Re: [PATCH 07/10] mm: replace get_user_pages_remote() write/force parameters with gup_flags

On Thu 13-10-16 01:20:17, Lorenzo Stoakes wrote:

This patch removes the write and force parameters from get_user_pages_remote() and replaces them with a gup_flags parameter 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

Looks good. You can add:

Reviewed-by: Jan Kara jack@suse.cz

Honza

---

drivers/gpu/drm/etnaviv/etnaviv_gem.c | 7 +++++-- drivers/gpu/drm/i915/i915_gem_userptr.c | 6 +++++- drivers/infiniband/core/umem_odp.c | 7 +++++-- fs/exec.c | 9 +++++++-- include/linux/mm.h | 2 +- kernel/events/uprobes.c | 6 ++++-- mm/gup.c | 22 +++++++--------------- mm/memory.c | 6 +++++- security/tomoyo/domain.c | 2 +- 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 5ce3603..0370b84 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 e537930..c6f780f 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 75077a0..1f0fe32 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 6fcfb3f..4e497b9 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 686a477..2a481d3 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 d4129bb..f9ec9ad 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 dc91303..0deecf3 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -905,9 +905,7 @@ 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.

  • Should be at least nr_pages long. Or NULL, if caller
    

  • only intends to ensure the pages are faulted in.
    

@@ -936,9 +934,9 @@ EXPORT_SYMBOL(get_user_pages_unlocked);

• or similar operation cannot guarantee anything stronger anyway because
• locks can't be held over the syscall boundary.

• • If write=0, the page must not be written to. If the page is written to,
• • set_page_dirty (or set_page_dirty_lock, as appropriate) must be called
• • after the page is finished with, and before put_page is called.

• • If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page
• • is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must
• • be called after the page is finished with, and before put_page is called.
  • get_user_pages is typically used for fewer-copy IO operations, to get a
  • handle on the memory by some means other than accesses via the user virtual

@@ -955,18 +953,12 @@ EXPORT_SYMBOL(get_user_pages_unlocked); */ 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)

{

• 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);
  

• 		       NULL, false,
  

• 		       gup_flags | FOLL_TOUCH | FOLL_REMOTE);
  

} EXPORT_SYMBOL(get_user_pages_remote);

diff --git a/mm/memory.c b/mm/memory.c index fc1987d..20a9adb 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3873,6 +3873,10 @@ static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm, { struct vm_area_struct *vma; void *old_buf = buf;

• unsigned int flags = FOLL_FORCE;

• if (write)

• flags |= FOLL_WRITE;
  
  

  down_read(&mm->mmap_sem); /* ignore errors, just check how much was successfully transferred */

@@ -3882,7 +3886,7 @@ static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm, struct page *page = NULL;

ret = get_user_pages_remote(tsk, mm, addr, 1,

• 		write, 1, &page, &vma);
  

• 		flags, &page, &vma);
  

  if (ret <= 0) {

#ifndef CONFIG_HAVE_IOREMAP_PROT break; diff --git a/security/tomoyo/domain.c b/security/tomoyo/domain.c index ade7c6c..682b73a 100644 --- a/security/tomoyo/domain.c +++ b/security/tomoyo/domain.c @@ -881,7 +881,7 @@ bool tomoyo_dump_page(struct linux_binprm *bprm, unsigned long pos, * the execve(). */ if (get_user_pages_remote(current, bprm->mm, pos, 1,

• 		0, 1, &page, NULL) <= 0)
  

• 		FOLL_FORCE, &page, NULL) <= 0)
  

  return false;

#else page = bprm->page[pos / PAGE_SIZE]; -- 2.10.0