[PATCH v5 09/11] FIT: fit_open: make filename handling more robust

[Sascha Hauer]

On Mon, Aug 18, 2025 at 07:26:17PM +0200, Marco Felsch wrote:
> Require the filename to start at the root '/' directory and resolve any
> possible link to make the filename handling more robust.
> 
> This is in preparation of adding cached fit_open support.
> 
> Signed-off-by: Marco Felsch <m.felsch at pengutronix.de>
> ---
>  common/image-fit.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/common/image-fit.c b/common/image-fit.c
> index 0067f46e60bc954b418aef3398e2c10856b41c02..1cb407d4d86cb3d0a643149bb08c46caadcd56fe 100644
> --- a/common/image-fit.c
> +++ b/common/image-fit.c
> @@ -972,12 +972,25 @@ struct fit_handle *fit_open_buf(const void *buf, size_t size, bool verbose,
>   *
>   * Return: A handle to a FIT image or a ERR_PTR
>   */
> -struct fit_handle *fit_open(const char *filename, bool verbose,
> +struct fit_handle *fit_open(const char *_filename, bool verbose,
>  			    enum bootm_verify verify, loff_t max_size)
>  {
>  	struct fit_handle *handle;
> +	char *filename;
>  	int ret;
>  
> +	if (*_filename != '/') {
> +		pr_err("The FIT filename must start with '/'\n");
> +		return ERR_PTR(-EINVAL);
> +	}

Drop this. We want to be able to call fit_open() with relative pathes...

> +
> +	/* dirfd is ignored, since _filename is absolute */
> +	filename = canonicalize_path(AT_FDCWD, _filename);

...and you are calling canonicalize_path() anyway which gives you an
absolute path from the potentially relative input path.

> +	if (!filename) {
> +		pr_err("Failed to resolve %s with %s\n", _filename, strerror(errno));

		pr_err("Cannot open %s: %m\n", filename);

I think the "Failed to resolve" is misleading here.

Sascha

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