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@xxxxxxxxxx>
---
drivers/usb/gadget/configfs.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c
index b7d2a1313a684..ce3cfa1f36f51 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");
--
2.43.0.472.g3155946c3a-goog
