netdev - Re: [PATCH net] ipv4: initialize flowi4_flags before calling fib

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Date:	Tue, 22 Mar 2016 14:58:59 -0400 (EDT)
From:	Lance Richardson <lrichard@...hat.com>
To:	netdev@...r.kernel.org
Cc:	dsa@...ulusnetworks.com
Subject: Re: [PATCH net] ipv4: initialize flowi4_flags before calling
 fib_lookup()

Apologies, that should have been [PATCH v2 net].

----- Original Message -----
> From: "Lance Richardson" <lrichard@...hat.com>
> To: netdev@...r.kernel.org
> Cc: dsa@...ulusnetworks.com
> Sent: Tuesday, March 22, 2016 2:56:57 PM
> Subject: [PATCH net] ipv4: initialize flowi4_flags before calling fib_lookup()
> 
> Field fl4.flowi4_flags is not initialized in fib_compute_spec_dst()
> before calling fib_lookup(), which means fib_table_lookup() is
> using non-deterministic data at this line:
> 
> 	if (!(flp->flowi4_flags & FLOWI_FLAG_SKIP_NH_OIF)) {
> 
> Fix by initializing the entire fl4 structure, which will prevent
> similar issues as fields are added in the future by ensuring that
> all fields are initialized to zero unless explicitly initialized
> to another value.
> 
> Fixes: 58189ca7b2741 ("net: Fix vti use case with oif in dst lookups")
> Suggested-by: David Ahern <dsa@...ulusnetworks.com>
> Signed-off-by: Lance Richardson <lrichard@...hat.com>
> ---
>  net/ipv4/fib_frontend.c | 16 +++++++---------
>  1 file changed, 7 insertions(+), 9 deletions(-)
> 
> diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
> index 21add55..8a9246d 100644
> --- a/net/ipv4/fib_frontend.c
> +++ b/net/ipv4/fib_frontend.c
> @@ -280,7 +280,6 @@ __be32 fib_compute_spec_dst(struct sk_buff *skb)
>  	struct in_device *in_dev;
>  	struct fib_result res;
>  	struct rtable *rt;
> -	struct flowi4 fl4;
>  	struct net *net;
>  	int scope;
>  
> @@ -296,14 +295,13 @@ __be32 fib_compute_spec_dst(struct sk_buff *skb)
>  
>  	scope = RT_SCOPE_UNIVERSE;
>  	if (!ipv4_is_zeronet(ip_hdr(skb)->saddr)) {
> -		fl4.flowi4_oif = 0;
> -		fl4.flowi4_iif = LOOPBACK_IFINDEX;
> -		fl4.daddr = ip_hdr(skb)->saddr;
> -		fl4.saddr = 0;
> -		fl4.flowi4_tos = RT_TOS(ip_hdr(skb)->tos);
> -		fl4.flowi4_scope = scope;
> -		fl4.flowi4_mark = IN_DEV_SRC_VMARK(in_dev) ? skb->mark : 0;
> -		fl4.flowi4_tun_key.tun_id = 0;
> +		struct flowi4 fl4 = {
> +			.flowi4_iif = LOOPBACK_IFINDEX,
> +			.daddr = ip_hdr(skb)->saddr,
> +			.flowi4_tos = RT_TOS(ip_hdr(skb)->tos),
> +			.flowi4_scope = scope,
> +			.flowi4_mark = IN_DEV_SRC_VMARK(in_dev) ? skb->mark : 0,
> +		};
>  		if (!fib_lookup(net, &fl4, &res, 0))
>  			return FIB_RES_PREFSRC(net, res);
>  	} else {
> --
> 2.5.5
> 
>