vfio/type1: Prune vfio_pin_page_external()

With vfio_lock_acct() testing the locked memory limit under mmap_sem,
it's redundant to do it here for a single page.  We can also reorder
our tests such that we can avoid testing for reserved pages if we're
not doing accounting and let vfio_lock_acct() test the process
CAP_IPC_LOCK.  Finally, this function oddly returns 1 on success.
Update to return zero on success, -errno on error.  Since the function
only pins a single page, there's no need to return the number of pages
pinned.

N.B. vfio_pin_pages_remote() can pin a large contiguous range of pages
before calling vfio_lock_acct().  If we were to similarly remove the
extra test there, a user could temporarily pin far more pages than
they're allowed.

Suggested-by: Kirti Wankhede <kwankhede@nvidia.com>
Suggested-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index a8a079ba9477190c3f389c1801e655f12906dc5e..372e4f626138cf644927f59d510e9de2e0f99059 100644 (file)
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -482,43 +482,26 @@ static long vfio_unpin_pages_remote(struct vfio_dma *dma, dma_addr_t iova,
 static int vfio_pin_page_external(struct vfio_dma *dma, unsigned long vaddr,
                                  unsigned long *pfn_base, bool do_accounting)
 {
-       unsigned long limit;
-       bool lock_cap = has_capability(dma->task, CAP_IPC_LOCK);
        struct mm_struct *mm;
        int ret;
-       bool rsvd;
 
        mm = get_task_mm(dma->task);
        if (!mm)
                return -ENODEV;
 
        ret = vaddr_get_pfn(mm, vaddr, dma->prot, pfn_base);
-       if (ret)
-               goto pin_page_exit;
-
-       rsvd = is_invalid_reserved_pfn(*pfn_base);
-       limit = task_rlimit(dma->task, RLIMIT_MEMLOCK) >> PAGE_SHIFT;
-
-       if (!rsvd && !lock_cap && mm->locked_vm + 1 > limit) {
-               put_pfn(*pfn_base, dma->prot);
-               pr_warn("%s: Task %s (%d) RLIMIT_MEMLOCK (%ld) exceeded\n",
-                       __func__, dma->task->comm, task_pid_nr(dma->task),
-                       limit << PAGE_SHIFT);
-               ret = -ENOMEM;
-               goto pin_page_exit;
-       }
-
-       if (!rsvd && do_accounting) {
-               ret = vfio_lock_acct(dma->task, 1, &lock_cap);
+       if (!ret && do_accounting && !is_invalid_reserved_pfn(*pfn_base)) {
+               ret = vfio_lock_acct(dma->task, 1, NULL);
                if (ret) {
                        put_pfn(*pfn_base, dma->prot);
-                       goto pin_page_exit;
+                       if (ret == -ENOMEM)
+                               pr_warn("%s: Task %s (%d) RLIMIT_MEMLOCK "
+                                       "(%ld) exceeded\n", __func__,
+                                       dma->task->comm, task_pid_nr(dma->task),
+                                       task_rlimit(dma->task, RLIMIT_MEMLOCK));
                }
        }
 
-       ret = 1;
-
-pin_page_exit:
        mmput(mm);
        return ret;
 }
@@ -598,10 +581,8 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
                remote_vaddr = dma->vaddr + iova - dma->iova;
                ret = vfio_pin_page_external(dma, remote_vaddr, &phys_pfn[i],
                                             do_accounting);
-               if (ret <= 0) {
-                       WARN_ON(!ret);
+               if (ret)
                        goto pin_unwind;
-               }
 
                ret = vfio_add_to_pfn_list(dma, iova, phys_pfn[i]);
                if (ret) {