Re: [PATCH 3.8 08/13] mnt: Only change user settable mount flags in remount

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On 2014/10/14 12:30, Eric W. Biederman wrote:
> Zefan Li <lizefan@xxxxxxxxxx> writes:
> 
>> On 2014/9/30 15:53, Francis Moreau wrote:
>>> Hello Zefan Li,
>>>
>>> I'm really not sure but this patch might be needed for 3.4 too.
>>>
>>
>> It looks to me this bug fix is for user namespace only and IIRC userns was
>> introduced in 3.8, so I'm not going to apply it to 3.4.
>>
>> Same for the other patch.
> 
> I don't know about the other patch, and the security issue is with
> respect to user namespaces and unprivileged mounts.  The bug where
> remount can clear internal mount flags is present in 3.4.  remount has
> been broken in this way for a long time.
> 
> I don't recall which mount flags you the incomplete MNT_PROPOGATION_MASK
> but I seem to remember that if you were clever and stood on your head
> and squinted you there was at least one flag that could be cleared by
> root by accident.
> 

Thanks for the information. I'll queue it for 3.4.

The other patch is "mnt: Correct permission checks in do_remount".
http://patchwork.ozlabs.org/patch/382813/

I think that's really for 3.8+.

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