From: daniel.starke@xxxxxxxxxxx <daniel.starke@xxxxxxxxxxx> commit 687f9ad43c52501f46164758e908a5dd181a87fc upstream. The function gsm_process_modem() exists to handle modem status bits of incoming frames. This includes incoming MSC (modem status command) frames and convergence layer type 2 data frames. The function, however, was only designed to handle MSC frames as it expects the command length. Within gsm_dlci_data() it is wrongly assumed that this is the same as the data frame length. This is only true if the data frame contains only 1 byte of payload. This patch names the length parameter of gsm_process_modem() in a generic manner to reflect its association. It also corrects all calls to the function to handle the variable number of modem status octets correctly in both cases. Fixes: 7263287af93d ("tty: n_gsm: Fixed logic to decode break signal from modem status") Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Daniel Starke <daniel.starke@xxxxxxxxxxx> Link: https://lore.kernel.org/r/20220218073123.2121-6-daniel.starke@xxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/tty/n_gsm.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -1009,25 +1009,25 @@ static void gsm_control_reply(struct gsm * @tty: virtual tty bound to the DLCI * @dlci: DLCI to affect * @modem: modem bits (full EA) - * @clen: command length + * @slen: number of signal octets * * Used when a modem control message or line state inline in adaption * layer 2 is processed. Sort out the local modem state and throttles */ static void gsm_process_modem(struct tty_struct *tty, struct gsm_dlci *dlci, - u32 modem, int clen) + u32 modem, int slen) { int mlines = 0; u8 brk = 0; int fc; - /* The modem status command can either contain one octet (v.24 signals) - or two octets (v.24 signals + break signals). The length field will - either be 2 or 3 respectively. This is specified in section - 5.4.6.3.7 of the 27.010 mux spec. */ + /* The modem status command can either contain one octet (V.24 signals) + * or two octets (V.24 signals + break signals). This is specified in + * section 5.4.6.3.7 of the 07.10 mux spec. + */ - if (clen == 2) + if (slen == 1) modem = modem & 0x7f; else { brk = modem & 0x7f; @@ -1084,6 +1084,7 @@ static void gsm_control_modem(struct gsm unsigned int brk = 0; struct gsm_dlci *dlci; int len = clen; + int slen; const u8 *dp = data; struct tty_struct *tty; @@ -1103,6 +1104,7 @@ static void gsm_control_modem(struct gsm return; dlci = gsm->dlci[addr]; + slen = len; while (gsm_read_ea(&modem, *dp++) == 0) { len--; if (len == 0) @@ -1119,7 +1121,7 @@ static void gsm_control_modem(struct gsm modem |= (brk & 0x7f); } tty = tty_port_tty_get(&dlci->port); - gsm_process_modem(tty, dlci, modem, clen); + gsm_process_modem(tty, dlci, modem, slen); if (tty) { tty_wakeup(tty); tty_kref_put(tty); @@ -1567,6 +1569,7 @@ static void gsm_dlci_data(struct gsm_dlc struct tty_struct *tty; unsigned int modem = 0; int len = clen; + int slen = 0; if (debug & 16) pr_debug("%d bytes for tty\n", len); @@ -1579,12 +1582,14 @@ static void gsm_dlci_data(struct gsm_dlc case 2: /* Asynchronous serial with line state in each frame */ while (gsm_read_ea(&modem, *data++) == 0) { len--; + slen++; if (len == 0) return; } + slen++; tty = tty_port_tty_get(port); if (tty) { - gsm_process_modem(tty, dlci, modem, clen); + gsm_process_modem(tty, dlci, modem, slen); tty_kref_put(tty); } fallthrough; Patches currently in stable-queue which might be from daniel.starke@xxxxxxxxxxx are queue-5.15/tty-n_gsm-fix-encoding-of-control-signal-octet-bit-dv.patch queue-5.15/tty-n_gsm-fix-null-pointer-access-due-to-dlci-release.patch queue-5.15/tty-n_gsm-fix-wrong-modem-processing-in-convergence-layer-type-2.patch queue-5.15/tty-n_gsm-fix-proper-link-termination-after-failed-open.patch queue-5.15/tty-n_gsm-fix-wrong-tty-control-line-for-flow-control.patch queue-5.15/tty-n_gsm-fix-deadlock-in-gsmtty_open.patch