[PATCH 4.14 44/45] infiniband: fix race condition between infiniband mlx4, mlx5 driver and core dumping

[Greg Kroah-Hartman]

From: Ajay Kaher <aka...@vmware.com>

This patch is the extension of following upstream commit to fix
the race condition between get_task_mm() and core dumping
for IB->mlx4 and IB->mlx5 drivers:

commit 04f5866e41fb ("coredump: fix race condition between
mmget_not_zero()/get_task_mm() and core dumping")'

Thanks to Jason for pointing this.

Signed-off-by: Ajay Kaher <aka...@vmware.com>
Acked-by: Jason Gunthorpe <j...@mellanox.com>
---
 drivers/infiniband/hw/mlx4/main.c |    4 +++-
 drivers/infiniband/hw/mlx5/main.c |    3 +++
 2 files changed, 6 insertions(+), 1 deletion(-)

--- a/drivers/infiniband/hw/mlx4/main.c
+++ b/drivers/infiniband/hw/mlx4/main.c
@@ -1197,6 +1197,8 @@ static void mlx4_ib_disassociate_ucontex
         * mlx4_ib_vma_close().
         */
        down_write(&owning_mm->mmap_sem);
+       if (!mmget_still_valid(owning_mm))
+               goto skip_mm;
        for (i = 0; i < HW_BAR_COUNT; i++) {
                vma = context->hw_bar_info[i].vma;
                if (!vma)
@@ -1215,7 +1217,7 @@ static void mlx4_ib_disassociate_ucontex
                /* context going to be destroyed, should not access ops any 
more */
                context->hw_bar_info[i].vma->vm_ops = NULL;
        }
-
+skip_mm:
        up_write(&owning_mm->mmap_sem);
        mmput(owning_mm);
        put_task_struct(owning_process);
--- a/drivers/infiniband/hw/mlx5/main.c
+++ b/drivers/infiniband/hw/mlx5/main.c
@@ -1646,6 +1646,8 @@ static void mlx5_ib_disassociate_ucontex
         * mlx5_ib_vma_close.
         */
        down_write(&owning_mm->mmap_sem);
+       if (!mmget_still_valid(owning_mm))
+               goto skip_mm;
        mutex_lock(&context->vma_private_list_mutex);
        list_for_each_entry_safe(vma_private, n, &context->vma_private_list,
                                 list) {
@@ -1662,6 +1664,7 @@ static void mlx5_ib_disassociate_ucontex
                kfree(vma_private);
        }
        mutex_unlock(&context->vma_private_list_mutex);
+skip_mm:
        up_write(&owning_mm->mmap_sem);
        mmput(owning_mm);
        put_task_struct(owning_process);