From: Dan Williams <dan.j.williams@intel.com>
To: Hugh Dickins <hughd@google.com>
Cc: "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
Linux MM <linux-mm@kvack.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"stable@vger.kernel.org" <stable@vger.kernel.org>,
Pawel Lebioda <pawel.lebioda@intel.com>
Subject: Re: [PATCH] device-dax: fail all private mapping attempts
Date: Tue, 6 Dec 2016 17:11:50 -0800 [thread overview]
Message-ID: <CAPcyv4hp03_K1vMsf-=bxuKRYzX=ZMX+bcwnGwLbaoST_JwWjA@mail.gmail.com> (raw)
In-Reply-To: <alpine.LSU.2.11.1612051648270.1536@eggly.anvils>
On Mon, Dec 5, 2016 at 5:01 PM, Hugh Dickins <hughd@google.com> wrote:
> On Wed, 16 Nov 2016, Dan Williams wrote:
>
>> The device-dax implementation originally tried to be tricky and allow
>> private read-only mappings, but in the process allowed writable
>> MAP_PRIVATE + MAP_NORESERVE mappings. For simplicity and predictability
>> just fail all private mapping attempts since device-dax memory is
>> statically allocated and will never support overcommit.
>>
>> Cc: <stable@vger.kernel.org>
>> Cc: Dave Hansen <dave.hansen@linux.intel.com>
>> Fixes: dee410792419 ("/dev/dax, core: file operations and dax-mmap")
>> Reported-by: Pawel Lebioda <pawel.lebioda@intel.com>
>> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
>> ---
>> drivers/dax/dax.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/dax/dax.c b/drivers/dax/dax.c
>> index 0e499bfca41c..3d94ff20fdca 100644
>> --- a/drivers/dax/dax.c
>> +++ b/drivers/dax/dax.c
>> @@ -270,8 +270,8 @@ static int check_vma(struct dax_dev *dax_dev, struct vm_area_struct *vma,
>> if (!dax_dev->alive)
>> return -ENXIO;
>>
>> - /* prevent private / writable mappings from being established */
>> - if ((vma->vm_flags & (VM_NORESERVE|VM_SHARED|VM_WRITE)) == VM_WRITE) {
>> + /* prevent private mappings from being established */
>> + if ((vma->vm_flags & VM_SHARED) != VM_SHARED) {
>
> I think that is more restrictive than you intended: haven't tried,
> but I believe it rejects a PROT_READ, MAP_SHARED, O_RDONLY fd mmap,
> leaving no way to mmap /dev/dax without write permission to it.
>
> See line 1393 of mm/mmap.c: the test you want is probably
> if (!(vma->vm_flags & VM_MAYSHARE))
>
Yes, it is. Thank you!
Fix for the fix on the way...
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prev parent reply other threads:[~2016-12-07 1:11 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-16 17:26 Dan Williams
2016-12-06 1:01 ` Hugh Dickins
2016-12-07 1:11 ` Dan Williams [this message]
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