CVE-2026-52982

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

net: usb: rtl8150: fix use-after-free in rtl8150_start_xmit()

syzbot reported a KASAN slab-use-after-free read in rtl8150_start_xmit()

when accessing skb->len for tx statistics after usb_submit_urb() has

been called:

BUG: KASAN: slab-use-after-free in rtl8150_start_xmit+0x71f/0x760

drivers/net/usb/rtl8150.c:712

Read of size 4 at addr ffff88810eb7a930 by task kworker/0:4/5226

The URB completion handler write_bulk_callback() frees the skb via

dev_kfree_skb_irq(dev->tx_skb). The URB may complete on another CPU

in softirq context before usb_submit_urb() returns in the submitter,

so by the time the submitter reads skb->len the skb has already been

queued to the per-CPU completion_queue and freed by net_tx_action():

CPU A (xmit) CPU B (USB completion softirq)

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

dev->tx_skb = skb;

usb_submit_urb() --+

|-------> write_bulk_callback()

| dev_kfree_skb_irq(dev->tx_skb)

| net_tx_action()

| napi_skb_cache_put() <-- free

netdev->stats.tx_bytes |

+= skb->len; <-- UAF read

Fix it by caching skb->len before submitting the URB and using the

cached value when updating the tx_bytes counter.

The pre-existing tx_bytes semantics are preserved: the counter tracks

the original frame length (skb->len), not the ETH_ZLEN/USB-alignment

padded "count" value that is handed to the device. Changing that

would be a user-visible accounting change and is out of scope for

this UAF fix.