Re: [PATCH v2 2/3] lib/bootconfig: check bounds before writing in __xbc_open_brace()

[Steven Rostedt]

On Thu, 12 Mar 2026 19:11:42 +0000
Josh Law <hlcj1234567@xxxxxxxxx> wrote:

> From: Josh Law <objecting@xxxxxxxxxxxxx>
> 
> The bounds check for brace_index happens after the array write.
> While the current call pattern prevents an actual out-of-bounds
> access (the previous call would have returned an error), the
> write-before-check pattern is fragile and would become a real
> out-of-bounds write if the error return were ever not propagated.
> 
> Move the bounds check before the array write so the function is
> self-contained and safe regardless of caller behavior.

This is the only place that increments the index, and the check is >=,
which means even if there was just one space left, it would fail.

As there's no other place that updates brace_index, I don't believe this
patch is needed. It could even replace the >= with ==.

-- Steve


> 
> Signed-off-by: Josh Law <objecting@xxxxxxxxxxxxx>
> ---
>  lib/bootconfig.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/bootconfig.c b/lib/bootconfig.c
> index a1e6a2e14b01..62b4ed7a0ba6 100644
> --- a/lib/bootconfig.c
> +++ b/lib/bootconfig.c
> @@ -532,9 +532,9 @@ static char *skip_spaces_until_newline(char *p)
>  static int __init __xbc_open_brace(char *p)
>  {
>  	/* Push the last key as open brace */
> -	open_brace[brace_index++] = xbc_node_index(last_parent);
>  	if (brace_index >= XBC_DEPTH_MAX)
>  		return xbc_parse_error("Exceed max depth of braces", p);
> +	open_brace[brace_index++] = xbc_node_index(last_parent);
>  
>  	return 0;
>  }