Subject: [PATCH net-next 4/4] s390/ctcm: Convert sprintf/snprintf to scnprintf

From: Alexandra Winter <[email-masked]>
Date: Tue, 20 Jun 2023 10:34:11 +0200

From: Thorsten Winkler <[email-masked]>

This LWN article explains the rationale for this change
https: //lwn.net/Articles/69419/
Ie. snprintf() returns what *would* be the resulting length,
while scnprintf() returns the actual length.

Note that ctcm_print_statistics() writes the data into the kernel log
and is therefore not suitable for sysfs_emit(). Observable behavior is
not changed, as there may be dependencies.

Reviewed-by: Alexandra Winter <[email-masked]>
Signed-off-by: Thorsten Winkler <[email-masked]>
Signed-off-by: Alexandra Winter <[email-masked]>
---
 drivers/s390/net/ctcm_dbug.c  |  2 +-
 drivers/s390/net/ctcm_main.c  |  6 +++---
 drivers/s390/net/ctcm_main.h  |  1 +
 drivers/s390/net/ctcm_mpc.c   | 18 ++++++++++--------
 drivers/s390/net/ctcm_sysfs.c | 36 +++++++++++++++++------------------
 5 files changed, 33 insertions(+), 30 deletions(-)

diff --git a/drivers/s390/net/ctcm_dbug.c b/drivers/s390/net/ctcm_dbug.c
index f7ec51db3cd6..b6f0e2f114b4 100644
--- a/drivers/s390/net/ctcm_dbug.c
+++ b/drivers/s390/net/ctcm_dbug.c
@@ -70,7 +70,7 @@ void ctcm_dbf_longtext(enum ctcm_dbf_names dbf_nix, int level, char *fmt, ...)
 	if (!debug_level_enabled(ctcm_dbf[dbf_nix].id, level))
 		return;
 	va_start(args, fmt);
-	vsnprintf(dbf_txt_buf, sizeof(dbf_txt_buf), fmt, args);
+	vscnprintf(dbf_txt_buf, sizeof(dbf_txt_buf), fmt, args);
 	va_end(args);
 
 	debug_text_event(ctcm_dbf[dbf_nix].id, level, dbf_txt_buf);
diff --git a/drivers/s390/net/ctcm_main.c b/drivers/s390/net/ctcm_main.c
index e0fdd54bfeb7..79fac5314e67 100644
--- a/drivers/s390/net/ctcm_main.c
+++ b/drivers/s390/net/ctcm_main.c
@@ -1340,7 +1340,7 @@ static int add_channel(struct ccw_device *cdev, enum ctcm_channel_types type,
 					goto nomem_return;
 
 	ch->cdev = cdev;
-	snprintf(ch->id, CTCM_ID_SIZE, "ch-%s", dev_name(&cdev->dev));
+	scnprintf(ch->id, CTCM_ID_SIZE, "ch-%s", dev_name(&cdev->dev));
 	ch->type = type;
 
 	/*
@@ -1505,8 +1505,8 @@ static int ctcm_new_device(struct ccwgroup_device *cgdev)
 
 	type = get_channel_type(&cdev0->id);
 
-	snprintf(read_id, CTCM_ID_SIZE, "ch-%s", dev_name(&cdev0->dev));
-	snprintf(write_id, CTCM_ID_SIZE, "ch-%s", dev_name(&cdev1->dev));
+	scnprintf(read_id, CTCM_ID_SIZE, "ch-%s", dev_name(&cdev0->dev));
+	scnprintf(write_id, CTCM_ID_SIZE, "ch-%s", dev_name(&cdev1->dev));
 
 	ret = add_channel(cdev0, type, priv);
 	if (ret) {
diff --git a/drivers/s390/net/ctcm_main.h b/drivers/s390/net/ctcm_main.h
index 90bd7b3f80c3..25164e8bf13d 100644
--- a/drivers/s390/net/ctcm_main.h
+++ b/drivers/s390/net/ctcm_main.h
@@ -100,6 +100,7 @@ enum ctcm_channel_types {
 #define CTCM_PROTO_MPC		4
 #define CTCM_PROTO_MAX		4
 
+#define CTCM_STATSIZE_LIMIT	64
 #define CTCM_BUFSIZE_LIMIT	65535
 #define CTCM_BUFSIZE_DEFAULT	32768
 #define MPC_BUFSIZE_DEFAULT	CTCM_BUFSIZE_LIMIT
diff --git a/drivers/s390/net/ctcm_mpc.c b/drivers/s390/net/ctcm_mpc.c
index 8ac213a55141..64996c86defc 100644
--- a/drivers/s390/net/ctcm_mpc.c
+++ b/drivers/s390/net/ctcm_mpc.c
@@ -144,9 +144,9 @@ void ctcmpc_dumpit(char *buf, int len)
 
 	for (ct = 0; ct < len; ct++, ptr++, rptr++) {
 		if (sw == 0) {
-			sprintf(addr, "%16.16llx", (__u64)rptr);
+			scnprintf(addr, sizeof(addr), "%16.16llx", (__u64)rptr);
 
-			sprintf(boff, "%4.4X", (__u32)ct);
+			scnprintf(boff, sizeof(boff), "%4.4X", (__u32)ct);
 			bhex[0] = '\0';
 			basc[0] = '\0';
 		}
@@ -155,7 +155,7 @@ void ctcmpc_dumpit(char *buf, int len)
 		if (sw == 8)
 			strcat(bhex, "	");
 
-		sprintf(tbuf, "%2.2llX", (__u64)*ptr);
+		scnprintf(tbuf, sizeof(tbuf), "%2.2llX", (__u64)*ptr);
 
 		tbuf[2] = '\0';
 		strcat(bhex, tbuf);
@@ -171,8 +171,8 @@ void ctcmpc_dumpit(char *buf, int len)
 			continue;
 		if ((strcmp(duphex, bhex)) != 0) {
 			if (dup != 0) {
-				sprintf(tdup,
-					"Duplicate as above to %s", addr);
+				scnprintf(tdup, sizeof(tdup),
+					  "Duplicate as above to %s", addr);
 				ctcm_pr_debug("		       --- %s ---\n",
 						tdup);
 			}
@@ -197,14 +197,16 @@ void ctcmpc_dumpit(char *buf, int len)
 			strcat(basc, " ");
 		}
 		if (dup != 0) {
-			sprintf(tdup, "Duplicate as above to %s", addr);
+			scnprintf(tdup, sizeof(tdup),
+				  "Duplicate as above to %s", addr);
 			ctcm_pr_debug("		       --- %s ---\n", tdup);
 		}
 		ctcm_pr_debug("   %s (+%s) : %s  [%s]\n",
 					addr, boff, bhex, basc);
 	} else {
 		if (dup >= 1) {
-			sprintf(tdup, "Duplicate as above to %s", addr);
+			scnprintf(tdup, sizeof(tdup),
+				  "Duplicate as above to %s", addr);
 			ctcm_pr_debug("		       --- %s ---\n", tdup);
 		}
 		if (dup != 0) {
@@ -291,7 +293,7 @@ static struct net_device *ctcmpc_get_dev(int port_num)
 	struct net_device *dev;
 	struct ctcm_priv *priv;
 
-	sprintf(device, "%s%i", MPC_DEVICE_NAME, port_num);
+	scnprintf(device, sizeof(device), "%s%i", MPC_DEVICE_NAME, port_num);
 
 	dev = __dev_get_by_name(&init_net, device);
 
diff --git a/drivers/s390/net/ctcm_sysfs.c b/drivers/s390/net/ctcm_sysfs.c
index 98680c2cc4e4..0c5d8a3eaa2e 100644
--- a/drivers/s390/net/ctcm_sysfs.c
+++ b/drivers/s390/net/ctcm_sysfs.c
@@ -86,24 +86,24 @@ static void ctcm_print_statistics(struct ctcm_priv *priv)
 		return;
 	p = sbuf;
 
-	p += sprintf(p, "  Device FSM state: %s\n",
-		     fsm_getstate_str(priv->fsm));
-	p += sprintf(p, "  RX channel FSM state: %s\n",
-		     fsm_getstate_str(priv->channel[CTCM_READ]->fsm));
-	p += sprintf(p, "  TX channel FSM state: %s\n",
-		     fsm_getstate_str(priv->channel[CTCM_WRITE]->fsm));
-	p += sprintf(p, "  Max. TX buffer used: %ld\n",
-		     priv->channel[WRITE]->prof.maxmulti);
-	p += sprintf(p, "  Max. chained SKBs: %ld\n",
-		     priv->channel[WRITE]->prof.maxcqueue);
-	p += sprintf(p, "  TX single write ops: %ld\n",
-		     priv->channel[WRITE]->prof.doios_single);
-	p += sprintf(p, "  TX multi write ops: %ld\n",
-		     priv->channel[WRITE]->prof.doios_multi);
-	p += sprintf(p, "  Netto bytes written: %ld\n",
-		     priv->channel[WRITE]->prof.txlen);
-	p += sprintf(p, "  Max. TX IO-time: %u\n",
-		     jiffies_to_usecs(priv->channel[WRITE]->prof.tx_time));
+	p += scnprintf(p, CTCM_STATSIZE_LIMIT, "  Device FSM state: %s\n",
+		       fsm_getstate_str(priv->fsm));
+	p += scnprintf(p, CTCM_STATSIZE_LIMIT, "  RX channel FSM state: %s\n",
+		       fsm_getstate_str(priv->channel[CTCM_READ]->fsm));
+	p += scnprintf(p, CTCM_STATSIZE_LIMIT, "  TX channel FSM state: %s\n",
+		       fsm_getstate_str(priv->channel[CTCM_WRITE]->fsm));
+	p += scnprintf(p, CTCM_STATSIZE_LIMIT, "  Max. TX buffer used: %ld\n",
+		       priv->channel[WRITE]->prof.maxmulti);
+	p += scnprintf(p, CTCM_STATSIZE_LIMIT, "  Max. chained SKBs: %ld\n",
+		       priv->channel[WRITE]->prof.maxcqueue);
+	p += scnprintf(p, CTCM_STATSIZE_LIMIT, "  TX single write ops: %ld\n",
+		       priv->channel[WRITE]->prof.doios_single);
+	p += scnprintf(p, CTCM_STATSIZE_LIMIT, "  TX multi write ops: %ld\n",
+		       priv->channel[WRITE]->prof.doios_multi);
+	p += scnprintf(p, CTCM_STATSIZE_LIMIT, "  Netto bytes written: %ld\n",
+		       priv->channel[WRITE]->prof.txlen);
+	p += scnprintf(p, CTCM_STATSIZE_LIMIT, "  Max. TX IO-time: %u\n",
+		       jiffies_to_usecs(priv->channel[WRITE]->prof.tx_time));
 
 	printk(KERN_INFO "Statistics for %s:\n%s",
 				priv->channel[CTCM_WRITE]->netdev->name, sbuf);
-- 
2.39.2