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From: Ralph Boehme <slow@samba.org>
To: Namjae Jeon <linkinjeon@kernel.org>, linux-cifs@vger.kernel.org
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>,
	Steve French <smfrench@gmail.com>
Subject: Re: [PATCH v2 2/3] ksmbd: add validation in smb2 negotiate
Date: Wed, 22 Sep 2021 16:17:40 +0200	[thread overview]
Message-ID: <433e36b5-f07c-0105-fd30-c7bb4cb8957d@samba.org> (raw)
In-Reply-To: <20210921225109.6388-2-linkinjeon@kernel.org>


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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.

>   	__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?

> +			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


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  reply	other threads:[~2021-09-22 14:17 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 [this message]
2021-09-22 23:13     ` Namjae Jeon
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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