Messages in this thread Patch in this message | | | From | Ben Hutchings <> | Date | Tue, 08 Jul 2014 20:01:50 +0100 | Subject | [PATCH 3.2 112/125] net: fix inet_getid() and ipv6_select_ident() bugs |
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3.2.61-rc1 review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet <edumazet@google.com>
[ Upstream commit 39c36094d78c39e038c1e499b2364e13bce36f54 ]
I noticed we were sending wrong IPv4 ID in TCP flows when MTU discovery is disabled. Note how GSO/TSO packets do not have monotonically incrementing ID.
06:37:41.575531 IP (id 14227, proto: TCP (6), length: 4396) 06:37:41.575534 IP (id 14272, proto: TCP (6), length: 65212) 06:37:41.575544 IP (id 14312, proto: TCP (6), length: 57972) 06:37:41.575678 IP (id 14317, proto: TCP (6), length: 7292) 06:37:41.575683 IP (id 14361, proto: TCP (6), length: 63764)
It appears I introduced this bug in linux-3.1.
inet_getid() must return the old value of peer->ip_id_count, not the new one.
Lets revert this part, and remove the prevention of a null identification field in IPv6 Fragment Extension Header, which is dubious and not even done properly.
Fixes: 87c48fa3b463 ("ipv6: make fragment identifications less predictable") Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- include/net/inetpeer.h | 9 +-------- net/ipv6/ip6_output.c | 11 +++-------- 2 files changed, 4 insertions(+), 16 deletions(-)
--- a/include/net/inetpeer.h +++ b/include/net/inetpeer.h @@ -115,16 +115,9 @@ static inline void inet_peer_refcheck(co /* can be called with or without local BH being disabled */ static inline int inet_getid(struct inet_peer *p, int more) { - int old, new; more++; inet_peer_refcheck(p); - do { - old = atomic_read(&p->ip_id_count); - new = old + more; - if (!new) - new = 1; - } while (atomic_cmpxchg(&p->ip_id_count, old, new) != old); - return new; + return atomic_add_return(more, &p->ip_id_count) - more; } #endif /* _NET_INETPEER_H */ --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -612,7 +612,7 @@ int ip6_find_1stfragopt(struct sk_buff * void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt) { static atomic_t ipv6_fragmentation_id; - int old, new; + int ident; if (rt && !(rt->dst.flags & DST_NOPEER)) { struct inet_peer *peer; @@ -625,13 +625,8 @@ void ipv6_select_ident(struct frag_hdr * return; } } - do { - old = atomic_read(&ipv6_fragmentation_id); - new = old + 1; - if (!new) - new = 1; - } while (atomic_cmpxchg(&ipv6_fragmentation_id, old, new) != old); - fhdr->identification = htonl(new); + ident = atomic_inc_return(&ipv6_fragmentation_id); + fhdr->identification = htonl(ident); } int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
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