On Sat, 2011-09-10 at 16:59 +0200, Eric Dumazet wrote: > Le samedi 10 septembre 2011 à 02:30 +0100, Ben Hutchings a écrit : > > Is there any chance that this change could be backported to the 2.6.32.y > > longterm branch: > > > > commit 87c48fa3b4630905f98268dde838ee43626a060c > > Author: Eric Dumazet <eric.duma...@gmail.com> > > Date: Thu Jul 21 21:25:58 2011 -0700 > > > > ipv6: make fragment identifications less predictable > > > > I suspect that it's very much dependent on the earlier changes to dst > > and inetpeer, right? > > > > Ben. > > > > Hi Ben > > This was the fix meant for next kernels (>= 3.1) , not suitable for a > backport. > > I sent a patch for the backport, and David replied he would take care of > stable submission.
However, he doesn't submit patches for 'longterm' series any more. > He did so, since it was included in 3.0-stable tree (>= 3.0.2) > > http://permalink.gmane.org/gmane.linux.kernel.stable/16086 > > This one is far more easy to be included in old kernels ;) Right. So does this the following look right for 2.6.32? By the way, use of a hash table the size of a cache line doesn't seem likely to be much better than a spinlock. Still, anyone who cares about performance will avoid fragmentation since they are almost certainly going to lose TX checksum offload. Ben. From: Eric Dumazet <eric.duma...@gmail.com> Date: Mon, 8 Aug 2011 23:44:00 -0700 Subject: [PATCH] ipv6: make fragment identifications less predictable [ Backport of upstream commit 87c48fa3b4630905f98268dde838ee43626a060c ] Fernando Gont reported current IPv6 fragment identification generation was not secure, because using a very predictable system-wide generator, allowing various attacks. IPv4 uses inetpeer cache to address this problem and to get good performance. We'll use this mechanism when IPv6 inetpeer is stable enough in linux-3.1 For the time being, we use jhash on destination address to provide less predictable identifications. Also remove a spinlock and use cmpxchg() to get better SMP performance. Reported-by: Fernando Gont <ferna...@gont.com.ar> Signed-off-by: Eric Dumazet <eric.duma...@gmail.com> Signed-off-by: David S. Miller <da...@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gre...@suse.de> [bwh: Backport further to 2.6.32] Signed-off-by: Ben Hutchings <b...@decadent.org.uk> --- include/net/ipv6.h | 12 +----------- include/net/transp_v6.h | 2 ++ net/ipv6/af_inet6.c | 2 ++ net/ipv6/ip6_output.c | 40 +++++++++++++++++++++++++++++++++++----- net/ipv6/udp.c | 2 +- 5 files changed, 41 insertions(+), 17 deletions(-) diff --git a/include/net/ipv6.h b/include/net/ipv6.h index 639bbf0..52d86da 100644 --- a/include/net/ipv6.h +++ b/include/net/ipv6.h @@ -449,17 +449,7 @@ static inline int ipv6_addr_diff(const struct in6_addr *a1, const struct in6_add return __ipv6_addr_diff(a1, a2, sizeof(struct in6_addr)); } -static __inline__ void ipv6_select_ident(struct frag_hdr *fhdr) -{ - static u32 ipv6_fragmentation_id = 1; - static DEFINE_SPINLOCK(ip6_id_lock); - - spin_lock_bh(&ip6_id_lock); - fhdr->identification = htonl(ipv6_fragmentation_id); - if (++ipv6_fragmentation_id == 0) - ipv6_fragmentation_id = 1; - spin_unlock_bh(&ip6_id_lock); -} +extern void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt); /* * Prototypes exported by ipv6 diff --git a/include/net/transp_v6.h b/include/net/transp_v6.h index d65381c..8beefe1 100644 --- a/include/net/transp_v6.h +++ b/include/net/transp_v6.h @@ -16,6 +16,8 @@ extern struct proto tcpv6_prot; struct flowi; +extern void initialize_hashidentrnd(void); + /* extention headers */ extern int ipv6_exthdrs_init(void); extern void ipv6_exthdrs_exit(void); diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c index e127a32..835590d 100644 --- a/net/ipv6/af_inet6.c +++ b/net/ipv6/af_inet6.c @@ -1073,6 +1073,8 @@ static int __init inet6_init(void) goto out; } + initialize_hashidentrnd(); + err = proto_register(&tcpv6_prot, 1); if (err) goto out; diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index eca3ef7..43c31f9 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -604,6 +604,35 @@ int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr) return offset; } +static u32 hashidentrnd __read_mostly; +#define FID_HASH_SZ 16 +static u32 ipv6_fragmentation_id[FID_HASH_SZ]; + +void __init initialize_hashidentrnd(void) +{ + get_random_bytes(&hashidentrnd, sizeof(hashidentrnd)); +} + +static u32 __ipv6_select_ident(const struct in6_addr *addr) +{ + u32 newid, oldid, hash = jhash2((u32 *)addr, 4, hashidentrnd); + u32 *pid = &ipv6_fragmentation_id[hash % FID_HASH_SZ]; + + do { + oldid = *pid; + newid = oldid + 1; + if (!(hash + newid)) + newid++; + } while (cmpxchg(pid, oldid, newid) != oldid); + + return hash + newid; +} + +void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt) +{ + fhdr->identification = htonl(__ipv6_select_ident(&rt->rt6i_dst.addr)); +} + static int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *)) { struct sk_buff *frag; @@ -689,7 +718,7 @@ static int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *)) skb_reset_network_header(skb); memcpy(skb_network_header(skb), tmp_hdr, hlen); - ipv6_select_ident(fh); + ipv6_select_ident(fh, rt); fh->nexthdr = nexthdr; fh->reserved = 0; fh->frag_off = htons(IP6_MF); @@ -835,7 +864,7 @@ slow_path: fh->nexthdr = nexthdr; fh->reserved = 0; if (!frag_id) { - ipv6_select_ident(fh); + ipv6_select_ident(fh, rt); frag_id = fh->identification; } else fh->identification = frag_id; @@ -1039,7 +1068,8 @@ static inline int ip6_ufo_append_data(struct sock *sk, int getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb), void *from, int length, int hh_len, int fragheaderlen, - int transhdrlen, int mtu,unsigned int flags) + int transhdrlen, int mtu,unsigned int flags, + struct rt6_info *rt) { struct sk_buff *skb; @@ -1084,7 +1114,7 @@ static inline int ip6_ufo_append_data(struct sock *sk, skb_shinfo(skb)->gso_size = (mtu - fragheaderlen - sizeof(struct frag_hdr)) & ~7; skb_shinfo(skb)->gso_type = SKB_GSO_UDP; - ipv6_select_ident(&fhdr); + ipv6_select_ident(&fhdr, rt); skb_shinfo(skb)->ip6_frag_id = fhdr.identification; __skb_queue_tail(&sk->sk_write_queue, skb); @@ -1233,7 +1263,7 @@ int ip6_append_data(struct sock *sk, int getfrag(void *from, char *to, err = ip6_ufo_append_data(sk, getfrag, from, length, hh_len, fragheaderlen, transhdrlen, mtu, - flags); + flags, rt); if (err) goto error; return 0; diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 154dd6b..f5ff5d3 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -1167,7 +1167,7 @@ static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb, int features) fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen); fptr->nexthdr = nexthdr; fptr->reserved = 0; - ipv6_select_ident(fptr); + ipv6_select_ident(fptr, (struct rt6_info *)skb_dst(skb)); /* Fragment the skb. ipv6 header and the remaining fields of the * fragment header are updated in ipv6_gso_segment() -- 1.7.5.4 -- Ben Hutchings Beware of programmers who carry screwdrivers. - Leonard Brandwein
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