linux-kernel - [PATCH] iommu/amd: Take mmap_sem when calling get_user

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Message-ID: <1398724066-3730-1-git-send-email-suravee.suthikulpanit@amd.com>
Date:	Mon, 28 Apr 2014 17:27:46 -0500
From:	<suravee.suthikulpanit@....com>
To:	<iommu@...ts.linux-foundation.org>, <joro@...tes.org>
CC:	<linux-kernel@...r.kernel.org>, <kim.naru@....com>,
	<jay.cornwall@....com>,
	Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PATCH] iommu/amd: Take mmap_sem when calling get_user_pages

From: Jay Cornwall <jay.cornwall@....com>

get_user_pages requires caller to hold a read lock on mmap_sem.

Signed-off-by: Jay Cornwall <jay.cornwall@....com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 drivers/iommu/amd_iommu_v2.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iommu/amd_iommu_v2.c b/drivers/iommu/amd_iommu_v2.c
index 5208828..203b2e6 100644
--- a/drivers/iommu/amd_iommu_v2.c
+++ b/drivers/iommu/amd_iommu_v2.c
@@ -504,8 +504,10 @@ static void do_fault(struct work_struct *work)
 
 	write = !!(fault->flags & PPR_FAULT_WRITE);
 
+	down_read(&fault->state->mm->mmap_sem);
 	npages = get_user_pages(fault->state->task, fault->state->mm,
 				fault->address, 1, write, 0, &page, NULL);
+	up_read(&fault->state->mm->mmap_sem);
 
 	if (npages == 1) {
 		put_page(page);
-- 
1.7.10.4

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