CVE-2026-64121

In the Linux kernel, the following vulnerability has been resolved:

net: ifb: report ethtool stats over num_tx_queues

ifb_dev_init() allocates dp->tx_private to dev->num_tx_queues

entries via kzalloc_objs(*txp, dev->num_tx_queues). Both IFB

per-queue RX and TX stats live in those entries: ifb_xmit() updates

txp->rx_stats using the skb queue mapping, ifb_ri_tasklet() updates

txp->tx_stats, and ifb_stats64() aggregates both over

dev->num_tx_queues.

The ethtool stats callbacks instead size and walk the per-queue

stats with dev->real_num_rx_queues and dev->real_num_tx_queues. With

an asymmetric device where the RX queue count exceeds the TX queue

count, for example:

ip link add name ifb10 numtxqueues 1 numrxqueues 8 type ifb

ethtool -S ifb10

ifb_get_ethtool_stats() indexes past the tx_private allocation and

copies adjacent slab data through ETHTOOL_GSTATS.

Use dev->num_tx_queues consistently for the stats strings, the

stats count, and the stats data walks. This reports one RX stats

group and one TX stats group for each backing ifb_q_private entry,

which is the queue set IFB can actually populate.

Reproduced under UML+KASAN at v7.1-rc2:

BUG: KASAN: slab-out-of-bounds in ifb_fill_stats_data+0x3c/0xae

Read of size 8 at addr 0000000062dbd228 by task ethtool/36

ifb_fill_stats_data+0x3c/0xae

ifb_get_ethtool_stats+0xc0/0x129

__dev_ethtool+0x1ca5/0x363c

dev_ethtool+0x123/0x1b3

dev_ioctl+0x56c/0x744

sock_do_ioctl+0x15f/0x1b2

sock_ioctl+0x4d5/0x50a

sys_ioctl+0xd8b/0xde9

With the patch applied, the same UML+KASAN repro is silent and

ethtool -S ifb10 reports only the stats backed by the single

allocated tx_private entry.