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

Paolo Abeni
2023-06-23T09:56:18Z

On Wed, 2023-06-21 at 15:49 +0200, Alexandra Winter wrote:
> From: Thorsten Winkler <twinkler@linux.ibm.com>
>
> 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);

Not strictly related to this series, but it looks like there is
opportunity for more cleanups? e.g. move legacy printk to pr_info(),
etc...

The series LGTM.

Thanks,

Paolo