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From: Namjae Jeon <linkinjeon@kernel.org>
To: Ralph Boehme <slow@samba.org>
Cc: linux-cifs@vger.kernel.org,
	Ronnie Sahlberg <ronniesahlberg@gmail.com>,
	Steve French <smfrench@gmail.com>
Subject: Re: [PATCH v2 2/3] ksmbd: add validation in smb2 negotiate
Date: Thu, 23 Sep 2021 08:13:05 +0900	[thread overview]
Message-ID: <CAKYAXd-+jfKqonB8=At-znCUBpF-J8Z3NfK=vvUJOfcUMFemoQ@mail.gmail.com> (raw)
In-Reply-To: <433e36b5-f07c-0105-fd30-c7bb4cb8957d@samba.org>

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.
>
>>   	__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:[~2021-09-22 23:13 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 [this message]
2021-09-23  0:12       ` ronnie sahlberg
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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