From: Daniel Starke <daniel.starke@xxxxxxxxxxx> [ Upstream commit f30e10caa80aa1f35508bc17fc302dbbde9a833c ] n_gsm is based on the 3GPP 07.010 and its newer version is the 3GPP 27.010. See https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1516 The changes from 07.010 to 27.010 are non-functional. Therefore, I refer to the newer 27.010 here. Chapter 5.7.3 states that the valid range for the maximum number of retransmissions (N2) is from 0 to 255 (both including). gsm_dlci_t1() handles this number incorrectly by performing N2 - 1 retransmission attempts. Setting N2 to zero results in more than 255 retransmission attempts. Fix gsm_dlci_t1() to comply with 3GPP 27.010. Fixes: e1eaea46bb40 ("tty: n_gsm line discipline") Signed-off-by: Daniel Starke <daniel.starke@xxxxxxxxxxx> Link: https://lore.kernel.org/r/20220707113223.3685-1-daniel.starke@xxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/tty/n_gsm.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index 969c0de788f8..3f100f7abdb7 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -1550,8 +1550,8 @@ static void gsm_dlci_t1(struct timer_list *t) switch (dlci->state) { case DLCI_OPENING: - dlci->retries--; if (dlci->retries) { + dlci->retries--; gsm_command(dlci->gsm, dlci->addr, SABM|PF); mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100); } else if (!dlci->addr && gsm->control == (DM | PF)) { @@ -1566,8 +1566,8 @@ static void gsm_dlci_t1(struct timer_list *t) break; case DLCI_CLOSING: - dlci->retries--; if (dlci->retries) { + dlci->retries--; gsm_command(dlci->gsm, dlci->addr, DISC|PF); mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100); } else -- 2.35.1
