CVE ID:	CVE-2023-52872
Description:	In the Linux kernel, the following vulnerability has been resolved: tty: n_gsm: fix race condition in status line change on dead connections gsm_cleanup_mux() cleans up the gsm by closing all DLCIs, stopping all timers, removing the virtual tty devices and clearing the data queues. This procedure, however, may cause subsequent changes of the virtual modem status lines of a DLCI. More data is being added the outgoing data queue and the deleted kick timer is restarted to handle this. At this point many resources have already been removed by the cleanup procedure. Thus, a kernel panic occurs. Fix this by proving in gsm_modem_update() that the cleanup procedure has not been started and the mux is still alive. Note that writing to a virtual tty is already protected by checks against the DLCI specific connection state.
Test IDs:	None available
Cross References:	Common Vulnerability Exposure (CVE) ID: CVE-2023-52872 https://git.kernel.org/stable/c/19d34b73234af542cc8a218cf398dee73cdb1890 https://git.kernel.org/stable/c/19d34b73234af542cc8a218cf398dee73cdb1890 https://git.kernel.org/stable/c/3a75b205de43365f80a33b98ec9289785da56243 https://git.kernel.org/stable/c/3a75b205de43365f80a33b98ec9289785da56243 https://git.kernel.org/stable/c/81a4dd5e6c78f5d8952fa8c9d36565db1fe01444 https://git.kernel.org/stable/c/81a4dd5e6c78f5d8952fa8c9d36565db1fe01444 https://git.kernel.org/stable/c/ce4df90333c4fe65acb8b5089fdfe9b955ce976a https://git.kernel.org/stable/c/ce4df90333c4fe65acb8b5089fdfe9b955ce976a https://git.kernel.org/stable/c/df6cfab66ff2a44bd23ad5dd5309cb3421bb6593 https://git.kernel.org/stable/c/df6cfab66ff2a44bd23ad5dd5309cb3421bb6593