On Mon, Oct 02, 2023 at 03:48:53PM +0300, Andy Shevchenko wrote:
> We can use strnlen() even on early stages and it prevents from
> going over the string boundaries in case it's already too long.
It makes sense to avoid calling strlen() multiple times. I don't have
much opinion one way or another about using strnlen() here, since we
know the string will be terminated.
-Kees
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> ---
> kernel/params.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/params.c b/kernel/params.c
> index 626fa8265932..f8e3c4139854 100644
> --- a/kernel/params.c
> +++ b/kernel/params.c
> @@ -260,7 +260,10 @@ EXPORT_SYMBOL_GPL(param_set_uint_minmax);
>
> int param_set_charp(const char *val, const struct kernel_param *kp)
> {
> - if (strlen(val) > 1024) {
> + size_t len, maxlen = 1024;
> +
> + len = strnlen(val, maxlen + 1);
> + if (len == maxlen + 1) {
> pr_err("%s: string parameter too long\n", kp->name);
> return -ENOSPC;
> }
> @@ -270,7 +273,7 @@ int param_set_charp(const char *val, const struct kernel_param *kp)
> /* This is a hack. We can't kmalloc in early boot, and we
> * don't need to; this mangled commandline is preserved. */
> if (slab_is_available()) {
> - *(char **)kp->arg = kmalloc_parameter(strlen(val)+1);
> + *(char **)kp->arg = kmalloc_parameter(len + 1);
> if (!*(char **)kp->arg)
> return -ENOMEM;
> strcpy(*(char **)kp->arg, val);
> @@ -508,7 +511,7 @@ int param_set_copystring(const char *val, const struct kernel_param *kp)
> {
> const struct kparam_string *kps = kp->str;
>
> - if (strlen(val)+1 > kps->maxlen) {
> + if (strnlen(val, kps->maxlen) == kps->maxlen) {
> pr_err("%s: string doesn't fit in %u chars.\n",
> kp->name, kps->maxlen-1);
> return -ENOSPC;
> --
> 2.40.0.1.gaa8946217a0b
>
--
Kees Cook
