Re: [PATCH net] s390/qeth: Check CAP_NET_ADMIN for private ioctls

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] An integer underflow in the buffer size check allows privileged users to cause a kernel heap buffer overflow.
--

--- Patch [1]: [PATCH net] s390/qeth: Check CAP_NET_ADMIN for private ioctls ---
commit 3ec90fe5fb86d5d8d0432c2487ad687ef4d3e227
Author: Aswin Karuvally <aswin@linux.ibm.com>

s390/qeth: Check CAP_NET_ADMIN for private ioctls

This commit adds a CAP_NET_ADMIN capability check to the
SIOC_QETH_ADP_SET_SNMP_CONTROL, SIOC_QETH_GET_CARD_TYPE, and
SIOC_QETH_QUERY_OAT private ioctls. This ensures that these commands cannot
be invoked by unprivileged users.

> diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c
> index 20fb0d2e02a9a..f18eed9df3c7a 100644
> --- a/drivers/s390/net/qeth_core_main.c
> +++ b/drivers/s390/net/qeth_core_main.c
> @@ -6525,6 +6525,9 @@ int qeth_siocdevprivate(struct net_device *dev, struct ifreq *rq, void __user *d
>  	struct qeth_card *card = dev->ml_priv;
>  	int rc = 0;
>  
> +	if (!capable(CAP_NET_ADMIN))
> +		return -EPERM;
> +
>  	switch (cmd) {
>  	case SIOC_QETH_ADP_SET_SNMP_CONTROL:
>  		rc = qeth_snmp_command(card, data);

[Severity: High]
This is a pre-existing issue, but does qeth_snmp_command() allow an integer
underflow that leads to a heap buffer overflow?

If a user provides a udata_len smaller than sizeof(struct qeth_snmp_ureq_hdr)
(16 bytes), the unsigned subtraction in the callback underflows:

drivers/s390/net/qeth_core_main.c:qeth_snmp_command() {
    ...
	if (get_user(qinfo.udata_len, &ureq->hdr.data_len) ||
    ...
	qinfo.udata = kzalloc(qinfo.udata_len, GFP_KERNEL);
    ...
	qinfo.udata_offset = sizeof(struct qeth_snmp_ureq_hdr);
    ...
}

drivers/s390/net/qeth_core_main.c:qeth_snmp_command_cb() {
    ...
	if ((qinfo->udata_len - qinfo->udata_offset) < data_len) {
    ...
}

The underflow would bypass the available space check, leading to an
out-of-bounds memcpy into the allocated heap buffer.

The same integer underflow pattern appears to exist in qeth_l3_arp_query_cb()
for the SIOC_QETH_ARP_QUERY_INFO ioctl.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260723140050.762991-1-aswin@linux.ibm.com?part=1