[PATCH AUTOSEL for 4.9 064/190] IB/mlx4: Take write semaphore when changing the vma struct

[Sasha Levin]

From: Maor Gottlieb <ma...@mellanox.com>

[ 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 <ma...@mellanox.com>
Signed-off-by: Leon Romanovsky <l...@kernel.org>
Signed-off-by: Doug Ledford <dledf...@redhat.com>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
---
 drivers/infiniband/hw/mlx4/main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/hw/mlx4/main.c 
b/drivers/infiniband/hw/mlx4/main.c
index c41c8d0a4ac0..129dbd790dba 100644
--- 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);
 }
-- 
2.14.1