Re: [PATCH] hw/net: prevent potential NULL dereference

[David Gibson <david@gibson.dropbear.id.au>]

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On Wed, May 29, 2024 at 02:07:18PM +0300, Oleg Sviridov wrote:
> Pointer, returned from function 'spapr_vio_find_by_reg', may be NULL and is dereferenced immediately after.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Signed-off-by: Oleg Sviridov <oleg.sviridov@red-soft.ru>
> ---
>  hw/net/spapr_llan.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/hw/net/spapr_llan.c b/hw/net/spapr_llan.c
> index ecb30b7c76..f40b733229 100644
> --- a/hw/net/spapr_llan.c
> +++ b/hw/net/spapr_llan.c
> @@ -770,6 +770,10 @@ static target_ulong h_change_logical_lan_mac(PowerPCCPU *cpu,
>      SpaprVioVlan *dev = VIO_SPAPR_VLAN_DEVICE(sdev);

Hmm... I thought VIO_SPAPR_VLAN_DEVICE() was supposed to abort if sdev
was NULL or not of the right type.  Or have the rules for qom helpers
changed since I wrote this.

>      int i;
>  
> +    if (!dev) {
> +        return H_PARAMETER;
> +    }
> +
>      for (i = 0; i < ETH_ALEN; i++) {
>          dev->nicconf.macaddr.a[ETH_ALEN - i - 1] = macaddr & 0xff;
>          macaddr >>= 8;

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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