Add raw tracepoint writable coverage for buffer accesses involving negative constant pointer adjustments.
The verifier case checks that a negative effective offset is rejected. The attach-time case adds incremental coverage beyond the existing nbd test and the verifier rejection case: it uses a negative var_off and a positive instruction offset whose effective offset remains non-negative. This exercises the checked access_end accounting path and verifies that the resulting max_tp_access is still checked against nbd_send_request's writable size at attach time. Signed-off-by: Sun Jian <[email protected]> --- .../raw_tp_writable_reject_nbd_invalid.c | 58 +++++++++++-------- .../bpf/progs/verifier_raw_tp_writable.c | 16 +++++ 2 files changed, 51 insertions(+), 23 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/raw_tp_writable_reject_nbd_invalid.c b/tools/testing/selftests/bpf/prog_tests/raw_tp_writable_reject_nbd_invalid.c index 216b0dfac0fe..efe4cad47b28 100644 --- a/tools/testing/selftests/bpf/prog_tests/raw_tp_writable_reject_nbd_invalid.c +++ b/tools/testing/selftests/bpf/prog_tests/raw_tp_writable_reject_nbd_invalid.c @@ -4,12 +4,31 @@ #include <linux/nbd.h> #include "bpf_util.h" -void test_raw_tp_writable_reject_nbd_invalid(void) +static void check_nbd_attach_reject(const char *name, + const struct bpf_insn *program, size_t prog_len) { - __u32 duration = 0; + LIBBPF_OPTS(bpf_prog_load_opts, opts); char error[4096]; - int bpf_fd = -1, tp_fd = -1; + int bpf_fd, tp_fd; + + opts.log_level = 2; + opts.log_buf = error; + opts.log_size = sizeof(error); + + bpf_fd = bpf_prog_load(BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE, NULL, "GPL v2", + program, prog_len, &opts); + if (!ASSERT_GE(bpf_fd, 0, "prog_load")) + return; + + tp_fd = bpf_raw_tracepoint_open("nbd_send_request", bpf_fd); + if (!ASSERT_LT(tp_fd, 0, name)) + close(tp_fd); + + close(bpf_fd); +} +void test_raw_tp_writable_reject_nbd_invalid(void) +{ const struct bpf_insn program[] = { /* r6 is our tp buffer */ BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, 0), @@ -19,25 +38,18 @@ void test_raw_tp_writable_reject_nbd_invalid(void) BPF_EXIT_INSN(), }; - LIBBPF_OPTS(bpf_prog_load_opts, opts, - .log_level = 2, - .log_buf = error, - .log_size = sizeof(error), - ); - - bpf_fd = bpf_prog_load(BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE, NULL, "GPL v2", - program, ARRAY_SIZE(program), - &opts); - if (CHECK(bpf_fd < 0, "bpf_raw_tracepoint_writable load", - "failed: %d errno %d\n", bpf_fd, errno)) - return; - - tp_fd = bpf_raw_tracepoint_open("nbd_send_request", bpf_fd); - if (CHECK(tp_fd >= 0, "bpf_raw_tracepoint_writable open", - "erroneously succeeded\n")) - goto out_bpffd; + const struct bpf_insn negative_var_off_program[] = { + BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, 0), + /* make var_off negative, but keep the effective access offset non-negative */ + BPF_ALU64_IMM(BPF_ADD, BPF_REG_6, -8), + /* one byte beyond the end of the nbd_request struct */ + BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_6, + sizeof(struct nbd_request) + 8), + BPF_EXIT_INSN(), + }; - close(tp_fd); -out_bpffd: - close(bpf_fd); + check_nbd_attach_reject("nbd_invalid", program, ARRAY_SIZE(program)); + check_nbd_attach_reject("nbd_invalid_negative_var_off", + negative_var_off_program, + ARRAY_SIZE(negative_var_off_program)); } diff --git a/tools/testing/selftests/bpf/progs/verifier_raw_tp_writable.c b/tools/testing/selftests/bpf/progs/verifier_raw_tp_writable.c index 14a0172e2141..4055a6443bc2 100644 --- a/tools/testing/selftests/bpf/progs/verifier_raw_tp_writable.c +++ b/tools/testing/selftests/bpf/progs/verifier_raw_tp_writable.c @@ -47,4 +47,20 @@ l0_%=: /* shift the buffer pointer to a variable location */\ : __clobber_all); } +SEC("raw_tracepoint.w") +__description("raw_tracepoint_writable: reject negative const offset") +__failure +__msg("invalid negative tracepoint buffer offset") +__naked void tracepoint_writable_reject_negative_const_offset(void) +{ + asm volatile (" \ + r6 = *(u64 *)(r1 + 0); \ + r6 += -8; \ + r0 = *(u64 *)(r6 + 0); \ + exit; \ +" : + : + : __clobber_all); +} + char _license[] SEC("license") = "GPL"; -- 2.43.0
