From: Maciej Żenczykowski maze@google.com
[ Upstream commit a9628e88776eb7d045cf46467f1afdd0f7fe72ea ]
This reverts commit 1f86123b9749 ("net: align SO_RCVMARK required privileges with SO_MARK") because the reasoning in the commit message is not really correct: SO_RCVMARK is used for 'reading' incoming skb mark (via cmsg), as such it is more equivalent to 'getsockopt(SO_MARK)' which has no priv check and retrieves the socket mark, rather than 'setsockopt(SO_MARK) which sets the socket mark and does require privs.
Additionally incoming skb->mark may already be visible if sysctl_fwmark_reflect and/or sysctl_tcp_fwmark_accept are enabled.
Furthermore, it is easier to block the getsockopt via bpf (either cgroup setsockopt hook, or via syscall filters) then to unblock it if it requires CAP_NET_RAW/ADMIN.
On Android the socket mark is (among other things) used to store the network identifier a socket is bound to. Setting it is privileged, but retrieving it is not. We'd like unprivileged userspace to be able to read the network id of incoming packets (where mark is set via iptables [to be moved to bpf])...
An alternative would be to add another sysctl to control whether setting SO_RCVMARK is privilged or not. (or even a MASK of which bits in the mark can be exposed) But this seems like over-engineering...
Note: This is a non-trivial revert, due to later merged commit e42c7beee71d ("bpf: net: Consider has_current_bpf_ctx() when testing capable() in sk_setsockopt()") which changed both 'ns_capable' into 'sockopt_ns_capable' calls.
Fixes: 1f86123b9749 ("net: align SO_RCVMARK required privileges with SO_MARK") Cc: Larysa Zaremba larysa.zaremba@intel.com Cc: Simon Horman simon.horman@corigine.com Cc: Paolo Abeni pabeni@redhat.com Cc: Eyal Birger eyal.birger@gmail.com Cc: Jakub Kicinski kuba@kernel.org Cc: Eric Dumazet edumazet@google.com Cc: Patrick Rohr prohr@google.com Signed-off-by: Maciej Żenczykowski maze@google.com Reviewed-by: Simon Horman simon.horman@corigine.com Reviewed-by: Kuniyuki Iwashima kuniyu@amazon.com Link: https://lore.kernel.org/r/20230618103130.51628-1-maze@google.com Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/core/sock.c | 6 ------ 1 file changed, 6 deletions(-)
diff --git a/net/core/sock.c b/net/core/sock.c index 3fd71f343c9f2..b34c48f802e98 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1362,12 +1362,6 @@ int sk_setsockopt(struct sock *sk, int level, int optname, __sock_set_mark(sk, val); break; case SO_RCVMARK: - if (!sockopt_ns_capable(sock_net(sk)->user_ns, CAP_NET_RAW) && - !sockopt_ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN)) { - ret = -EPERM; - break; - } - sock_valbool_flag(sk, SOCK_RCVMARK, valbool); break;