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authorLudovic Cintrat <ludovic.cintrat@gatewatcher.com>2022-09-07 13:08:13 +0300
committerDavid S. Miller <davem@davemloft.net>2022-09-09 14:48:00 +0300
commit64ae13ed478428135cddc2f1113dff162d8112d4 (patch)
tree04e4d5a443fc7a2dc3cd5a928cfbb8d9e67150b7 /net/core
parent81225b2ea161af48e093f58e8dfee6d705b16af4 (diff)
downloadlinux-64ae13ed478428135cddc2f1113dff162d8112d4.tar.xz
net: core: fix flow symmetric hash
__flow_hash_consistentify() wrongly swaps ipv4 addresses in few cases. This function is indirectly used by __skb_get_hash_symmetric(), which is used to fanout packets in AF_PACKET. Intrusion detection systems may be impacted by this issue. __flow_hash_consistentify() computes the addresses difference then swaps them if the difference is negative. In few cases src - dst and dst - src are both negative. The following snippet mimics __flow_hash_consistentify(): ``` #include <stdio.h> #include <stdint.h> int main(int argc, char** argv) { int diffs_d, diffd_s; uint32_t dst = 0xb225a8c0; /* 178.37.168.192 --> 192.168.37.178 */ uint32_t src = 0x3225a8c0; /* 50.37.168.192 --> 192.168.37.50 */ uint32_t dst2 = 0x3325a8c0; /* 51.37.168.192 --> 192.168.37.51 */ diffs_d = src - dst; diffd_s = dst - src; printf("src:%08x dst:%08x, diff(s-d)=%d(0x%x) diff(d-s)=%d(0x%x)\n", src, dst, diffs_d, diffs_d, diffd_s, diffd_s); diffs_d = src - dst2; diffd_s = dst2 - src; printf("src:%08x dst:%08x, diff(s-d)=%d(0x%x) diff(d-s)=%d(0x%x)\n", src, dst2, diffs_d, diffs_d, diffd_s, diffd_s); return 0; } ``` Results: src:3225a8c0 dst:b225a8c0, \ diff(s-d)=-2147483648(0x80000000) \ diff(d-s)=-2147483648(0x80000000) src:3225a8c0 dst:3325a8c0, \ diff(s-d)=-16777216(0xff000000) \ diff(d-s)=16777216(0x1000000) In the first case the addresses differences are always < 0, therefore __flow_hash_consistentify() always swaps, thus dst->src and src->dst packets have differents hashes. Fixes: c3f8324188fa8 ("net: Add full IPv6 addresses to flow_keys") Signed-off-by: Ludovic Cintrat <ludovic.cintrat@gatewatcher.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
-rw-r--r--net/core/flow_dissector.c5
1 files changed, 2 insertions, 3 deletions
diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 764c4cb3fe8f..5dc3860e9fc7 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -1611,9 +1611,8 @@ static inline void __flow_hash_consistentify(struct flow_keys *keys)
switch (keys->control.addr_type) {
case FLOW_DISSECTOR_KEY_IPV4_ADDRS:
- addr_diff = (__force u32)keys->addrs.v4addrs.dst -
- (__force u32)keys->addrs.v4addrs.src;
- if (addr_diff < 0)
+ if ((__force u32)keys->addrs.v4addrs.dst <
+ (__force u32)keys->addrs.v4addrs.src)
swap(keys->addrs.v4addrs.src, keys->addrs.v4addrs.dst);
if ((__force u16)keys->ports.dst <