GHSA-3WJP-7H53-CFV8
Vulnerability from github – Published: 2024-06-20 12:31 – Updated: 2025-09-17 18:31In the Linux kernel, the following vulnerability has been resolved:
USB: core: Fix hang in usb_kill_urb by adding memory barriers
The syzbot fuzzer has identified a bug in which processes hang waiting for usb_kill_urb() to return. It turns out the issue is not unlinking the URB; that works just fine. Rather, the problem arises when the wakeup notification that the URB has completed is not received.
The reason is memory-access ordering on SMP systems. In outline form, usb_kill_urb() and __usb_hcd_giveback_urb() operating concurrently on different CPUs perform the following actions:
CPU 0 CPU 1 ---------------------------- --------------------------------- usb_kill_urb(): __usb_hcd_giveback_urb(): ... ... atomic_inc(&urb->reject); atomic_dec(&urb->use_count); ... ... wait_event(usb_kill_urb_queue, atomic_read(&urb->use_count) == 0); if (atomic_read(&urb->reject)) wake_up(&usb_kill_urb_queue);
Confining your attention to urb->reject and urb->use_count, you can see that the overall pattern of accesses on CPU 0 is:
write urb->reject, then read urb->use_count;
whereas the overall pattern of accesses on CPU 1 is:
write urb->use_count, then read urb->reject.
This pattern is referred to in memory-model circles as SB (for "Store Buffering"), and it is well known that without suitable enforcement of the desired order of accesses -- in the form of memory barriers -- it is entirely possible for one or both CPUs to execute their reads ahead of their writes. The end result will be that sometimes CPU 0 sees the old un-decremented value of urb->use_count while CPU 1 sees the old un-incremented value of urb->reject. Consequently CPU 0 ends up on the wait queue and never gets woken up, leading to the observed hang in usb_kill_urb().
The same pattern of accesses occurs in usb_poison_urb() and the failure pathway of usb_hcd_submit_urb().
The problem is fixed by adding suitable memory barriers. To provide proper memory-access ordering in the SB pattern, a full barrier is required on both CPUs. The atomic_inc() and atomic_dec() accesses themselves don't provide any memory ordering, but since they are present, we can use the optimized smp_mb__after_atomic() memory barrier in the various routines to obtain the desired effect.
This patch adds the necessary memory barriers.
{
"affected": [],
"aliases": [
"CVE-2022-48760"
],
"database_specific": {
"cwe_ids": [
"CWE-667"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-06-20T12:15:14Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nUSB: core: Fix hang in usb_kill_urb by adding memory barriers\n\nThe syzbot fuzzer has identified a bug in which processes hang waiting\nfor usb_kill_urb() to return. It turns out the issue is not unlinking\nthe URB; that works just fine. Rather, the problem arises when the\nwakeup notification that the URB has completed is not received.\n\nThe reason is memory-access ordering on SMP systems. In outline form,\nusb_kill_urb() and __usb_hcd_giveback_urb() operating concurrently on\ndifferent CPUs perform the following actions:\n\nCPU 0\t\t\t\t\tCPU 1\n----------------------------\t\t---------------------------------\nusb_kill_urb():\t\t\t\t__usb_hcd_giveback_urb():\n ...\t\t\t\t\t ...\n atomic_inc(\u0026urb-\u003ereject);\t\t atomic_dec(\u0026urb-\u003euse_count);\n ...\t\t\t\t\t ...\n wait_event(usb_kill_urb_queue,\n\tatomic_read(\u0026urb-\u003euse_count) == 0);\n\t\t\t\t\t if (atomic_read(\u0026urb-\u003ereject))\n\t\t\t\t\t\twake_up(\u0026usb_kill_urb_queue);\n\nConfining your attention to urb-\u003ereject and urb-\u003euse_count, you can\nsee that the overall pattern of accesses on CPU 0 is:\n\n\twrite urb-\u003ereject, then read urb-\u003euse_count;\n\nwhereas the overall pattern of accesses on CPU 1 is:\n\n\twrite urb-\u003euse_count, then read urb-\u003ereject.\n\nThis pattern is referred to in memory-model circles as SB (for \"Store\nBuffering\"), and it is well known that without suitable enforcement of\nthe desired order of accesses -- in the form of memory barriers -- it\nis entirely possible for one or both CPUs to execute their reads ahead\nof their writes. The end result will be that sometimes CPU 0 sees the\nold un-decremented value of urb-\u003euse_count while CPU 1 sees the old\nun-incremented value of urb-\u003ereject. Consequently CPU 0 ends up on\nthe wait queue and never gets woken up, leading to the observed hang\nin usb_kill_urb().\n\nThe same pattern of accesses occurs in usb_poison_urb() and the\nfailure pathway of usb_hcd_submit_urb().\n\nThe problem is fixed by adding suitable memory barriers. To provide\nproper memory-access ordering in the SB pattern, a full barrier is\nrequired on both CPUs. The atomic_inc() and atomic_dec() accesses\nthemselves don\u0027t provide any memory ordering, but since they are\npresent, we can use the optimized smp_mb__after_atomic() memory\nbarrier in the various routines to obtain the desired effect.\n\nThis patch adds the necessary memory barriers.",
"id": "GHSA-3wjp-7h53-cfv8",
"modified": "2025-09-17T18:31:14Z",
"published": "2024-06-20T12:31:22Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-48760"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/26fbe9772b8c459687930511444ce443011f86bf"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/546ba238535d925254e0b3f12012a5c55801e2f3"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5904dfd3ddaff3bf4a41c3baf0a8e8f31ed4599b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5f138ef224dffd15d5e5c5b095859719e0038427"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9340226388c66a7e090ebb00e91ed64a753b6c26"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9c61fce322ac2ef7fecf025285353570d60e41d6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b50f5ca60475710bbc9a3af32fbfc17b1e69c2f0"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c9a18f7c5b071dce5e6939568829d40994866ab0"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e3b131e30e612ff0e32de6c1cb4f69f89db29193"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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