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

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

[Leon Romanovsky]

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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[PATCH rdma-next 2/4] IB/mlx4: Change vma from shared to private

[Leon Romanovsky]

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

Anonymous VMA (->vm_ops == NULL) cannot be shared, otherwise
it would lead to SIGBUS.

Remove the shared flags from the vma after we change it to be
anonymous.

This is easily reproduced by doing modprobe -r while running a
user-space application such as raw_ethernet_bw.

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 | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/infiniband/hw/mlx4/main.c b/drivers/infiniband/hw/mlx4/main.c
index a2c9629f63d0..e6efc7c34c9a 100644
--- a/drivers/infiniband/hw/mlx4/main.c
+++ b/drivers/infiniband/hw/mlx4/main.c
@@ -1187,6 +1187,8 @@ static void mlx4_ib_disassociate_ucontext(struct ib_ucontext *ibcontext)
 			BUG_ON(1);
 		}
 
+		context->hw_bar_info[i].vma->vm_flags &=
+			~(VM_SHARED | VM_MAYSHARE);
 		/* context going to be destroyed, should not access ops any more */
 		context->hw_bar_info[i].vma->vm_ops = NULL;
 	}
-- 
2.12.0

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[PATCH rdma-next 3/4] IB/mlx5: Take write semaphore when changing the vma struct

[Leon Romanovsky]

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: 7c2344c3bbf97 ('IB/mlx5: Implements disassociate_ucontext API')
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/mlx5/main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/hw/mlx5/main.c b/drivers/infiniband/hw/mlx5/main.c
index 4dc0a8785fe0..88070a7cde48 100644
--- a/drivers/infiniband/hw/mlx5/main.c
+++ b/drivers/infiniband/hw/mlx5/main.c
@@ -1478,7 +1478,7 @@ static void mlx5_ib_disassociate_ucontext(struct ib_ucontext *ibcontext)
 	/* 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;
@@ -1492,7 +1492,7 @@ static void mlx5_ib_disassociate_ucontext(struct ib_ucontext *ibcontext)
 		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);
 }
-- 
2.12.0

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[PATCH rdma-next 4/4] IB/mlx5: Change vma from shared to private

[Leon Romanovsky]

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

Anonymous VMA (->vm_ops == NULL) cannot be shared, otherwise
it would lead to SIGBUS.

Remove the shared flags from the vma after we change it to be
anonymous.

This is easily reproduced by doing modprobe -r while running a
user-space application such as raw_ethernet_bw.

Fixes: 7c2344c3bbf97 ('IB/mlx5: Implements disassociate_ucontext API')
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/mlx5/main.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/infiniband/hw/mlx5/main.c b/drivers/infiniband/hw/mlx5/main.c
index 88070a7cde48..3ecb3c3f6ed2 100644
--- a/drivers/infiniband/hw/mlx5/main.c
+++ b/drivers/infiniband/hw/mlx5/main.c
@@ -1488,6 +1488,7 @@ static void mlx5_ib_disassociate_ucontext(struct ib_ucontext *ibcontext)
 		/* context going to be destroyed, should
 		 * not access ops any more.
 		 */
+		vma->vm_flags &= ~(VM_SHARED | VM_MAYSHARE);
 		vma->vm_ops = NULL;
 		list_del(&vma_private->list);
 		kfree(vma_private);
-- 
2.12.0

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

[Doug Ledford]

On Wed, 2017-03-29 at 06:03 +0300, Leon Romanovsky wrote:
> 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>

Thanks, series applied.

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