CVE-2022-49767 (GCVE-0-2022-49767)

Vulnerability from cvelistv5 – Published: 2025-05-01 14:09 – Updated: 2025-12-23 13:25
VLAI?
Title
9p/trans_fd: always use O_NONBLOCK read/write
Summary
In the Linux kernel, the following vulnerability has been resolved: 9p/trans_fd: always use O_NONBLOCK read/write syzbot is reporting hung task at p9_fd_close() [1], for p9_mux_poll_stop() from p9_conn_destroy() from p9_fd_close() is failing to interrupt already started kernel_read() from p9_fd_read() from p9_read_work() and/or kernel_write() from p9_fd_write() from p9_write_work() requests. Since p9_socket_open() sets O_NONBLOCK flag, p9_mux_poll_stop() does not need to interrupt kernel_read()/kernel_write(). However, since p9_fd_open() does not set O_NONBLOCK flag, but pipe blocks unless signal is pending, p9_mux_poll_stop() needs to interrupt kernel_read()/kernel_write() when the file descriptor refers to a pipe. In other words, pipe file descriptor needs to be handled as if socket file descriptor. We somehow need to interrupt kernel_read()/kernel_write() on pipes. A minimal change, which this patch is doing, is to set O_NONBLOCK flag from p9_fd_open(), for O_NONBLOCK flag does not affect reading/writing of regular files. But this approach changes O_NONBLOCK flag on userspace- supplied file descriptors (which might break userspace programs), and O_NONBLOCK flag could be changed by userspace. It would be possible to set O_NONBLOCK flag every time p9_fd_read()/p9_fd_write() is invoked, but still remains small race window for clearing O_NONBLOCK flag. If we don't want to manipulate O_NONBLOCK flag, we might be able to surround kernel_read()/kernel_write() with set_thread_flag(TIF_SIGPENDING) and recalc_sigpending(). Since p9_read_work()/p9_write_work() works are processed by kernel threads which process global system_wq workqueue, signals could not be delivered from remote threads when p9_mux_poll_stop() from p9_conn_destroy() from p9_fd_close() is called. Therefore, calling set_thread_flag(TIF_SIGPENDING)/recalc_sigpending() every time would be needed if we count on signals for making kernel_read()/kernel_write() non-blocking. [Dominique: add comment at Christian's suggestion]
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 27979bb2ff748613dba96ae66392a76fb0678527 , < 0b5e6bd72b8171364616841603a70e4ba9837063 (git)
Affected: 27979bb2ff748613dba96ae66392a76fb0678527 , < 9f8554615df668e4bf83294633ee9d232b28ce45 (git)
Affected: 27979bb2ff748613dba96ae66392a76fb0678527 , < 7abf40f06a76c0dff42eada10597917e9776fbd4 (git)
Affected: 27979bb2ff748613dba96ae66392a76fb0678527 , < b1ad04da7fe4515e2ce2d5f2dcab3b5b6d45614b (git)
Affected: 27979bb2ff748613dba96ae66392a76fb0678527 , < a8e2fc8f7b41fa9d9ca5f624f4e4d34fce5b40a9 (git)
Affected: 27979bb2ff748613dba96ae66392a76fb0678527 , < 0e07032b4b4724b8ad1003698cb81083c1818999 (git)
Affected: 27979bb2ff748613dba96ae66392a76fb0678527 , < 5af16182c5639349415118e9e9aecd8355f7a08b (git)
Affected: 27979bb2ff748613dba96ae66392a76fb0678527 , < ef575281b21e9a34dfae544a187c6aac2ae424a9 (git)
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    Linux Linux Affected: 2.6.17
Unaffected: 0 , < 2.6.17 (semver)
Unaffected: 4.9.334 , ≤ 4.9.* (semver)
Unaffected: 4.14.300 , ≤ 4.14.* (semver)
Unaffected: 4.19.267 , ≤ 4.19.* (semver)
Unaffected: 5.4.225 , ≤ 5.4.* (semver)
Unaffected: 5.10.156 , ≤ 5.10.* (semver)
Unaffected: 5.15.80 , ≤ 5.15.* (semver)
Unaffected: 6.0.10 , ≤ 6.0.* (semver)
Unaffected: 6.1 , ≤ * (original_commit_for_fix)
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{
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\n9p/trans_fd: always use O_NONBLOCK read/write\n\nsyzbot is reporting hung task at p9_fd_close() [1], for p9_mux_poll_stop()\n from p9_conn_destroy() from p9_fd_close() is failing to interrupt already\nstarted kernel_read() from p9_fd_read() from p9_read_work() and/or\nkernel_write() from p9_fd_write() from p9_write_work() requests.\n\nSince p9_socket_open() sets O_NONBLOCK flag, p9_mux_poll_stop() does not\nneed to interrupt kernel_read()/kernel_write(). However, since p9_fd_open()\ndoes not set O_NONBLOCK flag, but pipe blocks unless signal is pending,\np9_mux_poll_stop() needs to interrupt kernel_read()/kernel_write() when\nthe file descriptor refers to a pipe. In other words, pipe file descriptor\nneeds to be handled as if socket file descriptor.\n\nWe somehow need to interrupt kernel_read()/kernel_write() on pipes.\n\nA minimal change, which this patch is doing, is to set O_NONBLOCK flag\n from p9_fd_open(), for O_NONBLOCK flag does not affect reading/writing\nof regular files. But this approach changes O_NONBLOCK flag on userspace-\nsupplied file descriptors (which might break userspace programs), and\nO_NONBLOCK flag could be changed by userspace. It would be possible to set\nO_NONBLOCK flag every time p9_fd_read()/p9_fd_write() is invoked, but still\nremains small race window for clearing O_NONBLOCK flag.\n\nIf we don\u0027t want to manipulate O_NONBLOCK flag, we might be able to\nsurround kernel_read()/kernel_write() with set_thread_flag(TIF_SIGPENDING)\nand recalc_sigpending(). Since p9_read_work()/p9_write_work() works are\nprocessed by kernel threads which process global system_wq workqueue,\nsignals could not be delivered from remote threads when p9_mux_poll_stop()\n from p9_conn_destroy() from p9_fd_close() is called. Therefore, calling\nset_thread_flag(TIF_SIGPENDING)/recalc_sigpending() every time would be\nneeded if we count on signals for making kernel_read()/kernel_write()\nnon-blocking.\n\n[Dominique: add comment at Christian\u0027s suggestion]"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-12-23T13:25:50.432Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/0b5e6bd72b8171364616841603a70e4ba9837063"
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        {
          "url": "https://git.kernel.org/stable/c/9f8554615df668e4bf83294633ee9d232b28ce45"
        },
        {
          "url": "https://git.kernel.org/stable/c/7abf40f06a76c0dff42eada10597917e9776fbd4"
        },
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        {
          "url": "https://git.kernel.org/stable/c/0e07032b4b4724b8ad1003698cb81083c1818999"
        },
        {
          "url": "https://git.kernel.org/stable/c/5af16182c5639349415118e9e9aecd8355f7a08b"
        },
        {
          "url": "https://git.kernel.org/stable/c/ef575281b21e9a34dfae544a187c6aac2ae424a9"
        }
      ],
      "title": "9p/trans_fd: always use O_NONBLOCK read/write",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2022-49767",
    "datePublished": "2025-05-01T14:09:06.183Z",
    "dateReserved": "2025-04-16T07:17:33.804Z",
    "dateUpdated": "2025-12-23T13:25:50.432Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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