IB/mlx4: Take write semaphore when changing the vma struct

[ Upstream commit 22c3653d04bd0c67b75e99d85e0c0bdf83947df5 ]

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: ae184ddeca5db ('IB/mlx4_ib: Disassociate support')
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/infiniband/hw/mlx4/main.c b/drivers/infiniband/hw/mlx4/main.c
index c41c8d0..129dbd7 100644 (file)
--- a/drivers/infiniband/hw/mlx4/main.c
+++ b/drivers/infiniband/hw/mlx4/main.c
@@ -1168,7 +1168,7 @@ static void mlx4_ib_disassociate_ucontext(struct ib_ucontext *ibcontext)
        /* need to protect from a race on closing the vma as part of
         * mlx4_ib_vma_close().
         */
-       down_read(&owning_mm->mmap_sem);
+       down_write(&owning_mm->mmap_sem);
        for (i = 0; i < HW_BAR_COUNT; i++) {
                vma = context->hw_bar_info[i].vma;
                if (!vma)
@@ -1186,7 +1186,7 @@ static void mlx4_ib_disassociate_ucontext(struct ib_ucontext *ibcontext)
                context->hw_bar_info[i].vma->vm_ops = NULL;
        }
 
-       up_read(&owning_mm->mmap_sem);
+       up_write(&owning_mm->mmap_sem);
        mmput(owning_mm);
        put_task_struct(owning_process);
 }