CVE-2022-49767 Affecting kernel-debug package, versions *
Threat Intelligence
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Test your applications- Snyk IDSNYK-RHEL6-KERNELDEBUG-9946993
- published2 May 2025
- disclosed1 May 2025
Introduced: 1 May 2025
NewCVE-2022-49767 (opens in a new tab)How to fix?
There is no fixed version for RHEL:6 kernel-debug.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-debug package and not the kernel-debug package as distributed by RHEL.
See How to fix? for RHEL:6 relevant fixed versions and status.
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]
References
- https://access.redhat.com/security/cve/CVE-2022-49767
- https://git.kernel.org/stable/c/0b5e6bd72b8171364616841603a70e4ba9837063
- https://git.kernel.org/stable/c/0e07032b4b4724b8ad1003698cb81083c1818999
- https://git.kernel.org/stable/c/5af16182c5639349415118e9e9aecd8355f7a08b
- https://git.kernel.org/stable/c/7abf40f06a76c0dff42eada10597917e9776fbd4
- https://git.kernel.org/stable/c/9f8554615df668e4bf83294633ee9d232b28ce45
- https://git.kernel.org/stable/c/a8e2fc8f7b41fa9d9ca5f624f4e4d34fce5b40a9
- https://git.kernel.org/stable/c/b1ad04da7fe4515e2ce2d5f2dcab3b5b6d45614b
- https://git.kernel.org/stable/c/ef575281b21e9a34dfae544a187c6aac2ae424a9