ghsa-wc2r-g885-938p
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
usb: xhci: Don't skip on Stopped - Length Invalid
Up until commit d56b0b2ab142 ("usb: xhci: ensure skipped isoc TDs are returned when isoc ring is stopped") in v6.11, the driver didn't skip missed isochronous TDs when handling Stoppend and Stopped - Length Invalid events. Instead, it erroneously cleared the skip flag, which would cause the ring to get stuck, as future events won't match the missed TD which is never removed from the queue until it's cancelled.
This buggy logic seems to have been in place substantially unchanged since the 3.x series over 10 years ago, which probably speaks first and foremost about relative rarity of this case in normal usage, but by the spec I see no reason why it shouldn't be possible.
After d56b0b2ab142, TDs are immediately skipped when handling those Stopped events. This poses a potential problem in case of Stopped - Length Invalid, which occurs either on completed TDs (likely already given back) or Link and No-Op TRBs. Such event won't be recognized as matching any TD (unless it's the rare Link TRB inside a TD) and will result in skipping all pending TDs, giving them back possibly before they are done, risking isoc data loss and maybe UAF by HW.
As a compromise, don't skip and don't clear the skip flag on this kind of event. Then the next event will skip missed TDs. A downside of not handling Stopped - Length Invalid on a Link inside a TD is that if the TD is cancelled, its actual length will not be updated to account for TRBs (silently) completed before the TD was stopped.
I had no luck producing this sequence of completion events so there is no compelling demonstration of any resulting disaster. It may be a very rare, obscure condition. The sole motivation for this patch is that if such unlikely event does occur, I'd rather risk reporting a cancelled partially done isoc frame as empty than gamble with UAF.
This will be fixed more properly by looking at Stopped event's TRB pointer when making skipping decisions, but such rework is unlikely to be backported to v6.12, which will stay around for a few years.
{
"affected": [],
"aliases": [
"CVE-2025-22023"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-04-16T11:15:42Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nusb: xhci: Don\u0027t skip on Stopped - Length Invalid\n\nUp until commit d56b0b2ab142 (\"usb: xhci: ensure skipped isoc TDs are\nreturned when isoc ring is stopped\") in v6.11, the driver didn\u0027t skip\nmissed isochronous TDs when handling Stoppend and Stopped - Length\nInvalid events. Instead, it erroneously cleared the skip flag, which\nwould cause the ring to get stuck, as future events won\u0027t match the\nmissed TD which is never removed from the queue until it\u0027s cancelled.\n\nThis buggy logic seems to have been in place substantially unchanged\nsince the 3.x series over 10 years ago, which probably speaks first\nand foremost about relative rarity of this case in normal usage, but\nby the spec I see no reason why it shouldn\u0027t be possible.\n\nAfter d56b0b2ab142, TDs are immediately skipped when handling those\nStopped events. This poses a potential problem in case of Stopped -\nLength Invalid, which occurs either on completed TDs (likely already\ngiven back) or Link and No-Op TRBs. Such event won\u0027t be recognized\nas matching any TD (unless it\u0027s the rare Link TRB inside a TD) and\nwill result in skipping all pending TDs, giving them back possibly\nbefore they are done, risking isoc data loss and maybe UAF by HW.\n\nAs a compromise, don\u0027t skip and don\u0027t clear the skip flag on this\nkind of event. Then the next event will skip missed TDs. A downside\nof not handling Stopped - Length Invalid on a Link inside a TD is\nthat if the TD is cancelled, its actual length will not be updated\nto account for TRBs (silently) completed before the TD was stopped.\n\nI had no luck producing this sequence of completion events so there\nis no compelling demonstration of any resulting disaster. It may be\na very rare, obscure condition. The sole motivation for this patch\nis that if such unlikely event does occur, I\u0027d rather risk reporting\na cancelled partially done isoc frame as empty than gamble with UAF.\n\nThis will be fixed more properly by looking at Stopped event\u0027s TRB\npointer when making skipping decisions, but such rework is unlikely\nto be backported to v6.12, which will stay around for a few years.",
"id": "GHSA-wc2r-g885-938p",
"modified": "2025-04-16T12:31:19Z",
"published": "2025-04-16T12:31:19Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-22023"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/49cf6f5293aeb706dd672608478336a003f37df6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/58d0a3fab5f4fdc112c16a4c6d382f62097afd1c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6af20ac254cbd0e1178a3542767c9308e209eee5"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/de9e78167f760a699806793d7c987239e4f6c8c3"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date |
|---|
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