infiniband: fix race condition between infiniband mlx4, mlx5 driver and core dumping [Linux 4.9.188]

This Linux kernel change "infiniband: fix race condition between infiniband mlx4, mlx5 driver and core dumping" is included in the Linux 4.9.188 release. This change is authored by Ajay Kaher <akaher [at] vmware.com> on Sun Aug 4 09:29:26 2019 +0530. The commit for this change in Linux stable tree is 91c3a6c (patch).

infiniband: fix race condition between infiniband mlx4, mlx5 driver and core dumping

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 <[email protected]>
Reviewed-by: Jason Gunthorpe <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

There are 7 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/infiniband/hw/mlx4/main.c | 4 +++-
 drivers/infiniband/hw/mlx5/main.c | 3 +++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/hw/mlx4/main.c b/drivers/infiniband/hw/mlx4/main.c
index 8d59a59..7ccf722 100644
--- a/drivers/infiniband/hw/mlx4/main.c
+++ b/drivers/infiniband/hw/mlx4/main.c
@@ -1172,6 +1172,8 @@ static void mlx4_ib_disassociate_ucontext(struct ib_ucontext *ibcontext)
     * 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)
@@ -1190,7 +1192,7 @@ static void mlx4_ib_disassociate_ucontext(struct ib_ucontext *ibcontext)
        /* 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);
diff --git a/drivers/infiniband/hw/mlx5/main.c b/drivers/infiniband/hw/mlx5/main.c
index b1daf5c..f94df0e 100644
--- a/drivers/infiniband/hw/mlx5/main.c
+++ b/drivers/infiniband/hw/mlx5/main.c
@@ -1307,6 +1307,8 @@ static void mlx5_ib_disassociate_ucontext(struct ib_ucontext *ibcontext)
     * mlx5_ib_vma_close.
     */
    down_write(&owning_mm->mmap_sem);
+   if (!mmget_still_valid(owning_mm))
+       goto skip_mm;
    list_for_each_entry_safe(vma_private, n, &context->vma_private_list,
                 list) {
        vma = vma_private->vma;
@@ -1321,6 +1323,7 @@ static void mlx5_ib_disassociate_ucontext(struct ib_ucontext *ibcontext)
        list_del(&vma_private->list);
        kfree(vma_private);
    }
+skip_mm:
    up_write(&owning_mm->mmap_sem);
    mmput(owning_mm);
    put_task_struct(owning_process);

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