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From: ronnie sahlberg <ronniesahlberg@gmail.com>
To: Namjae Jeon <linkinjeon@kernel.org>
Cc: Ralph Boehme <slow@samba.org>,
	linux-cifs <linux-cifs@vger.kernel.org>,
	Steve French <smfrench@gmail.com>
Subject: Re: [PATCH v2 2/3] ksmbd: add validation in smb2 negotiate
Date: Thu, 23 Sep 2021 10:12:53 +1000	[thread overview]
Message-ID: <CAN05THQYNxfMh57R8c=f5syJ-4=LhZx81kO=jxX8x=3sm-6fwQ@mail.gmail.com> (raw)
In-Reply-To: <CAKYAXd-+jfKqonB8=At-znCUBpF-J8Z3NfK=vvUJOfcUMFemoQ@mail.gmail.com>

On Thu, Sep 23, 2021 at 9:13 AM Namjae Jeon <linkinjeon@kernel.org> wrote:
>
> 2021-09-22 23:17 GMT+09:00, Ralph Boehme <slow@samba.org>:
> > Hi Namjae
> >
> > patch looks great! Few nitpicks below.
> >
> > Am 22.09.21 um 00:51 schrieb Namjae Jeon:
> >> This patch add validation to check request buffer check in smb2
> >> negotiate.
> >>
> >> Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
> >> Cc: Ralph Böhme <slow@samba.org>
> >> Cc: Steve French <smfrench@gmail.com>
> >> Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
> >> ---
> >>   fs/ksmbd/smb2pdu.c    | 41 ++++++++++++++++++++++++++++++++++++++++-
> >>   fs/ksmbd/smb_common.c | 22 ++++++++++++++++++++--
> >>   2 files changed, 60 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
> >> index baf7ce31d557..1fe37ad4e5bc 100644
> >> --- a/fs/ksmbd/smb2pdu.c
> >> +++ b/fs/ksmbd/smb2pdu.c
> >> @@ -1071,7 +1071,7 @@ int smb2_handle_negotiate(struct ksmbd_work *work)
> >>      struct ksmbd_conn *conn = work->conn;
> >>      struct smb2_negotiate_req *req = work->request_buf;
> >>      struct smb2_negotiate_rsp *rsp = work->response_buf;
> >> -    int rc = 0;
> >> +    int rc = 0, smb2_buf_len, smb2_neg_size;
> >
> > I guess all len variables should use unsigned types to facilitate well
> > defined overflow checks.
> As Ronnie pointed out, if checking max stream size, will be no problem.
> I'll fix it though.

You should add a check to ksmbd_conn_handler_loop() that the length is
< 0x01000000 too.

> >> >>      __le32 status;
> >>
> >>      ksmbd_debug(SMB, "Received negotiate request\n");
> >> @@ -1089,6 +1089,45 @@ int smb2_handle_negotiate(struct ksmbd_work *work)
> >>              goto err_out;
> >>      }
> >>
> >> +    smb2_buf_len = get_rfc1002_len(work->request_buf);
> >> +    smb2_neg_size = offsetof(struct smb2_negotiate_req, Dialects) - 4;
> >> +    if (conn->dialect == SMB311_PROT_ID) {
> >> +            int nego_ctxt_off = le32_to_cpu(req->NegotiateContextOffset);
> >> +            int nego_ctxt_count = le16_to_cpu(req->NegotiateContextCount);
> >> +
> >> +            if (smb2_buf_len < nego_ctxt_off + nego_ctxt_count) {
> >
> > overflow check needed for 32 bit arch?
> Okay, will fix it on v3.
> Thanks!
> >
> >> +                    rsp->hdr.Status = STATUS_INVALID_PARAMETER;
> >> +                    rc = -EINVAL;
> >> +                    goto err_out;
> >> +            }
> >> +
> >> +            if (smb2_neg_size > nego_ctxt_off) {
> >> +                    rsp->hdr.Status = STATUS_INVALID_PARAMETER;
> >> +                    rc = -EINVAL;
> >> +                    goto err_out;
> >> +            }
> >> +
> >> +            if (smb2_neg_size + le16_to_cpu(req->DialectCount) * sizeof(__le16) >
> >> +                nego_ctxt_off) {
> >> +                    rsp->hdr.Status = STATUS_INVALID_PARAMETER;
> >> +                    rc = -EINVAL;
> >> +                    goto err_out;
> >> +            }
> >> +    } else {
> >> +            if (smb2_neg_size > smb2_buf_len) {
> >> +                    rsp->hdr.Status = STATUS_INVALID_PARAMETER;
> >> +                    rc = -EINVAL;
> >> +                    goto err_out;
> >> +            }
> >> +
> >> +            if (smb2_neg_size + le16_to_cpu(req->DialectCount) * sizeof(__le16) >
> >> +                smb2_buf_len) {
> >> +                    rsp->hdr.Status = STATUS_INVALID_PARAMETER;
> >> +                    rc = -EINVAL;
> >> +                    goto err_out;
> >> +            }
> >> +    }
> >> +
> >>      conn->cli_cap = le32_to_cpu(req->Capabilities);
> >>      switch (conn->dialect) {
> >>      case SMB311_PROT_ID:
> >> diff --git a/fs/ksmbd/smb_common.c b/fs/ksmbd/smb_common.c
> >> index 1da67217698d..da17b21ac685 100644
> >> --- a/fs/ksmbd/smb_common.c
> >> +++ b/fs/ksmbd/smb_common.c
> >> @@ -229,13 +229,22 @@ int ksmbd_lookup_dialect_by_id(__le16 *cli_dialects,
> >> __le16 dialects_count)
> >>
> >>   static int ksmbd_negotiate_smb_dialect(void *buf)
> >>   {
> >> -    __le32 proto;
> >> +    int smb_buf_length = get_rfc1002_len(buf);
> >
> > unsigned
> >
> > Thanks!
> > -slow
> >
> > --
> > Ralph Boehme, Samba Team                 https://samba.org/
> > SerNet Samba Team Lead      https://sernet.de/en/team-samba
> >
> >

  reply	other threads:[~2021-09-23  0:13 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-21 22:51 [PATCH v2 1/3] ksmbd: remove RFC1002 check in smb2 request Namjae Jeon
2021-09-21 22:51 ` [PATCH v2 2/3] ksmbd: add validation in smb2 negotiate Namjae Jeon
2021-09-22 14:17   ` Ralph Boehme
2021-09-22 23:13     ` Namjae Jeon
2021-09-23  0:12       ` ronnie sahlberg [this message]
2021-09-23  0:25         ` Namjae Jeon
2021-09-21 22:51 ` [PATCH v2 3/3] ksmbd: fix invalid request buffer access in compound request Namjae Jeon
2021-09-22  0:39   ` ronnie sahlberg
2021-09-22  4:35     ` Namjae Jeon
2021-09-22  4:56       ` ronnie sahlberg
2021-09-22  5:35         ` Namjae Jeon

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