Re: [PATCH v2] cmd: abootimg: Prevent use of unintialised variable

[Mattijs Korpershoek <mkorpershoek@kernel.org>]

Hi Andrew,

Thank you for the patch.

On Wed, Jun 25, 2025 at 16:52, Andrew Goodbody <andrew.goodbody@linaro.org> wrote:

> vhdr can be used when not initialised so detect this condition
> and exit early to prevent the problem.
>
> This issue was found with Smatch.
>
> Fixes: 636da2039aea (android: boot: support boot image header version 3 and 4)
> Signed-off-by: Andrew Goodbody <andrew.goodbody@linaro.org>
> ---
> Changes in v2:
> - Add unmap_sysmem(hdr) in the new exit path
> - Link to v1: https://lore.kernel.org/r/20250625-abootimg_fix-v1-1-ce1645ac9879@linaro.org
> ---
>  cmd/abootimg.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/cmd/abootimg.c b/cmd/abootimg.c
> index ae7a1a7c83b..31620aa3cfa 100644
> --- a/cmd/abootimg.c
> +++ b/cmd/abootimg.c
> @@ -98,18 +98,20 @@ static int abootimg_get_dtb_load_addr(int argc, char *const argv[])
>  	const struct andr_vnd_boot_img_hdr *vhdr;
>  
>  	hdr = map_sysmem(abootimg_addr(), sizeof(*hdr));
> -	if (get_avendor_bootimg_addr() != -1)
> +	if (get_avendor_bootimg_addr() != -1) {
>  		vhdr = map_sysmem(get_avendor_bootimg_addr(), sizeof(*vhdr));
> +	} else {
> +		unmap_sysmem(hdr);
> +		return CMD_RET_FAILURE;
> +	}

It's valid for avendor_bootimg_adr() to be -1.
This is the case for boot image v2 and lower, where there is no
boot_vendor partition. (so there is no valid vhdr).

Per my understanding vhdr* is NULL if left unintialised. (I might be
wrong, please let me know).

android_image_get_data() handles the case where vendor_boot_hdr is NULL:
"""
	if (((struct andr_boot_img_hdr_v0 *)boot_hdr)->header_version > 2) {
		if (!vendor_boot_hdr) {
			printf("For boot header v3+ vendor boot image has to be provided\n");
			return false;
		}
"""

So I don't think we should early return here.
If we do, we will probably break boot image v2 support.

>  
>  	if (!android_image_get_data(hdr, vhdr, &img_data)) {
> -		if (get_avendor_bootimg_addr() != -1)
> -			unmap_sysmem(vhdr);
> +		unmap_sysmem(vhdr);
>  		unmap_sysmem(hdr);
>  		return CMD_RET_FAILURE;
>  	}
>  
> -	if (get_avendor_bootimg_addr() != -1)
> -		unmap_sysmem(vhdr);
> +	unmap_sysmem(vhdr);
>  	unmap_sysmem(hdr);
>  
>  	if (img_data.header_version < 2) {
>
> ---
> base-commit: 903eb123236ccbd8ef05d43507a2a910b785bd56
> change-id: 20250625-abootimg_fix-51600dc8356a
>
> Best regards,
> -- 
> Andrew Goodbody <andrew.goodbody@linaro.org>