Description (CNA)
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]
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 27979bb2ff748613dba96ae66392a76fb0678527 before 0b5e6bd72b8171364616841603a70e4ba9837063; affected 27979bb2ff748613dba96ae66392a76fb0678527 before 9f8554615df668e4bf83294633ee9d232b28ce45; affected 27979bb2ff748613dba96ae66392a76fb0678527 before 7abf40f06a76c0dff42eada10597917e9776fbd4; affected 27979bb2ff748613dba96ae66392a76fb0678527 before b1ad04da7fe4515e2ce2d5f2dcab3b5b6d45614b; affected 27979bb2ff748613dba96ae66392a76fb0678527 before a8e2fc8f7b41fa9d9ca5f624f4e4d34fce5b40a9; affected 27979bb2ff748613dba96ae66392a76fb0678527 before 0e07032b4b4724b8ad1003698cb81083c1818999; affected 27979bb2ff748613dba96ae66392a76fb0678527 before 5af16182c5639349415118e9e9aecd8355f7a08b; affected 27979bb2ff748613dba96ae66392a76fb0678527 before ef575281b21e9a34dfae544a187c6aac2ae424a9 |
| Linux / Linux | affected 2.6.17; unaffected 0 before 2.6.17; unaffected 4.9.334 through 4.9.*; unaffected 4.14.300 through 4.14.*; unaffected 4.19.267 through 4.19.*; unaffected 5.4.225 through 5.4.*; unaffected 5.10.156 through 5.10.*; unaffected 5.15.80 through 5.15.*; unaffected 6.0.10 through 6.0.*; unaffected 6.1 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/0b5e6bd72b8171364616841603a70e4ba9837063
- https://git.kernel.org/stable/c/9f8554615df668e4bf83294633ee9d232b28ce45
- https://git.kernel.org/stable/c/7abf40f06a76c0dff42eada10597917e9776fbd4
- https://git.kernel.org/stable/c/b1ad04da7fe4515e2ce2d5f2dcab3b5b6d45614b
- https://git.kernel.org/stable/c/a8e2fc8f7b41fa9d9ca5f624f4e4d34fce5b40a9
- https://git.kernel.org/stable/c/0e07032b4b4724b8ad1003698cb81083c1818999
- https://git.kernel.org/stable/c/5af16182c5639349415118e9e9aecd8355f7a08b
- https://git.kernel.org/stable/c/ef575281b21e9a34dfae544a187c6aac2ae424a9