Re: [RFC PATCH 02/20] kho: store incoming radix tree in kho_in

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Missing error handling leads to boot panic
--

commit 84425fcb93791aa9b9c2db978b57ed659f2c9ec2
Author: Pratyush Yadav (Google) <pratyush@kernel.org>

kho: store incoming radix tree in kho_in

This commit stores the incoming radix tree in the kho_in struct to allow
other functions to use it. It also refactors the code to use
kho_get_mem_map_phys() for retrieving the radix tree root from the FDT.

> diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
> --- a/kernel/liveupdate/kexec_handover.c
> +++ b/kernel/liveupdate/kexec_handover.c

[ ... ]

> @@ -1395,24 +1396,10 @@ EXPORT_SYMBOL_GPL(kho_retrieve_subtree);
>  
>  static int __init kho_mem_retrieve(const void *fdt)
>  {
> -	struct kho_radix_tree tree;
> -	const phys_addr_t *mem;
> -	int len;
> -
> -	/* Retrieve the KHO radix tree from passed-in FDT. */
> -	mem = fdt_getprop(fdt, 0, KHO_FDT_MEMORY_MAP_PROP_NAME, &len);
> -
> -	if (!mem || len != sizeof(*mem)) {
> -		pr_err("failed to get preserved KHO memory tree\n");
> -		return -ENOENT;
> -	}
> -
> -	if (!*mem)
> -		return -EINVAL;
> -
> -	tree.root = phys_to_virt(*mem);
> -	mutex_init(&tree.lock);
> -	return kho_radix_walk_tree(&tree, kho_preserved_memory_reserve);
> +	kho_in.radix_tree.root = phys_to_virt(kho_get_mem_map_phys(fdt));

[Severity: High]
Can this lead to a boot panic if kho_get_mem_map_phys() fails?

If kho_get_mem_map_phys() returns 0 on failure, phys_to_virt(0) will likely 
generate a non-NULL pointer. This bypasses the safety validation later when 
walking the tree:

kernel/liveupdate/kexec_handover.c:kho_radix_walk_tree()
    if (WARN_ON_ONCE(!tree->root))
        return -EINVAL;

Walking the tree with this invalid address would then trigger a panic during 
early boot.

I note this issue appears to be fixed later in the series by commit 
80928d5942267 (kho: return virtual address of mem_map), but wanted to point 
out the temporary breakage here.

> +	mutex_init(&kho_in.radix_tree.lock);
> +	return kho_radix_walk_tree(&kho_in.radix_tree,
> +				   kho_preserved_memory_reserve);
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260528004204.1484584-1-jloeser@linux.microsoft.com?part=2