From: Andrey Ignatov <rdna@fb.com>
Date: Fri, 4 Jan 2019 01:07:07 -0800
Subject: bpf: Fix [::] -> [::1] rewrite in sys_sendmsg
Patch-mainline: v5.0-rc3
Git-commit: e8e36984080b55ac5e57bdb09a5b570f2fc8e963
References: bsc#1109837
sys_sendmsg has supported unspecified destination IPv6 (wildcard) for
unconnected UDP sockets since 876c7f41. When [::] is passed by user as
destination, sys_sendmsg rewrites it with [::1] to be consistent with
BSD (see "BSD'ism" comment in the code).
This didn't work when cgroup-bpf was enabled though since the rewrite
[::] -> [::1] happened before passing control to cgroup-bpf block where
fl6.daddr was updated with passed by user sockaddr_in6.sin6_addr (that
might or might not be changed by BPF program). That way if user passed
[::] as dst IPv6 it was first rewritten with [::1] by original code from
876c7f41, but then rewritten back with [::] by cgroup-bpf block.
It happened even when BPF_CGROUP_UDP6_SENDMSG program was not present
(CONFIG_CGROUP_BPF=y was enough).
The fix is to apply BSD'ism after cgroup-bpf block so that [::] is
replaced with [::1] no matter where it came from: passed by user to
sys_sendmsg or set by BPF_CGROUP_UDP6_SENDMSG program.
Fixes: 1cedee13d25a ("bpf: Hooks for sys_sendmsg")
Reported-by: Nitin Rawat <nitin.rawat@intel.com>
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
net/ipv6/udp.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1301,10 +1301,7 @@ do_udp_sendmsg:
ipc6.opt = opt;
fl6.flowi6_proto = sk->sk_protocol;
- if (!ipv6_addr_any(daddr))
- fl6.daddr = *daddr;
- else
- fl6.daddr.s6_addr[15] = 0x1; /* :: means loopback (BSD'ism) */
+ fl6.daddr = *daddr;
if (ipv6_addr_any(&fl6.saddr) && !ipv6_addr_any(&np->saddr))
fl6.saddr = np->saddr;
fl6.fl6_sport = inet->inet_sport;
@@ -1332,6 +1329,9 @@ do_udp_sendmsg:
}
}
+ if (ipv6_addr_any(&fl6.daddr))
+ fl6.daddr.s6_addr[15] = 0x1; /* :: means loopback (BSD'ism) */
+
final_p = fl6_update_dst(&fl6, opt, &final);
if (final_p)
connected = 0;