From 535bf600de75a859698892ee873521a48d289ec1 Mon Sep 17 00:00:00 2001 From: Daniel Starke Date: Thu, 14 Apr 2022 02:42:13 -0700 Subject: [PATCH] tty: n_gsm: fix insufficient txframe size 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 5.7.2 states that the maximum frame size (N1) refers to the length of the information field (i.e. user payload). However, 'txframe' stores the whole frame including frame header, checksum and start/end flags. We also need to consider the byte stuffing overhead. Define constant for the protocol overhead and adjust the 'txframe' size calculation accordingly to reserve enough space for a complete mux frame including byte stuffing for advanced option mode. Note that no byte stuffing is applied to the start and end flag. Also use MAX_MTU instead of MAX_MRU as this buffer is used for data transmission. Fixes: e1eaea46bb40 ("tty: n_gsm line discipline") Cc: stable@vger.kernel.org Signed-off-by: Daniel Starke Link: https://lore.kernel.org/r/20220414094225.4527-8-daniel.starke@siemens.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/n_gsm.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index 2e3da8a..cc90b03 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -73,6 +73,8 @@ module_param(debug, int, 0600); */ #define MAX_MRU 1500 #define MAX_MTU 1500 +/* SOF, ADDR, CTRL, LEN1, LEN2, ..., FCS, EOF */ +#define PROT_OVERHEAD 7 #define GSM_NET_TX_TIMEOUT (HZ*10) /* @@ -2264,7 +2266,7 @@ static struct gsm_mux *gsm_alloc_mux(void) kfree(gsm); return NULL; } - gsm->txframe = kmalloc(2 * MAX_MRU + 2, GFP_KERNEL); + gsm->txframe = kmalloc(2 * (MAX_MTU + PROT_OVERHEAD - 1), GFP_KERNEL); if (gsm->txframe == NULL) { kfree(gsm->buf); kfree(gsm); -- 2.7.4