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Subject[PATCH 4.9 049/177] IB/mlx5: Take write semaphore when changing the vma struct
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Maor Gottlieb <maorg@mellanox.com>


[ Upstream commit ecc7d83be3243835c9396a1a2fb8ce95f205207b ]

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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/infiniband/hw/mlx5/main.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/infiniband/hw/mlx5/main.c
+++ b/drivers/infiniband/hw/mlx5/main.c
@@ -1313,7 +1313,7 @@ static void mlx5_ib_disassociate_ucontex
/* 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;
@@ -1327,7 +1327,7 @@ static void mlx5_ib_disassociate_ucontex
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);
}

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