# CVE-2022-49767: linux: In the Linux kernel, the following vulnerability has been resolved:  9p/trans_fd: always use O_NONBLOCK read/write  s...

CVE-2022-49767 is fixed in linux on 1 platform, first by DEBIAN-CVE-2022-49767, released May 1, 2025. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2022-49767
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0020
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 1, 2025

## Description

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]

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.0.10-1 | [DEBIAN-CVE-2022-49767](https://patchblox.com/security/data/fix/linux/debian-cve-2022-49767.md) | May 1, 2025 |
| Linux | linux Debian 13.5 (trixie) | 6.0.10-1 | [DEBIAN-CVE-2022-49767](https://patchblox.com/security/data/fix/linux/debian-cve-2022-49767.md) | May 1, 2025 |
| Linux | linux Debian 14 | 6.0.10-1 | [DEBIAN-CVE-2022-49767](https://patchblox.com/security/data/fix/linux/debian-cve-2022-49767.md) | May 1, 2025 |

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