linux-kernel - [PATCH 2/8] tty: n_gsm: Modify cr bit value when config requester

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Message-Id: <1629461872-26965-2-git-send-email-zhenguo6858@gmail.com>
Date:   Fri, 20 Aug 2021 20:17:46 +0800
From:   Zhenguo Zhao <zhenguo6858@...il.com>
To:     nianfu.bai@...soc.com, gregkh@...uxfoundation.org,
        jirislaby@...nel.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH 2/8] tty: n_gsm: Modify cr bit value when config requester

From: Zhenguo Zhao <Zhenguo.Zhao1@...soc.com>

When n_gsm config "initiator=0",as requester,gsmld will receive dlci
SABM and DISC control command frame,the CR bit value should be 1.

If cr == 0,it will goto invalid,and it can't send UA response
frame and open requster dlci.

        case SABM|PF:
-               if (cr == 0)
+               if (cr == 0) {
+                       printk("gsm_queue invalid\n");
                        goto invalid;
+                       }

Example,gsmld receive dlc0 SABM command frame:f9 03 3f 01 1c f9
but gsmld goto invalid.

Kernel test log:
[  101.794705] c0 gsmld_receive: 00000000: f9 03 3f 01 1c f9
[  101.803341] c0 <-- 0) C: SABM(P)
[  101.811371] c0 gsm_queue invalid

Signed-off-by: Zhenguo Zhao <Zhenguo.Zhao1@...soc.com>
---
 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 5fea02c..becca2c 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1779,7 +1779,7 @@ static void gsm_queue(struct gsm_mux *gsm)
 
 	switch (gsm->control) {
 	case SABM|PF:
-		if (cr == 0)
+		if (cr == 1)
 			goto invalid;
 		if (dlci == NULL)
 			dlci = gsm_dlci_alloc(gsm, address);
@@ -1793,7 +1793,7 @@ static void gsm_queue(struct gsm_mux *gsm)
 		}
 		break;
 	case DISC|PF:
-		if (cr == 0)
+		if (cr == 1)
 			goto invalid;
 		if (dlci == NULL || dlci->state == DLCI_CLOSED) {
 			gsm_response(gsm, address, DM);
-- 
1.9.1