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| author | Ludovic Cintrat <ludovic.cintrat@gatewatcher.com> | 2022-09-07 12:08:13 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2022-09-09 12:48:00 +0100 |
| commit | 64ae13ed478428135cddc2f1113dff162d8112d4 (patch) | |
| tree | 04e4d5a443fc7a2dc3cd5a928cfbb8d9e67150b7 /net | |
| parent | 81225b2ea161af48e093f58e8dfee6d705b16af4 (diff) | |
| download | linux-64ae13ed478428135cddc2f1113dff162d8112d4.tar.bz2 | |
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')
| -rw-r--r-- | net/core/flow_dissector.c | 5 |
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 < |