[PATCH net-next v2 4/4] s390/ctcm: Convert sprintf/snprintf to scnprintf

Alexandra Winter
2023-06-21T13:50:00Z

This LWN article explains the why scnprintf is preferred over snprintf
in general
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 <wintera@linux.ibm.com>
Signed-off-by: Thorsten Winkler <twinkler@linux.ibm.com>
Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
---
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