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

From: Steve French <smfrench@gmail.com>
To: "Srivatsa S. Bhat" <srivatsa@csail.mit.edu>
Cc: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Thomas Backlund" <tmb@mageia.org>,
	"Aurélien Aptel" <aaptel@suse.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Stable <stable@vger.kernel.org>,
	"Ronnie Sahlberg" <lsahlber@redhat.com>,
	"Pavel Shilovskiy" <pshilov@microsoft.com>,
	CIFS <linux-cifs@vger.kernel.org>
Subject: Re: [PATCH 4.13 28/43] SMB3: Validate negotiate request must always be signed
Date: Tue, 27 Feb 2018 11:55:44 -0600	[thread overview]
Message-ID: <CAH2r5mvhpuE_Y=J0zyarCEvgxuOUoyO5i=nkJap7deuLT_F=jQ@mail.gmail.com> (raw)
In-Reply-To: <6bca5a97-f581-86b8-12ad-77147619d519@csail.mit.edu>

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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.

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

On Tue, Feb 27, 2018 at 11:45 AM, Srivatsa S. Bhat <srivatsa@csail.mit.edu>
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@gmail.com>
> >>>>>>>>
> >>>>>>>> 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@gmail.com>
> >>>>>>>> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> >>>>>>>>
> >>>>>>>> ---
> >>>>>>>>   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
>

-- 
Thanks,

Steve

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