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authorMenglong Dong <imagedong@tencent.com>2022-01-06 21:20:20 +0800
committerAlexei Starovoitov <ast@kernel.org>2022-01-06 17:08:35 -0800
commit91a760b26926265a60c77ddf016529bcf3e17a04 (patch)
treeae83cb44feeae886d3bebb102371980540bf376b /net/ipv6/udp.c
parent44bab87d8ca6f0544a9f8fc97bdf33aa5b3c899e (diff)
net: bpf: Handle return value of BPF_CGROUP_RUN_PROG_INET{4,6}_POST_BIND()
The return value of BPF_CGROUP_RUN_PROG_INET{4,6}_POST_BIND() in __inet_bind() is not handled properly. While the return value is non-zero, it will set inet_saddr and inet_rcv_saddr to 0 and exit: err = BPF_CGROUP_RUN_PROG_INET4_POST_BIND(sk); if (err) { inet->inet_saddr = inet->inet_rcv_saddr = 0; goto out_release_sock; } Let's take UDP for example and see what will happen. For UDP socket, it will be added to 'udp_prot.h.udp_table->hash' and 'udp_prot.h.udp_table->hash2' after the sk->sk_prot->get_port() called success. If 'inet->inet_rcv_saddr' is specified here, then 'sk' will be in the 'hslot2' of 'hash2' that it don't belong to (because inet_saddr is changed to 0), and UDP packet received will not be passed to this sock. If 'inet->inet_rcv_saddr' is not specified here, the sock will work fine, as it can receive packet properly, which is wired, as the 'bind()' is already failed. To undo the get_port() operation, introduce the 'put_port' field for 'struct proto'. For TCP proto, it is inet_put_port(); For UDP proto, it is udp_lib_unhash(); For icmp proto, it is ping_unhash(). Therefore, after sys_bind() fail caused by BPF_CGROUP_RUN_PROG_INET4_POST_BIND(), it will be unbinded, which means that it can try to be binded to another port. Signed-off-by: Menglong Dong <imagedong@tencent.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20220106132022.3470772-2-imagedong@tencent.com
Diffstat (limited to 'net/ipv6/udp.c')
-rw-r--r--net/ipv6/udp.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 1accc06abc54..90718a924ca8 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1732,6 +1732,7 @@ struct proto udpv6_prot = {
.unhash = udp_lib_unhash,
.rehash = udp_v6_rehash,
.get_port = udp_v6_get_port,
+ .put_port = udp_lib_unhash,
#ifdef CONFIG_BPF_SYSCALL
.psock_update_sk_prot = udp_bpf_update_proto,
#endif