From 0466e7e693efe6647f23532529a9c41a1fa5f4ac Mon Sep 17 00:00:00 2001
From: Lee Jones <lee@kernel.org>
Date: Wed, 13 Dec 2023 16:42:30 +0000
Subject: usb: gadget: configfs: Replace snprintf() with the safer scnprintf()
variant
There is a general misunderstanding amongst engineers that {v}snprintf()
returns the length of the data *actually* encoded into the destination
array. However, as per the C99 standard {v}snprintf() really returns
the length of the data that *would have been* written if there were
enough space for it. This misunderstanding has led to buffer-overruns
in the past. It's generally considered safer to use the {v}scnprintf()
variants in their place (or even sprintf() in simple cases). So let's
do that.
Link: https://lwn.net/Articles/69419/
Link: https://github.com/KSPP/linux/issues/105
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20231213164246.1021885-2-lee@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/gadget/configfs.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
(limited to 'drivers/usb/gadget/configfs.c')
diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c
index b7d2a1313a68..ce3cfa1f36f5 100644
--- a/drivers/usb/gadget/configfs.c
+++ b/drivers/usb/gadget/configfs.c
@@ -606,10 +606,11 @@ static struct config_group *function_make(
char *instance_name;
int ret;
- ret = snprintf(buf, MAX_NAME_LEN, "%s", name);
- if (ret >= MAX_NAME_LEN)
+ if (strlen(name) >= MAX_NAME_LEN)
return ERR_PTR(-ENAMETOOLONG);
+ scnprintf(buf, MAX_NAME_LEN, "%s", name);
+
func_name = buf;
instance_name = strchr(func_name, '.');
if (!instance_name) {
@@ -701,10 +702,12 @@ static struct config_group *config_desc_make(
int ret;
gi = container_of(group, struct gadget_info, configs_group);
- ret = snprintf(buf, MAX_NAME_LEN, "%s", name);
- if (ret >= MAX_NAME_LEN)
+
+ if (strlen(name) >= MAX_NAME_LEN)
return ERR_PTR(-ENAMETOOLONG);
+ scnprintf(buf, MAX_NAME_LEN, "%s", name);
+
num_str = strchr(buf, '.');
if (!num_str) {
pr_err("Unable to locate . in name.bConfigurationValue\n");
--
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