Defer the generation of the first hash secret for the ipv4 fragmentation
cache as late as possible.
ip4_frags.rnd gets initial seeded by inet_frags_init and regulary
reseeded by inet_frag_secret_rebuild. Either we call ipqhashfn directly
from ip_fragment.c in which case we initialize the secret directly.
If we first get called by inet_frag_secret_rebuild we install a new secret
by a manual call to get_random_bytes. This secret will be overwritten
as soon as the first call to ipqhashfn happens. This is safe because we
won't race while publishing the new secrets with anyone else.
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Signed-off-by: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx>
---
net/ipv4/ip_fragment.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index b66910a..2481993 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -106,6 +106,7 @@ struct ip4_create_arg {
static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)
{
+ net_get_random_once(&ip4_frags.rnd, sizeof(ip4_frags.rnd));
return jhash_3words((__force u32)id << 16 | prot,
(__force u32)saddr, (__force u32)daddr,
ip4_frags.rnd) & (INETFRAGS_HASHSZ - 1);
--
1.8.3.1
--
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