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| author | Eric Dumazet <edumazet@google.com> | 2026-08-18 15:12:13 +0000 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-08-20 12:55:31 -0700 |
| commit | 2ee66e9487172fcd189bc52a767c30dad7141c09 (patch) | |
| tree | 13f1220706642f90c3d0039770ce66fbd6084da6 /include | |
| parent | 235b42b5860189eb8c27c36435ad932cae65a734 (diff) | |
| download | linux-stable-2ee66e9487172fcd189bc52a767c30dad7141c09.tar.gz linux-stable-2ee66e9487172fcd189bc52a767c30dad7141c09.zip | |
inetpeer: randomize RB-tree node comparison using SipHash
The inetpeer rate limiting system stores peer entries in a Red-Black tree
keyed deterministically on the remote IP address. Because tree lookups walk
the RB-tree using standard lexicographical comparisons (inetpeer_addr_cmp),
an off-path adversary can predict the exact topology of the tree and the
sequence of nodes traversed during lookups (the gc_stack candidate list).
By combining deterministic tree traversal with aggressive garbage collection
(triggered when tree size exceeds inet_peer_threshold), an attacker can
selectively force the eviction of targeted inet_peer nodes. When an evicted
node is subsequently re-created upon receiving a new packet, its rate-limiting
token bucket (rate_tokens, rate_last) is reset to full capacity. This creates
a side-channel primitive allowing off-path attackers to bypass IP-keyed ICMP
rate limits and infer open UDP ports (similar to SAD DNS style attacks).
Mitigate this by randomizing the RB-tree node comparison logic using SipHash
with a secret key (inetpeer_hash_key) initialized via net_get_random_once().
Nodes are ordered in the tree by SipHash(addr, key) rather than raw IP
addresses. Because the secret key is unknown to external entities, the tree
layout and lookup traversal paths are unpredictable to off-path adversaries,
breaking the deterministic eviction gadget.
Cache the computed 64-bit SipHash (hash) in struct inet_peer and compute the
target hash (dhash) once at the beginning of inet_getpeer() to avoid recomputing
SipHash at every step of the RB-tree walk.
Fixes: b145425f269a ("inetpeer: remove AVL implementation in favor of RB tree")
Reported-by: Michael Blunt <michaelbblunt@gmail.com>
Suggested-by: Michael Blunt <michaelbblunt@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260818151213.3953963-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/net/inetpeer.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/include/net/inetpeer.h b/include/net/inetpeer.h index f475757daafb..414e9adf4c51 100644 --- a/include/net/inetpeer.h +++ b/include/net/inetpeer.h @@ -35,6 +35,7 @@ struct inetpeer_addr { struct inet_peer { struct rb_node rb_node; + u64 hash; struct inetpeer_addr daddr; u32 metrics[RTAX_MAX]; @@ -125,6 +126,9 @@ static inline int inetpeer_addr_cmp(const struct inetpeer_addr *a, { int i, n; + if (a->family != b->family) + return a->family < b->family ? -1 : 1; + if (a->family == AF_INET) n = sizeof(a->a4) / sizeof(u32); else |