[PATCH rdma-next 1/4] IB/mlx4: Take write semaphore when changing the vma struct

[Leon Romanovsky <leon-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

From: Maor Gottlieb <maorg-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>

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-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Signed-off-by: Leon Romanovsky <leon-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
---
 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 fba94df28cf1..a2c9629f63d0 100644
--- a/drivers/infiniband/hw/mlx4/main.c
+++ b/drivers/infiniband/hw/mlx4/main.c
@@ -1173,7 +1173,7 @@ 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)
@@ -1191,7 +1191,7 @@ 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);
 }
-- 
2.12.0

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