octeontx2-af: Add validation for lmac type

Upon physical link change, firmware reports to the kernel about the
change along with the details like speed, lmac_type_id, etc.
Kernel derives lmac_type based on lmac_type_id received from firmware.

In a few scenarios, firmware returns an invalid lmac_type_id, which
is resulting in below kernel panic. This patch adds the missing
validation of the lmac_type_id field.

Internal error: Oops: 96000005 [#1] PREEMPT SMP
[   35.321595] Modules linked in:
[   35.328982] CPU: 0 PID: 31 Comm: kworker/0:1 Not tainted
5.4.210-g2e3169d8e1bc-dirty #17
[   35.337014] Hardware name: Marvell CN103XX board (DT)
[   35.344297] Workqueue: events work_for_cpu_fn
[   35.352730] pstate: 40400089 (nZcv daIf +PAN -UAO)
[   35.360267] pc : strncpy+0x10/0x30
[   35.366595] lr : cgx_link_change_handler+0x90/0x180

Fixes: 61071a8 ("octeontx2-af: Forward CGX link notifications to PFs")
Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Signed-off-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
Signed-off-by: Sai Krishna <saikrishnag@marvell.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: Hariprasad Kelam

drivers/net/ethernet/marvell/octeontx2/af/cgx.c

@@ -1231,6 +1231,14 @@ static inline void link_status_user_format(u64 lstat,
 	linfo->an = FIELD_GET(RESP_LINKSTAT_AN, lstat);
 	linfo->fec = FIELD_GET(RESP_LINKSTAT_FEC, lstat);
 	linfo->lmac_type_id = FIELD_GET(RESP_LINKSTAT_LMAC_TYPE, lstat);
+
+	if (linfo->lmac_type_id >= LMAC_MODE_MAX) {
+		dev_err(&cgx->pdev->dev, "Unknown lmac_type_id %d reported by firmware on cgx port%d:%d",
+			linfo->lmac_type_id, cgx->cgx_id, lmac_id);
+		strncpy(linfo->lmac_type, "Unknown", LMACTYPE_STR_LEN - 1);
+		return;
+	}
+
 	lmac_string = cgx_lmactype_string[linfo->lmac_type_id];
 	strncpy(linfo->lmac_type, lmac_string, LMACTYPE_STR_LEN - 1);
 }