From: Hillf Danton <hdanton@sina.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: Kevin Tian <kevin.tian@intel.com>,
Yan Zhao <yan.y.zhao@intel.com>,
linux-kernel@vger.kernel.org, Hillf Danton <hdanton@sina.com>,
iommu@lists.linux-foundation.org,
Markus Elfring <Markus.Elfring@web.de>,
Christoph Hellwig <hch@lst.de>
Subject: [RFC PATCH] vfio: type1: fix kthread use case
Date: Mon, 6 Jul 2020 18:49:15 +0800 [thread overview]
Message-ID: <20200706104915.11460-1-hdanton@sina.com> (raw)
It's incorrect to tell out if a task is kthread without checking
PF_KTHREAD at all.
What's also fixed, if no need to be in a seperate patch, is to
invoke kthread_use_mm() without checking the current mm first as
the kthread may hold a mm struct atm and it's not the right place
to switch mm.
Fixes: 8d46c0cca5f4 ("vfio: introduce vfio_dma_rw to read/write a range of IOVAs")
Cc: Yan Zhao <yan.y.zhao@intel.com>
Cc: Markus Elfring <Markus.Elfring@web.de>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hillf Danton <hdanton@sina.com>
---
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -2798,7 +2798,8 @@ static int vfio_iommu_type1_dma_rw_chunk
struct mm_struct *mm;
unsigned long vaddr;
struct vfio_dma *dma;
- bool kthread = current->mm == NULL;
+ bool kthread = current->flags & PF_KTHREAD;
+ bool use_mm = current->mm == NULL;
size_t offset;
*copied = 0;
@@ -2812,11 +2813,10 @@ static int vfio_iommu_type1_dma_rw_chunk
return -EPERM;
mm = get_task_mm(dma->task);
-
if (!mm)
return -EPERM;
- if (kthread)
+ if (kthread && use_mm)
kthread_use_mm(mm);
else if (current->mm != mm)
goto out;
@@ -2843,7 +2843,7 @@ static int vfio_iommu_type1_dma_rw_chunk
} else
*copied = copy_from_user(data, (void __user *)vaddr,
count) ? 0 : count;
- if (kthread)
+ if (kthread && use_mm)
kthread_unuse_mm(mm);
out:
mmput(mm);
--
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next reply other threads:[~2020-07-06 10:59 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-06 10:49 Hillf Danton [this message]
2020-07-06 11:32 ` [RFC PATCH] vfio: type1: fix kthread use case Markus Elfring
2020-07-06 12:42 ` Hillf Danton
2020-07-06 13:33 ` Markus Elfring
2020-07-06 14:08 ` Hillf Danton
2020-07-06 14:04 ` Markus Elfring
2020-07-07 1:14 ` Hillf Danton
2020-07-07 6:04 ` Markus Elfring
2020-07-07 0:31 ` Yan Zhao
2020-07-07 2:00 ` Hillf Danton
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