CVE-2026-64121

Summary

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.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/6afdb8113cb007f9332f59a9b7fd45731b8a9de5
• https://git.kernel.org/stable/c/16bd798cb6d8337d7c3eea1adc412f31b5181d5b
• https://git.kernel.org/stable/c/301a554e458e2f5ec47f2c336a7cb03b877f9fd6
• https://git.kernel.org/stable/c/f8a5a76b4a683043c6eff2a060bcaa17f9316ad5
• https://git.kernel.org/stable/c/2638e1773904d7aa8f24c6e7fda2ed7d69df6fa4
• https://git.kernel.org/stable/c/5db89c99566fc4728cc92e941d8e1975711e24b5

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