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    Subject[PATCH AUTOSEL for 4.9 064/190] IB/mlx4: Take write semaphore when changing the vma struct
    Date
    From: Maor Gottlieb <maorg@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 <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>
    ---
    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
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