linux-kernel - [PATCH 3.16 244/305] s390/qeth: fix length check in SNMP processing

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Date:   Sun, 03 Feb 2019 14:45:08 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "David S. Miller" <davem@...emloft.net>,
        "Ursula Braun" <ubraun@...ux.ibm.com>,
        "Julian Wiedmann" <jwi@...ux.ibm.com>
Subject: [PATCH 3.16 244/305] s390/qeth: fix length check in SNMP processing

3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Julian Wiedmann <jwi@...ux.ibm.com>

commit 9a764c1e59684c0358e16ccaafd870629f2cfe67 upstream.

The response for a SNMP request can consist of multiple parts, which
the cmd callback stages into a kernel buffer until all parts have been
received. If the callback detects that the staging buffer provides
insufficient space, it bails out with error.
This processing is buggy for the first part of the response - while it
initially checks for a length of 'data_len', it later copies an
additional amount of 'offsetof(struct qeth_snmp_cmd, data)' bytes.

Fix the calculation of 'data_len' for the first part of the response.
This also nicely cleans up the memcpy code.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Julian Wiedmann <jwi@...ux.ibm.com>
Reviewed-by: Ursula Braun <ubraun@...ux.ibm.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/s390/net/qeth_core_main.c | 27 ++++++++++++---------------
 1 file changed, 12 insertions(+), 15 deletions(-)

--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -4414,8 +4414,8 @@ static int qeth_snmp_command_cb(struct q
 {
 	struct qeth_ipa_cmd *cmd;
 	struct qeth_arp_query_info *qinfo;
-	struct qeth_snmp_cmd *snmp;
 	unsigned char *data;
+	void *snmp_data;
 	__u16 data_len;
 
 	QETH_CARD_TEXT(card, 3, "snpcmdcb");
@@ -4423,7 +4423,6 @@ static int qeth_snmp_command_cb(struct q
 	cmd = (struct qeth_ipa_cmd *) sdata;
 	data = (unsigned char *)((char *)cmd - reply->offset);
 	qinfo = (struct qeth_arp_query_info *) reply->param;
-	snmp = &cmd->data.setadapterparms.data.snmp;
 
 	if (cmd->hdr.return_code) {
 		QETH_CARD_TEXT_(card, 4, "scer1%i", cmd->hdr.return_code);
@@ -4436,10 +4435,15 @@ static int qeth_snmp_command_cb(struct q
 		return 0;
 	}
 	data_len = *((__u16 *)QETH_IPA_PDU_LEN_PDU1(data));
-	if (cmd->data.setadapterparms.hdr.seq_no == 1)
-		data_len -= (__u16)((char *)&snmp->data - (char *)cmd);
-	else
-		data_len -= (__u16)((char *)&snmp->request - (char *)cmd);
+	if (cmd->data.setadapterparms.hdr.seq_no == 1) {
+		snmp_data = &cmd->data.setadapterparms.data.snmp;
+		data_len -= offsetof(struct qeth_ipa_cmd,
+				     data.setadapterparms.data.snmp);
+	} else {
+		snmp_data = &cmd->data.setadapterparms.data.snmp.request;
+		data_len -= offsetof(struct qeth_ipa_cmd,
+				     data.setadapterparms.data.snmp.request);
+	}
 
 	/* check if there is enough room in userspace */
 	if ((qinfo->udata_len - qinfo->udata_offset) < data_len) {
@@ -4452,16 +4456,9 @@ static int qeth_snmp_command_cb(struct q
 	QETH_CARD_TEXT_(card, 4, "sseqn%i",
 		cmd->data.setadapterparms.hdr.seq_no);
 	/*copy entries to user buffer*/
-	if (cmd->data.setadapterparms.hdr.seq_no == 1) {
-		memcpy(qinfo->udata + qinfo->udata_offset,
-		       (char *)snmp,
-		       data_len + offsetof(struct qeth_snmp_cmd, data));
-		qinfo->udata_offset += offsetof(struct qeth_snmp_cmd, data);
-	} else {
-		memcpy(qinfo->udata + qinfo->udata_offset,
-		       (char *)&snmp->request, data_len);
-	}
+	memcpy(qinfo->udata + qinfo->udata_offset, snmp_data, data_len);
 	qinfo->udata_offset += data_len;
+
 	/* check if all replies received ... */
 		QETH_CARD_TEXT_(card, 4, "srtot%i",
 			       cmd->data.setadapterparms.hdr.used_total);