linux-kernel - [PATCH v3 2/2][v4.9.y] coredump: fix race condition between mmget_not_zero()/get_task

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Message-ID: <1561208539-29682-2-git-send-email-akaher@vmware.com>
Date:   Sat, 22 Jun 2019 18:32:18 +0530
From:   Ajay Kaher <akaher@...are.com>
To:     <aarcange@...hat.com>, <jannh@...gle.com>, <oleg@...hat.com>,
        <peterx@...hat.com>, <rppt@...ux.ibm.com>, <jgg@...lanox.com>,
        <mhocko@...e.com>
CC:     <jglisse@...hat.com>, <akpm@...ux-foundation.org>,
        <mike.kravetz@...cle.com>, <viro@...iv.linux.org.uk>,
        <riandrews@...roid.com>, <arve@...roid.com>,
        <yishaih@...lanox.com>, <dledford@...hat.com>,
        <sean.hefty@...el.com>, <hal.rosenstock@...il.com>,
        <matanb@...lanox.com>, <leonro@...lanox.com>,
        <linux-fsdevel@...r.kernel.org>, <linux-mm@...ck.org>,
        <devel@...verdev.osuosl.org>, <linux-rdma@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>,
        <akaher@...are.com>, <srivatsab@...are.com>, <amakhalov@...are.com>
Subject: [PATCH v3 2/2][v4.9.y] coredump: fix race condition between mmget_not_zero()/get_task_mm() 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 <akaher@...are.com>
---
 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);
-- 
2.7.4