From cd936621379d513bd768319219840b003a45e729 Mon Sep 17 00:00:00 2001
From: Zhenguo Zhao <Zhenguo.Zhao1@unisoc.com>
Date: Fri, 20 Aug 2021 20:17:46 +0800
Subject: [PATCH] tty: n_gsm: Modify cr bit value when config requester
Git-commit: cd936621379d513bd768319219840b003a45e729
Patch-mainline: v5.16-rc1
References: git-fixes

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@unisoc.com>
Link: https://lore.kernel.org/r/1629461872-26965-2-git-send-email-zhenguo6858@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/tty/n_gsm.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1779,7 +1779,7 @@ static void gsm_queue(struct gsm_mux *gs
 
 	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 *gs
 		}
 		break;
 	case DISC|PF:
-		if (cr == 0)
+		if (cr == 1)
 			goto invalid;
 		if (dlci == NULL || dlci->state == DLCI_CLOSED) {
 			gsm_response(gsm, address, DM);