Re: [PATCH 4.13 28/43] SMB3: Validate negotiate request must always be signed

[Srivatsa S. Bhat]

On 2/27/18 9:56 AM, Steve French wrote:
> This shouldn't be too hard to figure out if willing to backport a
> slightly larger set of fixes to the older stable, but I don't have a
> system running 4.9 stable.
> 

If you have the proposed patches that apply on 4.9, I'd be happy to
try them out!

[ I would have offered to backport the patches myself, but actually I
already tried doing that with a larger set of patches from mainline
(picking those commits between the regression and the fix that seemed
relevant), but I felt quite out-of-depth trying to adapt them to 4.9
and 4.4, as I'm not that familiar with the internals of SMB/CIFS. ]

> Is this the correct stable tree branch?
> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/log/?h=linux-4.9.y
> 

Yep!

Regards,
Srivatsa

> On Tue, Feb 27, 2018 at 11:45 AM, Srivatsa S. Bhat
> <srivatsa@xxxxxxxxxxxxx> wrote:
>> On 2/27/18 4:40 AM, Greg Kroah-Hartman wrote:
>>> On Tue, Feb 27, 2018 at 01:22:31AM -0800, Srivatsa S. Bhat wrote:
>>>> On 2/27/18 12:54 AM, Greg Kroah-Hartman wrote:
>>>>> On Mon, Feb 26, 2018 at 07:44:28PM -0800, Srivatsa S. Bhat wrote:
>>>>>> On 1/3/18 6:15 PM, Srivatsa S. Bhat wrote:
>>>>>>> On 11/1/17 8:18 AM, Greg Kroah-Hartman wrote:
>>>>>>>> On Tue, Oct 31, 2017 at 03:02:11PM +0200, Thomas Backlund wrote:
>>>>>>>>> Den 31.10.2017 kl. 11:55, skrev Greg Kroah-Hartman:
>>>>>>>>>> 4.13-stable review patch.  If anyone has any objections, please let me know.
>>>>>>>>>>
>>>>>>>>>> ------------------
>>>>>>>>>>
>>>>>>>>>> From: Steve French <smfrench@xxxxxxxxx>
>>>>>>>>>>
>>>>>>>>>> commit 4587eee04e2ac7ac3ac9fa2bc164fb6e548f99cd upstream.
>>>>>>>>>>
>>>>>>>>>> According to MS-SMB2 3.2.55 validate_negotiate request must
>>>>>>>>>> always be signed. Some Windows can fail the request if you send it unsigned
>>>>>>>>>>
>>>>>>>>>> See kernel bugzilla bug 197311
>>>>>>>>>>
>>>>>>>>>> Acked-by: Ronnie Sahlberg <lsahlber.redhat.com>
>>>>>>>>>> Signed-off-by: Steve French <smfrench@xxxxxxxxx>
>>>>>>>>>> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>>>>>>>>>>
>>>>>>>>>> ---
>>>>>>>>>>   fs/cifs/smb2pdu.c |    3 +++
>>>>>>>>>>   1 file changed, 3 insertions(+)
>>>>>>>>>>
>>>>>>>>>> --- a/fs/cifs/smb2pdu.c
>>>>>>>>>> +++ b/fs/cifs/smb2pdu.c
>>>>>>>>>> @@ -1963,6 +1963,9 @@ SMB2_ioctl(const unsigned int xid, struc
>>>>>>>>>>        } else
>>>>>>>>>>                iov[0].iov_len = get_rfc1002_length(req) + 4;
>>>>>>>>>> +      /* validate negotiate request must be signed - see MS-SMB2 3.2.5.5 */
>>>>>>>>>> +      if (opcode == FSCTL_VALIDATE_NEGOTIATE_INFO)
>>>>>>>>>> +              req->hdr.sync_hdr.Flags |= SMB2_FLAGS_SIGNED;
>>>>>>>>>>        rc = SendReceive2(xid, ses, iov, n_iov, &resp_buftype, flags, &rsp_iov);
>>>>>>>>>>        cifs_small_buf_release(req);
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> This one needs to be backported to all stable kernels as the commit that
>>>>>>>>> introduced the regression:
>>>>>>>>> '
>>>>>>>>> 0603c96f3af50e2f9299fa410c224ab1d465e0f9
>>>>>>>>> SMB: Validate negotiate (to protect against downgrade) even if signing off
>>>>>>>>>
>>>>>>>>> is backported in stable trees as of: 4.9.53, 4.4.90, 3.18.73
>>>>>>>>
>>>>>>>> Oh wait, it breaks the builds on older kernels, that's why I didn't
>>>>>>>> apply it :)
>>>>>>>>
>>>>>>>> Can you provide me with a working backport?
>>>>>>>>
>>>>>>>
>>>>>>> Hi Steve,
>>>>>>>
>>>>>>> Is there a version of this fix available for stable kernels?
>>>>>>>
>>>>>>
>>>>>> Hi Greg,
>>>>>>
>>>>>> Mounting SMB3 shares continues to fail for me on 4.4.118 and 4.9.84
>>>>>> due to the issues that I have described in detail on this mail thread.
>>>>>>
>>>>>> Since there is no apparent fix for this bug on stable kernels, could
>>>>>> you please consider reverting the original commit that caused this
>>>>>> regression?
>>>>>>
>>>>>> That commit was intended to enhance security, which is probably why it
>>>>>> was backported to stable kernels in the first place; but instead it
>>>>>> ends up breaking basic functionality itself (mounting). So in the
>>>>>> absence of a proper fix, I don't see much of an option but to revert
>>>>>> that commit.
>>>>>>
>>>>>> So, please consider reverting the following:
>>>>>>
>>>>>> commit 02ef29f9cbb616bf419 "SMB: Validate negotiate (to protect
>>>>>> against downgrade) even if signing off" on 4.4.118
>>>>>>
>>>>>> commit 0e1b85a41a25ac888fb "SMB: Validate negotiate (to protect
>>>>>> against downgrade) even if signing off" on 4.9.84
>>>>>>
>>>>>> They correspond to commit 0603c96f3af50e2f9299fa410c224ab1d465e0f9
>>>>>> upstream. Both these patches should revert cleanly.
>>>>>
>>>>> Do you still have this same problem on 4.14 and 4.15?  If so, the issue
>>>>> needs to get fixed there, not papered-over by reverting these old
>>>>> changes, as you will hit the issue again in the future when you update
>>>>> to a newer kernel version.
>>>>>
>>>>
>>>> 4.14 and 4.15 work great! (I had mentioned this is in my original bug
>>>> report but forgot to summarize it here, sorry).
>>>
>>>
>>> Then what is the bugfix that should be applied here in order to keep
>>> things working with these patches applied?
>>>
>>
>> That would be the one mentioned in the subject line of this thread :)
>> However, a working backport of that fix is not available for 4.4 and
>> 4.9, hence the trouble.
>>
>> It looks like we are reconstructing elements of this email thread all
>> over again, so let me quickly summarize the status so far:
>>
>> In 4.14/4.15/mainline,
>> - commit 0603c96f3af50e2f9 (SMB: Validate negotiate (to protect against
>>   downgrade) even if signing off) caused mount regression with SMB v3.
>>
>> - commit 4587eee04e2ac7ac3 (SMB3: Validate negotiate request must
>>   always be signed) fixed the issue.
>>
>> - [ There was a lot of code churn in the CIFS/SMB codebase between
>>     these two commits in mainline. ]
>>
>> In this email thread, you backported the fix to stable 4.13. Thomas
>> noticed that the problematic commit had also made it to stable series
>> such as 4.4 and 4.9, and requested a backport of the fix to those
>> trees as well. However, a straight-forward backport of the fix to 4.4
>> and 4.9 breaks the build, so no fix was available for those kernels.
>>
>> I investigated this and tried to produce a working backport of the fix
>> to 4.4 and 4.9, but didn't succeed, despite trying several variations
>> as well as suggestions from Aurelien [1][2]. So, given that there is
>> still no known fix for the mount regression on 4.4 and 4.9 stable
>> series at this point, I decided to request a revert of the problematic
>> commit that caused the regression in those kernels.
>>
>> [1]. https://lkml.org/lkml/2018/1/3/892
>> [2]. https://lkml.org/lkml/2018/1/29/1009
>>
>> Regards,
>> Srivatsa
> 
> 
>