Re: [for-4.18][PATCH] xen/arm: Check return code from recursive calls to scan_pfdt_node()

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi Michal,

> On 16 Oct 2023, at 14:45, Michal Orzel <michal.orzel@xxxxxxx> wrote:
> 
> At the moment, we do not check a return code from scan_pfdt_node()
> called recursively. This means that any issue that may occur while
> parsing and copying the passthrough nodes is hidden and Xen continues
> to boot a domain despite errors. This may lead to incorrect device tree
> generation and various guest issues (e.g. trap on attempt to access MMIO
> not mapped in P2M). Fix it.
> 
> Fixes: 669ecdf8d6cd ("xen/arm: copy dtb fragment to guest dtb")
> Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>

Good finding :-)

Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

Cheers
Bertrand

> ---
> @Henry:
> This is a bug fix, so I think we should have it in 4.18 given the possible
> consequences I described in the commit msg. I don't see any risks as this 
> change
> only checks the return code for an error.
> ---
> xen/arch/arm/domain_build.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index 24c9019cc43c..49792dd590ee 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -2872,8 +2872,11 @@ static int __init scan_pfdt_node(struct kernel_info 
> *kinfo, const void *pfdt,
>     node_next = fdt_first_subnode(pfdt, nodeoff);
>     while ( node_next > 0 )
>     {
> -        scan_pfdt_node(kinfo, pfdt, node_next, address_cells, size_cells,
> -                       scan_passthrough_prop);
> +        rc = scan_pfdt_node(kinfo, pfdt, node_next, address_cells, 
> size_cells,
> +                            scan_passthrough_prop);
> +        if ( rc )
> +            return rc;
> +
>         node_next = fdt_next_subnode(pfdt, node_next);
>     }
> 
> -- 
> 2.25.1
>