CVE-2022-49767

Estado: AnalizadaMedia (5.5)—

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().

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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]

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Puntuación base: 5.5

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.20%
Percentil entre todas las CVEs puntuadas: 9
Fecha de la puntuación: 5/10/2026

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

NVD-CWE-noinfo

Referencias

JSON original (NVD)

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      "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't 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's suggestion]"
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      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: 9p/trans_fd: syzbot reporta que la tarea se bloquea en p9_fd_close() [1], ya que p9_mux_poll_stop() de p9_conn_destroy() de p9_fd_close() no interrumpe las solicitudes kernel_read() de p9_fd_read() de p9_read_work() o kernel_write() de p9_fd_write() de p9_write_work() ya iniciadas. Dado que p9_socket_open() establece el indicador O_NONBLOCK, p9_mux_poll_stop() no necesita interrumpir kernel_read()/kernel_write(). Sin embargo, dado que p9_fd_open() no establece el indicador O_NONBLOCK, sino que bloquea la tubería a menos que la señal esté pendiente, p9_mux_poll_stop() necesita interrumpir kernel_read()/kernel_write() cuando el descriptor de archivo hace referencia a una tubería. En otras palabras, el descriptor de archivo de la tubería debe manejarse como si fuera un descriptor de archivo de socket. De alguna manera, necesitamos interrumpir kernel_read()/kernel_write() en las tuberías. Un cambio mínimo, que este parche está realizando, es establecer el indicador O_NONBLOCK de p9_fd_open(), ya que el indicador O_NONBLOCK no afecta la lectura/escritura de archivos normales. Pero este enfoque cambia el indicador O_NONBLOCK en los descriptores de archivo proporcionados por el espacio de usuario (lo que podría romper los programas del espacio de usuario), y el indicador O_NONBLOCK podría ser cambiado por el espacio de usuario. Sería posible establecer el indicador O_NONBLOCK cada vez que se invoca p9_fd_read()/p9_fd_write(), pero aún queda una pequeña ventana de tiempo para borrar el indicador O_NONBLOCK. Si no queremos manipular el indicador O_NONBLOCK, podríamos rodear kernel_read()/kernel_write() con set_thread_flag(TIF_SIGPENDING) y recalc_sigpending(). Dado que los trabajos de p9_read_work()/p9_write_work() son procesados por hilos del núcleo que procesan la cola de trabajo global system_wq, no se pudieron enviar señales desde hilos remotos al llamar a p9_mux_poll_stop() de p9_conn_destroy() de p9_fd_close(). Por lo tanto, sería necesario llamar a set_thread_flag(TIF_SIGPENDING)/recalc_sigpending() cada vez si dependemos de señales para que kernel_read()/kernel_write() sea no bloqueante. [Dominique: añadir comentario a la sugerencia de Christian]"
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  "lastModified": "2026-06-17T05:19:05.850",
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