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ipv4: restrict IPOPT_SSRR and IPOPT_LSRR options

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This patch restricts setting Loose Source and Record Route (LSRR)
and Strict Source and Record Route (SSRR) IP options to users
with CAP_NET_RAW capability.

This prevents unprivileged applications from forcing packets to route
through attacker-controlled nodes to leak TCP ISN and possibly other
protocol information.

While LSRR and SSRR are commonly filtered in many network environments,
they may still be supported and forwarded along some network paths.

RFC 7126 (Recommendations on Filtering of IPv4 Packets Containing
IPv4 Options) recommend to drop these options in 4.3 and 4.4.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Reported-by: Tamir Shahar <tamirthesis@gmail.com>
Reported-by: Amit Klein <aksecurity@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20260602161547.2642155-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2026-06-02 16:15:47 +00:00 committed by Jakub Kicinski
parent c8e14cc9cc
commit d3915a1f5a
1 changed files with 4 additions and 0 deletions
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4
net/ipv4/ip_options.c
View File

@ -530,6 +530,10 @@ int ip_options_get(struct net *net, struct ip_options_rcu **optp,
kfree(opt);
return -EINVAL;
}
if (opt->opt.srr && !ns_capable(net->user_ns, CAP_NET_RAW)) {
kfree(opt);
return -EPERM;
}
kfree(*optp);
*optp = opt;
return 0;