net: usb: rtl8150: fix use-after-free in rtl8150_start_xmit()_CVE-2026-52982

9.8 / 10

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Description

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.

AI Analysis

AI processing failed - invalid JSON response

Basic Information

ID CVE-2026-52982

Source Linux

Published Jun 24, 2026 at 16:28

Modified Jun 28, 2026 at 06:37

Affected Product

Vendor Linux

Product Linux

Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2

Affected Versions Linux Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Linux Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Linux Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Linux Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Linux Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Linux Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Linux Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Linux Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
Linux Linux 2.6.12

References

{
    "lastseen": "",
    "description": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: usb: rtl8150: fix use-after-free in rtl8150_start_xmit()\n\nsyzbot reported a KASAN slab-use-after-free read in rtl8150_start_xmit()\nwhen accessing skb->len for tx statistics after usb_submit_urb() has\nbeen called:\n\n  BUG: KASAN: slab-use-after-free in rtl8150_start_xmit+0x71f/0x760\n    drivers/net/usb/rtl8150.c:712\n  Read of size 4 at addr ffff88810eb7a930 by task kworker/0:4/5226\n\nThe URB completion handler write_bulk_callback() frees the skb via\ndev_kfree_skb_irq(dev->tx_skb). The URB may complete on another CPU\nin softirq context before usb_submit_urb() returns in the submitter,\nso by the time the submitter reads skb->len the skb has already been\nqueued to the per-CPU completion_queue and freed by net_tx_action():\n\n  CPU A (xmit)                      CPU B (USB completion softirq)\n  ------------                      ------------------------------\n  dev->tx_skb = skb;\n  usb_submit_urb()      --+\n                          |-------> write_bulk_callback()\n                          |           dev_kfree_skb_irq(dev->tx_skb)\n                          |         net_tx_action()\n                          |           napi_skb_cache_put()   <-- free\n  netdev->stats.tx_bytes  |\n    += skb->len;          <-- UAF read\n\nFix it by caching skb->len before submitting the URB and using the\ncached value when updating the tx_bytes counter.\n\nThe pre-existing tx_bytes semantics are preserved: the counter tracks\nthe original frame length (skb->len), not the ETH_ZLEN/USB-alignment\npadded \"count\" value that is handed to the device.  Changing that\nwould be a user-visible accounting change and is out of scope for\nthis UAF fix.",
    "published": "2026-06-24T16:28:57.763Z",
    "modified": "2026-06-28T06:37:35.269Z",
    "type": "cve",
    "title": "net: usb: rtl8150: fix use-after-free in rtl8150_start_xmit()",
    "source": "Linux",
    "references": "https://git.kernel.org/stable/c/5af290c86fa81ddbc86a08d54229af5daa40c6a4\nhttps://git.kernel.org/stable/c/24831b0b2ada9fef18d1f486b7b7c444ee5ba637\nhttps://git.kernel.org/stable/c/423b5b86e14e190f6e3161eb5f2ea5f908295ba7\nhttps://git.kernel.org/stable/c/5db090ca07b28a63fb1499690cf19a3f3adafacb\nhttps://git.kernel.org/stable/c/30cf9829d09ca958279c937af8e35495cd2f1e09\nhttps://git.kernel.org/stable/c/6999d70e0eda39af029fa1891c48f0a8832b09d5\nhttps://git.kernel.org/stable/c/4dd7eb94f79486b77ca6b4c8676aedbc465dc802\nhttps://git.kernel.org/stable/c/23f0e34c64acba15cad4d23e50f41f533da195fa",
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