct mm_struct *mm, unsigned long vaddr,
 
 retry:
         /* Read the page with vaddr into memory */
-        ret = get_user_pages_remote(NULL, mm, vaddr, 1, 0, 1, &old_page, &vma);
+        ret = get_user_pages_remote(NULL, mm, vaddr, 1, FOLL_FORCE, &old_page,
+                        &vma);
         if (ret <= 0)
                 return ret;
 
@@ -1710,7 +1711,8 @@ static int is_trap_at_addr(struct mm_struct *mm, unsigned long vaddr)
          * but we treat this as a 'remote' access since it is
          * essentially a kernel access to the memory.
          */
-        result = get_user_pages_remote(NULL, mm, vaddr, 1, 0, 1, &page, NULL);
+        result = get_user_pages_remote(NULL, mm, vaddr, 1, FOLL_FORCE, &page,
+                        NULL);
         if (result < 0)
                 return result;
 
diff --git a/mm/gup.c b/mm/gup.c
index bbc2e76cdd77..7aa113c2d373 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -915,9 +915,7 @@ EXPORT_SYMBOL(get_user_pages_unlocked);
  * @mm:         mm_struct of target mm
  * @start:      starting user address
  * @nr_pages:   number of pages from start to pin
- * @write:      whether pages will be written to by the caller
- * @force:      whether to force access even when user mapping is currently
- *              protected (but never forces write access to shared mapping).
+ * @gup_flags:  flags modifying lookup behaviour
  * @pages:      array that receives pointers to the pages pinned.