Add a selftest that verifies SOCK_OPS_GET_SK() correctly returns NULL when dst_reg == src_reg and is_fullsock == 0.
The BPF program reads ctx->is_fullsock, then loads ctx->sk using the same register for source and destination. When is_fullsock == 0, sk must be NULL. The test triggers this path via a TCP handshake (which causes TCP_NEW_SYN_RECV state) and checks: - null_seen == 1: the is_fullsock==0 path was hit with correct NULL sk - bug_detected == 0: sk was never non-NULL when is_fullsock==0 Signed-off-by: Jiayuan Chen <[email protected]> --- .../bpf/prog_tests/sock_ops_get_sk.c | 62 +++++++++++++++++++ .../selftests/bpf/progs/sock_ops_get_sk.c | 44 +++++++++++++ 2 files changed, 106 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/sock_ops_get_sk.c create mode 100644 tools/testing/selftests/bpf/progs/sock_ops_get_sk.c diff --git a/tools/testing/selftests/bpf/prog_tests/sock_ops_get_sk.c b/tools/testing/selftests/bpf/prog_tests/sock_ops_get_sk.c new file mode 100644 index 0000000000000..9eaf97786c1d9 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/sock_ops_get_sk.c @@ -0,0 +1,62 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <test_progs.h> +#include "cgroup_helpers.h" +#include "network_helpers.h" +#include "sock_ops_get_sk.skel.h" + +/* + * Test that reading ctx->sk with dst_reg == src_reg in a sock_ops program + * correctly returns NULL when is_fullsock == 0 (TCP_NEW_SYN_RECV state). + * + * The bug was in SOCK_OPS_GET_SK() macro which failed to zero the destination + * register when it was the same as the source register and the socket was not + * a full socket. This left the ctx pointer in the register, which then passed + * the NULL check and could be used as a socket pointer, causing OOB access. + */ +void test_sock_ops_get_sk(void) +{ + struct sock_ops_get_sk *skel; + int cgroup_fd, server_fd, client_fd; + int prog_fd, err; + + cgroup_fd = test__join_cgroup("/sock_ops_get_sk"); + if (!ASSERT_GE(cgroup_fd, 0, "join_cgroup")) + return; + + skel = sock_ops_get_sk__open_and_load(); + if (!ASSERT_OK_PTR(skel, "skel_open_load")) + goto close_cgroup; + + prog_fd = bpf_program__fd(skel->progs.sock_ops_get_sk_same_reg); + err = bpf_prog_attach(prog_fd, cgroup_fd, BPF_CGROUP_SOCK_OPS, 0); + if (!ASSERT_OK(err, "prog_attach")) + goto destroy_skel; + + server_fd = start_server(AF_INET, SOCK_STREAM, NULL, 0, 0); + if (!ASSERT_GE(server_fd, 0, "start_server")) + goto detach; + + /* Trigger TCP handshake which causes TCP_NEW_SYN_RECV state where + * is_fullsock == 0. With the bug, ctx->sk loaded with same src/dst + * register would return a stale ctx pointer instead of NULL. + */ + client_fd = connect_to_fd(server_fd, 0); + if (!ASSERT_GE(client_fd, 0, "connect_to_fd")) + goto close_server; + + close(client_fd); + + /* Verify that the is_fullsock == 0 path was hit and sk was NULL */ + ASSERT_EQ(skel->bss->null_seen, 1, "null_seen"); + ASSERT_EQ(skel->bss->bug_detected, 0, "bug_not_detected"); + +close_server: + close(server_fd); +detach: + bpf_prog_detach(cgroup_fd, BPF_CGROUP_SOCK_OPS); +destroy_skel: + sock_ops_get_sk__destroy(skel); +close_cgroup: + close(cgroup_fd); +} diff --git a/tools/testing/selftests/bpf/progs/sock_ops_get_sk.c b/tools/testing/selftests/bpf/progs/sock_ops_get_sk.c new file mode 100644 index 0000000000000..4a75614b21eb5 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/sock_ops_get_sk.c @@ -0,0 +1,44 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include "vmlinux.h" +#include <bpf/bpf_helpers.h> +#include "bpf_misc.h" + +/* + * Test that SOCK_OPS_GET_SK() correctly returns NULL when dst_reg == src_reg + * and is_fullsock == 0 (e.g., during TCP_NEW_SYN_RECV). Before the fix, the + * macro failed to zero the destination register, leaving a stale ctx pointer + * that bypassed the NULL check. + */ + +int bug_detected; +int null_seen; + +SEC("sockops") +__naked void sock_ops_get_sk_same_reg(void) +{ + asm volatile ( + "r7 = *(u32 *)(r1 + %[is_fullsock_off]);" + "r1 = *(u64 *)(r1 + %[sk_off]);" + "if r7 != 0 goto 2f;" + "if r1 == 0 goto 1f;" + "r1 = %[bug_detected] ll;" + "r2 = 1;" + "*(u32 *)(r1 + 0) = r2;" + "goto 2f;" + "1:" + "r1 = %[null_seen] ll;" + "r2 = 1;" + "*(u32 *)(r1 + 0) = r2;" + "2:" + "r0 = 1;" + "exit;" + : + : __imm_const(is_fullsock_off, offsetof(struct bpf_sock_ops, is_fullsock)), + __imm_const(sk_off, offsetof(struct bpf_sock_ops, sk)), + __imm_addr(bug_detected), + __imm_addr(null_seen) + : __clobber_all); +} + +char _license[] SEC("license") = "GPL"; -- 2.43.0
