kobject: Replace strlcpy with strscpy

strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().

Direct replacement is safe here since return value of -errno
is used to check for truncation instead of sizeof(dest).

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89

Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230831140104.207019-1-azeemshaikh38@gmail.com
Signed-off-by: Kees Cook <keescook@chromium.org>

diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
index 7c44b7ae4c5c34bb586a9c362ed9b06913b54bb1..fb9a2f06dd1e79db0e5db17362c88152790e2b36 100644 (file)
--- a/lib/kobject_uevent.c
+++ b/lib/kobject_uevent.c
@@ -254,10 +254,10 @@ static int init_uevent_argv(struct kobj_uevent_env *env, const char *subsystem)
        int buffer_size = sizeof(env->buf) - env->buflen;
        int len;
 
-       len = strlcpy(&env->buf[env->buflen], subsystem, buffer_size);
-       if (len >= buffer_size) {
-               pr_warn("init_uevent_argv: buffer size of %d too small, needed %d\n",
-                       buffer_size, len);
+       len = strscpy(&env->buf[env->buflen], subsystem, buffer_size);
+       if (len < 0) {
+               pr_warn("%s: insufficient buffer space (%u left) for %s\n",
+                       __func__, buffer_size, subsystem);
                return -ENOMEM;
        }