From 9eeb3aa33ae005526f672b394c1791578463513f Mon Sep 17 00:00:00 2001 From: Hengqi Chen Date: Thu, 21 Oct 2021 21:47:51 +0800 Subject: [PATCH 1/2] bpf: Add bpf_skc_to_unix_sock() helper The helper is used in tracing programs to cast a socket pointer to a unix_sock pointer. The return value could be NULL if the casting is illegal. Suggested-by: Yonghong Song Signed-off-by: Hengqi Chen Signed-off-by: Alexei Starovoitov Acked-by: Song Liu Link: https://lore.kernel.org/bpf/20211021134752.1223426-2-hengqi.chen@gmail.com --- include/linux/bpf.h | 1 + include/uapi/linux/bpf.h | 7 +++++++ kernel/trace/bpf_trace.c | 2 ++ net/core/filter.c | 23 +++++++++++++++++++++++ scripts/bpf_doc.py | 2 ++ tools/include/uapi/linux/bpf.h | 7 +++++++ 6 files changed, 42 insertions(+) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index d604c8251d88..be3102b4554b 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -2093,6 +2093,7 @@ extern const struct bpf_func_proto bpf_skc_to_tcp_sock_proto; extern const struct bpf_func_proto bpf_skc_to_tcp_timewait_sock_proto; extern const struct bpf_func_proto bpf_skc_to_tcp_request_sock_proto; extern const struct bpf_func_proto bpf_skc_to_udp6_sock_proto; +extern const struct bpf_func_proto bpf_skc_to_unix_sock_proto; extern const struct bpf_func_proto bpf_copy_from_user_proto; extern const struct bpf_func_proto bpf_snprintf_btf_proto; extern const struct bpf_func_proto bpf_snprintf_proto; diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 6fc59d61937a..22e7a3f38b9f 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -4909,6 +4909,12 @@ union bpf_attr { * Return * The number of bytes written to the buffer, or a negative error * in case of failure. + * + * struct unix_sock *bpf_skc_to_unix_sock(void *sk) + * Description + * Dynamically cast a *sk* pointer to a *unix_sock* pointer. + * Return + * *sk* if casting is valid, or **NULL** otherwise. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -5089,6 +5095,7 @@ union bpf_attr { FN(task_pt_regs), \ FN(get_branch_snapshot), \ FN(trace_vprintk), \ + FN(skc_to_unix_sock), \ /* */ /* integer value in 'imm' field of BPF_CALL instruction selects which helper diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 6b3153841a33..cbcd0d6fca7c 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -1608,6 +1608,8 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_skc_to_tcp_request_sock_proto; case BPF_FUNC_skc_to_udp6_sock: return &bpf_skc_to_udp6_sock_proto; + case BPF_FUNC_skc_to_unix_sock: + return &bpf_skc_to_unix_sock_proto; case BPF_FUNC_sk_storage_get: return &bpf_sk_storage_get_tracing_proto; case BPF_FUNC_sk_storage_delete: diff --git a/net/core/filter.c b/net/core/filter.c index 4bace37a6a44..8e8d3b49c297 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -10723,6 +10723,26 @@ const struct bpf_func_proto bpf_skc_to_udp6_sock_proto = { .ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_UDP6], }; +BPF_CALL_1(bpf_skc_to_unix_sock, struct sock *, sk) +{ + /* unix_sock type is not generated in dwarf and hence btf, + * trigger an explicit type generation here. + */ + BTF_TYPE_EMIT(struct unix_sock); + if (sk && sk_fullsock(sk) && sk->sk_family == AF_UNIX) + return (unsigned long)sk; + + return (unsigned long)NULL; +} + +const struct bpf_func_proto bpf_skc_to_unix_sock_proto = { + .func = bpf_skc_to_unix_sock, + .gpl_only = false, + .ret_type = RET_PTR_TO_BTF_ID_OR_NULL, + .arg1_type = ARG_PTR_TO_BTF_ID_SOCK_COMMON, + .ret_btf_id = &btf_sock_ids[BTF_SOCK_TYPE_UNIX], +}; + BPF_CALL_1(bpf_sock_from_file, struct file *, file) { return (unsigned long)sock_from_file(file); @@ -10762,6 +10782,9 @@ bpf_sk_base_func_proto(enum bpf_func_id func_id) case BPF_FUNC_skc_to_udp6_sock: func = &bpf_skc_to_udp6_sock_proto; break; + case BPF_FUNC_skc_to_unix_sock: + func = &bpf_skc_to_unix_sock_proto; + break; default: return bpf_base_func_proto(func_id); } diff --git a/scripts/bpf_doc.py b/scripts/bpf_doc.py index 00ac7b79cddb..a6403ddf5de7 100755 --- a/scripts/bpf_doc.py +++ b/scripts/bpf_doc.py @@ -537,6 +537,7 @@ class PrinterHelpers(Printer): 'struct tcp_timewait_sock', 'struct tcp_request_sock', 'struct udp6_sock', + 'struct unix_sock', 'struct task_struct', 'struct __sk_buff', @@ -589,6 +590,7 @@ class PrinterHelpers(Printer): 'struct tcp_timewait_sock', 'struct tcp_request_sock', 'struct udp6_sock', + 'struct unix_sock', 'struct task_struct', 'struct path', 'struct btf_ptr', diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 6fc59d61937a..22e7a3f38b9f 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -4909,6 +4909,12 @@ union bpf_attr { * Return * The number of bytes written to the buffer, or a negative error * in case of failure. + * + * struct unix_sock *bpf_skc_to_unix_sock(void *sk) + * Description + * Dynamically cast a *sk* pointer to a *unix_sock* pointer. + * Return + * *sk* if casting is valid, or **NULL** otherwise. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -5089,6 +5095,7 @@ union bpf_attr { FN(task_pt_regs), \ FN(get_branch_snapshot), \ FN(trace_vprintk), \ + FN(skc_to_unix_sock), \ /* */ /* integer value in 'imm' field of BPF_CALL instruction selects which helper From b6c4e71516099be676ebd897ea440ce2dddca6d1 Mon Sep 17 00:00:00 2001 From: Hengqi Chen Date: Thu, 21 Oct 2021 21:47:52 +0800 Subject: [PATCH 2/2] selftests/bpf: Test bpf_skc_to_unix_sock() helper Add a new test which triggers unix_listen kernel function to test bpf_skc_to_unix_sock helper. Signed-off-by: Hengqi Chen Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20211021134752.1223426-3-hengqi.chen@gmail.com --- .../bpf/prog_tests/skc_to_unix_sock.c | 54 +++++++++++++++++++ .../bpf/progs/test_skc_to_unix_sock.c | 40 ++++++++++++++ 2 files changed, 94 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/skc_to_unix_sock.c create mode 100644 tools/testing/selftests/bpf/progs/test_skc_to_unix_sock.c diff --git a/tools/testing/selftests/bpf/prog_tests/skc_to_unix_sock.c b/tools/testing/selftests/bpf/prog_tests/skc_to_unix_sock.c new file mode 100644 index 000000000000..3eefdfed1db9 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/skc_to_unix_sock.c @@ -0,0 +1,54 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* Copyright (c) 2021 Hengqi Chen */ + +#include +#include +#include "test_skc_to_unix_sock.skel.h" + +static const char *sock_path = "@skc_to_unix_sock"; + +void test_skc_to_unix_sock(void) +{ + struct test_skc_to_unix_sock *skel; + struct sockaddr_un sockaddr; + int err, sockfd = 0; + + skel = test_skc_to_unix_sock__open(); + if (!ASSERT_OK_PTR(skel, "could not open BPF object")) + return; + + skel->rodata->my_pid = getpid(); + + err = test_skc_to_unix_sock__load(skel); + if (!ASSERT_OK(err, "could not load BPF object")) + goto cleanup; + + err = test_skc_to_unix_sock__attach(skel); + if (!ASSERT_OK(err, "could not attach BPF object")) + goto cleanup; + + /* trigger unix_listen */ + sockfd = socket(AF_UNIX, SOCK_STREAM, 0); + if (!ASSERT_GT(sockfd, 0, "socket failed")) + goto cleanup; + + memset(&sockaddr, 0, sizeof(sockaddr)); + sockaddr.sun_family = AF_UNIX; + strncpy(sockaddr.sun_path, sock_path, strlen(sock_path)); + sockaddr.sun_path[0] = '\0'; + + err = bind(sockfd, (struct sockaddr *)&sockaddr, sizeof(sockaddr)); + if (!ASSERT_OK(err, "bind failed")) + goto cleanup; + + err = listen(sockfd, 1); + if (!ASSERT_OK(err, "listen failed")) + goto cleanup; + + ASSERT_EQ(strcmp(skel->bss->path, sock_path), 0, "bpf_skc_to_unix_sock failed"); + +cleanup: + if (sockfd) + close(sockfd); + test_skc_to_unix_sock__destroy(skel); +} diff --git a/tools/testing/selftests/bpf/progs/test_skc_to_unix_sock.c b/tools/testing/selftests/bpf/progs/test_skc_to_unix_sock.c new file mode 100644 index 000000000000..a408ec95cba4 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_skc_to_unix_sock.c @@ -0,0 +1,40 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* Copyright (c) 2021 Hengqi Chen */ + +#include "vmlinux.h" +#include +#include +#include "bpf_tracing_net.h" + +const volatile pid_t my_pid = 0; +char path[256] = {}; + +SEC("fentry/unix_listen") +int BPF_PROG(unix_listen, struct socket *sock, int backlog) +{ + pid_t pid = bpf_get_current_pid_tgid() >> 32; + struct unix_sock *unix_sk; + int i, len; + + if (pid != my_pid) + return 0; + + unix_sk = (struct unix_sock *)bpf_skc_to_unix_sock(sock->sk); + if (!unix_sk) + return 0; + + if (!UNIX_ABSTRACT(unix_sk)) + return 0; + + len = unix_sk->addr->len - sizeof(short); + path[0] = '@'; + for (i = 1; i < len; i++) { + if (i >= sizeof(struct sockaddr_un)) + break; + + path[i] = unix_sk->addr->name->sun_path[i]; + } + return 0; +} + +char _license[] SEC("license") = "GPL";