From: Christoph Hellwig <hch@lst.de>
To: Ralph Campbell <rcampbell@nvidia.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
nouveau@lists.freedesktop.org,
"Jérôme Glisse" <jglisse@redhat.com>,
"Jason Gunthorpe" <jgg@mellanox.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Christoph Hellwig" <hch@lst.de>
Subject: Re: [PATCH 2/2] mm/hmm: hmm_range_fault() infinite loop
Date: Sun, 25 Aug 2019 00:39:07 +0200 [thread overview]
Message-ID: <20190824223907.GB21891@lst.de> (raw)
In-Reply-To: <20190823221753.2514-3-rcampbell@nvidia.com>
On Fri, Aug 23, 2019 at 03:17:53PM -0700, Ralph Campbell wrote:
> Normally, callers to handle_mm_fault() are supposed to check the
> vma->vm_flags first. hmm_range_fault() checks for VM_READ but doesn't
> check for VM_WRITE if the caller requests a page to be faulted in
> with write permission (via the hmm_range.pfns[] value).
> If the vma is write protected, this can result in an infinite loop:
> hmm_range_fault()
> walk_page_range()
> ...
> hmm_vma_walk_hole()
> hmm_vma_walk_hole_()
> hmm_vma_do_fault()
> handle_mm_fault(FAULT_FLAG_WRITE)
> /* returns VM_FAULT_WRITE */
> /* returns -EBUSY */
> /* returns -EBUSY */
> /* returns -EBUSY */
> /* loops on -EBUSY and range->valid */
> Prevent this by checking for vma->vm_flags & VM_WRITE before calling
> handle_mm_fault().
>
> Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Looks good,
Reviewed-by: Christoph Hellwig <hch@lst.de>
next prev parent reply other threads:[~2019-08-24 22:39 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-23 22:17 [PATCH 0/2] mm/hmm: two bug fixes for hmm_range_fault() Ralph Campbell
2019-08-23 22:17 ` Ralph Campbell
2019-08-23 22:17 ` [PATCH 1/2] mm/hmm: hmm_range_fault() NULL pointer bug Ralph Campbell
2019-08-23 22:17 ` Ralph Campbell
2019-08-24 22:37 ` Christoph Hellwig
2019-08-24 22:37 ` Christoph Hellwig
2019-08-26 18:02 ` Ralph Campbell
2019-08-26 18:02 ` Ralph Campbell
2019-08-26 18:09 ` Jason Gunthorpe
2019-08-26 18:21 ` Ralph Campbell
2019-08-23 22:17 ` [PATCH 2/2] mm/hmm: hmm_range_fault() infinite loop Ralph Campbell
2019-08-23 22:17 ` Ralph Campbell
2019-08-24 22:39 ` Christoph Hellwig [this message]
2019-08-27 18:41 ` Jason Gunthorpe
2019-08-27 20:16 ` Ralph Campbell
2019-08-27 20:16 ` Ralph Campbell
2019-08-27 22:22 ` Jason Gunthorpe
2019-08-27 22:48 ` [PATCH 0/2] mm/hmm: two bug fixes for hmm_range_fault() Jason Gunthorpe
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