On 20.08.19 13:05, Dan Carpenter wrote:
> [ Kees, could we make copy_from_user() just fail if size is more than
> INT_MAX? ]
>
> Hello Julian Wiedmann,
>
Heya Dan - thanks! Agreed, that looks wrong. I'll put together a fix...
> The patch d4c08afafa04: "s390/qeth: streamline SNMP cmd code" from
> Jun 27, 2019, leads to the following static checker warning:
>
> drivers/s390/net/qeth_core_main.c:4381 qeth_snmp_command()
> error: check that 'req_len' is capped
>
> drivers/s390/net/qeth_core_main.c
> 4355 static int qeth_snmp_command(struct qeth_card *card, char __user *udata)
> 4356 {
> 4357 struct qeth_snmp_ureq __user *ureq;
> 4358 struct qeth_cmd_buffer *iob;
> 4359 unsigned int req_len;
> 4360 struct qeth_arp_query_info qinfo = {0, };
> 4361 int rc = 0;
> 4362
> 4363 QETH_CARD_TEXT(card, 3, "snmpcmd");
> 4364
> 4365 if (IS_VM_NIC(card))
> 4366 return -EOPNOTSUPP;
> 4367
> 4368 if ((!qeth_adp_supported(card, IPA_SETADP_SET_SNMP_CONTROL)) &&
> 4369 IS_LAYER3(card))
> 4370 return -EOPNOTSUPP;
> 4371
> 4372 ureq = (struct qeth_snmp_ureq __user *) udata;
> 4373 if (get_user(qinfo.udata_len, &ureq->hdr.data_len) ||
> 4374 get_user(req_len, &ureq->hdr.req_len))
> 4375 return -EFAULT;
> 4376
> 4377 iob = qeth_get_adapter_cmd(card, IPA_SETADP_SET_SNMP_CONTROL, req_len);
>
> The problem is that qeth_get_adapter_cmd() doesn't guard against integer
> overflows if reg_len is >= UINT_MAX - offsetof(struct qeth_ipacmd_setadpparms,
> data)).
>
> 4378 if (!iob)
> 4379 return -ENOMEM;
> 4380
> 4381 if (copy_from_user(&__ipa_cmd(iob)->data.setadapterparms.data.snmp,
> 4382 &ureq->cmd, req_len)) {
>
> So then this copy_from_user() could overflow. The original code had a
> similar problem but it only affect 32 bit systems. I'm not sure what is
> a good upper bound for req_len.
>
> 4383 qeth_put_cmd(iob);
> 4384 return -EFAULT;
> 4385 }
> 4386
> 4387 qinfo.udata = kzalloc(qinfo.udata_len, GFP_KERNEL);
>
> regards,
> dan carpenter
>
