[PATCH] keys, dns: Fix size check of V1 server-list header

[Jarkko Sakkinen]

On Wed Jan 10, 2024 at 11:11 PM EET, David Howells wrote:
>     
> Fix the size check added to dns_resolver_preparse() for the V1 server-list
> header so that it doesn't give EINVAL if the size supplied is the same as
> the size of the header struct (which should be valid).
>
> This can be tested with:
>
>         echo -n -e '\0\0\01\xff\0\0' | keyctl padd dns_resolver desc @p
>
> which will give "add_key: Invalid argument" without this fix.
>
> Fixes: 1997b3cb4217 ("keys, dns: Fix missing size check of V1 server-list header")
> Reported-by: Pengfei Xu <pengfei.xu at intel.com>
> Link: https://lore.kernel.org/r/ZZ4fyY4r3rqgZL+4@xpf.sh.intel.com/
> Signed-off-by: David Howells <dhowells at redhat.com>
> cc: Edward Adam Davis <eadavis at qq.com>
> cc: Linus Torvalds <torvalds at linux-foundation.org>
> cc: Simon Horman <horms at kernel.org>
> Cc: Jarkko Sakkinen <jarkko at kernel.org>
> Cc: Jeffrey E Altman <jaltman at auristor.com>
> Cc: Wang Lei <wang840925 at gmail.com>
> Cc: Jeff Layton <jlayton at redhat.com>
> Cc: Steve French <sfrench at us.ibm.com>
> Cc: Marc Dionne <marc.dionne at auristor.com>
> Cc: "David S. Miller" <davem at davemloft.net>
> Cc: Eric Dumazet <edumazet at google.com>
> Cc: Jakub Kicinski <kuba at kernel.org>
> Cc: Paolo Abeni <pabeni at redhat.com>
> ---
>  net/dns_resolver/dns_key.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
> index f18ca02aa95a..c42ddd85ff1f 100644
> --- a/net/dns_resolver/dns_key.c
> +++ b/net/dns_resolver/dns_key.c
> @@ -104,7 +104,7 @@ dns_resolver_preparse(struct key_preparsed_payload *prep)
>  		const struct dns_server_list_v1_header *v1;
>  
>  		/* It may be a server list. */
> -		if (datalen <= sizeof(*v1))
> +		if (datalen < sizeof(*v1))
>  			return -EINVAL;
>  
>  		v1 = (const struct dns_server_list_v1_header *)data;

Reviewed-by: Jarkko Sakkinen <jarkko at kernel.org>

BR, Jarkko