From: Daniel Starke <daniel.starke@xxxxxxxxxxx> n_gsm has a minimal protocol overhead of 7 bytes. The current code already checks whether the configured MRU/MTU size is at least one byte more than this. Introduce the macro MIN_MTU to make this value more obvious. Signed-off-by: Daniel Starke <daniel.starke@xxxxxxxxxxx> --- drivers/tty/n_gsm.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) v2 -> v3: No changes. Link: https://lore.kernel.org/all/20221024130114.2070-1-daniel.starke@xxxxxxxxxxx/ diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index 5e516f5cac5a..570c40a3d78f 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -89,6 +89,7 @@ module_param(debug, int, 0600); */ #define MAX_MRU 1500 #define MAX_MTU 1500 +#define MIN_MTU (PROT_OVERHEAD + 1) /* SOF, ADDR, CTRL, LEN1, LEN2, ..., FCS, EOF */ #define PROT_OVERHEAD 7 #define GSM_NET_TX_TIMEOUT (HZ*10) @@ -2712,7 +2713,9 @@ static int gsm_config(struct gsm_mux *gsm, struct gsm_config *c) if ((c->adaption != 1 && c->adaption != 2) || c->k) return -EOPNOTSUPP; /* Check the MRU/MTU range looks sane */ - if (c->mru > MAX_MRU || c->mtu > MAX_MTU || c->mru < 8 || c->mtu < 8) + if (c->mru < MIN_MTU || c->mtu < MIN_MTU) + return -EINVAL; + if (c->mru > MAX_MRU || c->mtu > MAX_MTU) return -EINVAL; if (c->n2 > 255) return -EINVAL; @@ -3296,7 +3299,7 @@ static int gsm_create_network(struct gsm_dlci *dlci, struct gsm_netconfig *nc) return -ENOMEM; } net->mtu = dlci->gsm->mtu; - net->min_mtu = 8; + net->min_mtu = MIN_MTU; net->max_mtu = dlci->gsm->mtu; mux_net = netdev_priv(net); mux_net->dlci = dlci; -- 2.34.1
