Re: [PATCH net] ipv4: initialize flowi4_flags before calling fib_lookup()

[David Ahern]

On 3/22/16 9:31 AM, Lance Richardson wrote:
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 fl4.flowi4_flags to zero.

Signed-off-by: Lance Richardson <lrich...@redhat.com>
---
  net/ipv4/fib_frontend.c | 1 +
  1 file changed, 1 insertion(+)

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 21add55..896844a 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -304,6 +304,7 @@ __be32 fib_compute_spec_dst(struct sk_buff *skb)
                fl4.flowi4_scope = scope;
                fl4.flowi4_mark = IN_DEV_SRC_VMARK(in_dev) ? skb->mark : 0;
                fl4.flowi4_tun_key.tun_id = 0;
+               fl4.flowi4_flags = 0;
                if (!fib_lookup(net, &fl4, &res, 0))
                        return FIB_RES_PREFSRC(net, res);
        } else {


Fixes: 58189ca7b2741 ("net: Fix vti use case with oif in dst lookups")

I think a more robust solution is to move fl4 to this if case and init 
when it is declared:

        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,
        };