From e8e36984080b55ac5e57bdb09a5b570f2fc8e963 Mon Sep 17 00:00:00 2001 From: Andrey Ignatov Date: Fri, 4 Jan 2019 01:07:07 -0800 Subject: [PATCH 1/2] bpf: Fix [::] -> [::1] rewrite in sys_sendmsg 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 Signed-off-by: Andrey Ignatov Signed-off-by: Alexei Starovoitov --- net/ipv6/udp.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 9cbf363172bd..7c3505006f8e 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -1390,10 +1390,7 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) 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; @@ -1421,6 +1418,9 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) } } + 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 = false; From 976b4f3a4646fbf0d189caca25f91f82e4be4b5a Mon Sep 17 00:00:00 2001 From: Andrey Ignatov Date: Fri, 4 Jan 2019 01:07:08 -0800 Subject: [PATCH 2/2] selftests/bpf: Test [::] -> [::1] rewrite in sys_sendmsg in test_sock_addr Test that sys_sendmsg BPF hook doesn't break sys_sendmsg behaviour to rewrite destination IPv6 = [::] with [::1] (BSD'ism). Two test cases are added: 1) User passes dst IPv6 = [::] and BPF_CGROUP_UDP6_SENDMSG program doesn't touch it. 2) User passes dst IPv6 != [::], but BPF_CGROUP_UDP6_SENDMSG program rewrites it with [::]. In both cases [::1] is used by sys_sendmsg code eventually and datagram is sent successfully for unconnected UDP socket. Example of relevant output: Test case: sendmsg6: set dst IP = [::] (BSD'ism) .. [PASS] Test case: sendmsg6: preserve dst IP = [::] (BSD'ism) .. [PASS] Signed-off-by: Andrey Ignatov Signed-off-by: Alexei Starovoitov --- tools/testing/selftests/bpf/test_sock_addr.c | 53 ++++++++++++++++++-- 1 file changed, 50 insertions(+), 3 deletions(-) diff --git a/tools/testing/selftests/bpf/test_sock_addr.c b/tools/testing/selftests/bpf/test_sock_addr.c index 73b7493d4120..d94336cbd8bd 100644 --- a/tools/testing/selftests/bpf/test_sock_addr.c +++ b/tools/testing/selftests/bpf/test_sock_addr.c @@ -44,6 +44,7 @@ #define SERV6_V4MAPPED_IP "::ffff:192.168.0.4" #define SRC6_IP "::1" #define SRC6_REWRITE_IP "::6" +#define WILDCARD6_IP "::" #define SERV6_PORT 6060 #define SERV6_REWRITE_PORT 6666 @@ -85,12 +86,14 @@ static int bind4_prog_load(const struct sock_addr_test *test); static int bind6_prog_load(const struct sock_addr_test *test); static int connect4_prog_load(const struct sock_addr_test *test); static int connect6_prog_load(const struct sock_addr_test *test); +static int sendmsg_allow_prog_load(const struct sock_addr_test *test); static int sendmsg_deny_prog_load(const struct sock_addr_test *test); static int sendmsg4_rw_asm_prog_load(const struct sock_addr_test *test); static int sendmsg4_rw_c_prog_load(const struct sock_addr_test *test); static int sendmsg6_rw_asm_prog_load(const struct sock_addr_test *test); static int sendmsg6_rw_c_prog_load(const struct sock_addr_test *test); static int sendmsg6_rw_v4mapped_prog_load(const struct sock_addr_test *test); +static int sendmsg6_rw_wildcard_prog_load(const struct sock_addr_test *test); static struct sock_addr_test tests[] = { /* bind */ @@ -462,6 +465,34 @@ static struct sock_addr_test tests[] = { SRC6_REWRITE_IP, SYSCALL_ENOTSUPP, }, + { + "sendmsg6: set dst IP = [::] (BSD'ism)", + sendmsg6_rw_wildcard_prog_load, + BPF_CGROUP_UDP6_SENDMSG, + BPF_CGROUP_UDP6_SENDMSG, + AF_INET6, + SOCK_DGRAM, + SERV6_IP, + SERV6_PORT, + SERV6_REWRITE_IP, + SERV6_REWRITE_PORT, + SRC6_REWRITE_IP, + SUCCESS, + }, + { + "sendmsg6: preserve dst IP = [::] (BSD'ism)", + sendmsg_allow_prog_load, + BPF_CGROUP_UDP6_SENDMSG, + BPF_CGROUP_UDP6_SENDMSG, + AF_INET6, + SOCK_DGRAM, + WILDCARD6_IP, + SERV6_PORT, + SERV6_REWRITE_IP, + SERV6_PORT, + SRC6_IP, + SUCCESS, + }, { "sendmsg6: deny call", sendmsg_deny_prog_load, @@ -734,16 +765,27 @@ static int connect6_prog_load(const struct sock_addr_test *test) return load_path(test, CONNECT6_PROG_PATH); } -static int sendmsg_deny_prog_load(const struct sock_addr_test *test) +static int sendmsg_ret_only_prog_load(const struct sock_addr_test *test, + int32_t rc) { struct bpf_insn insns[] = { - /* return 0 */ - BPF_MOV64_IMM(BPF_REG_0, 0), + /* return rc */ + BPF_MOV64_IMM(BPF_REG_0, rc), BPF_EXIT_INSN(), }; return load_insns(test, insns, sizeof(insns) / sizeof(struct bpf_insn)); } +static int sendmsg_allow_prog_load(const struct sock_addr_test *test) +{ + return sendmsg_ret_only_prog_load(test, /*rc*/ 1); +} + +static int sendmsg_deny_prog_load(const struct sock_addr_test *test) +{ + return sendmsg_ret_only_prog_load(test, /*rc*/ 0); +} + static int sendmsg4_rw_asm_prog_load(const struct sock_addr_test *test) { struct sockaddr_in dst4_rw_addr; @@ -864,6 +906,11 @@ static int sendmsg6_rw_v4mapped_prog_load(const struct sock_addr_test *test) return sendmsg6_rw_dst_asm_prog_load(test, SERV6_V4MAPPED_IP); } +static int sendmsg6_rw_wildcard_prog_load(const struct sock_addr_test *test) +{ + return sendmsg6_rw_dst_asm_prog_load(test, WILDCARD6_IP); +} + static int sendmsg6_rw_c_prog_load(const struct sock_addr_test *test) { return load_path(test, SENDMSG6_PROG_PATH);