6.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: Daniel Starke daniel.starke@siemens.com
commit 3a75b205de43365f80a33b98ec9289785da56243 upstream.
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.
Fixes: c568f7086c6e ("tty: n_gsm: fix missing timer to handle stalled links") Cc: stable stable@kernel.org Signed-off-by: Daniel Starke daniel.starke@siemens.com Link: https://lore.kernel.org/r/20231026055844.3127-1-daniel.starke@siemens.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/n_gsm.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -4058,6 +4058,8 @@ static int gsm_modem_upd_via_msc(struct
static int gsm_modem_update(struct gsm_dlci *dlci, u8 brk) { + if (dlci->gsm->dead) + return -EL2HLT; if (dlci->adaption == 2) { /* Send convergence layer type 2 empty data frame. */ gsm_modem_upd_via_data(dlci, brk);