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

    thanks,

    greg k-h

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