IB/mlx5: Take write semaphore when changing the vma struct

When the driver disassociate user context, it changes the vma to
anonymous by setting the vm_ops to null and zap the vma ptes.

In order to avoid race in the kernel, we need to take write lock
before we change the vma entries.

Fixes: 7c2344c3bbf97 ('IB/mlx5: Implements disassociate_ucontext API')
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>

diff --git a/drivers/infiniband/hw/mlx5/main.c b/drivers/infiniband/hw/mlx5/main.c
index 4dc0a8785fe0d250e1b8217c79d38915ae388ef7..88070a7cde4890cdb9e0d23893e5551196857d0a 100644 (file)
--- a/drivers/infiniband/hw/mlx5/main.c
+++ b/drivers/infiniband/hw/mlx5/main.c
@@ -1478,7 +1478,7 @@ static void mlx5_ib_disassociate_ucontext(struct ib_ucontext *ibcontext)
        /* need to protect from a race on closing the vma as part of
         * mlx5_ib_vma_close.
         */
-       down_read(&owning_mm->mmap_sem);
+       down_write(&owning_mm->mmap_sem);
        list_for_each_entry_safe(vma_private, n, &context->vma_private_list,
                                 list) {
                vma = vma_private->vma;
@@ -1492,7 +1492,7 @@ static void mlx5_ib_disassociate_ucontext(struct ib_ucontext *ibcontext)
                list_del(&vma_private->list);
                kfree(vma_private);
        }
-       up_read(&owning_mm->mmap_sem);
+       up_write(&owning_mm->mmap_sem);
        mmput(owning_mm);
        put_task_struct(owning_process);
 }