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Date:   Mon, 22 Apr 2019 18:32:01 +0000
From:   Yonghong Song <yhs@...com>
To:     Matt Mullins <mmullins@...com>, Andrew Hall <hall@...com>,
        "ast@...nel.org" <ast@...nel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Steven Rostedt" <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        "Daniel Borkmann" <daniel@...earbox.net>,
        Martin Lau <kafai@...com>, Song Liu <songliubraving@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Shuah Khan <shuah@...nel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH bpf-next v3 5/5] selftests: bpf: test writable buffers in
 raw tps



On 4/19/19 2:04 PM, Matt Mullins wrote:
> This tests that:
>    * a BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE cannot be attached if it
>      uses either:
>      * a variable offset to the tracepoint buffer, or
>      * an offset beyond the size of the tracepoint buffer
>    * a tracer can modify the buffer provided when attached to a writable
>      tracepoint in bpf_prog_test_run
> 
> Signed-off-by: Matt Mullins <mmullins@...com>
> ---
>   include/trace/events/bpf_test_run.h           | 50 ++++++++++++
>   net/bpf/test_run.c                            |  4 +
>   .../raw_tp_writable_reject_nbd_invalid.c      | 40 ++++++++++
>   .../bpf/prog_tests/raw_tp_writable_test_run.c | 80 +++++++++++++++++++
>   .../selftests/bpf/verifier/raw_tp_writable.c  | 34 ++++++++
>   5 files changed, 208 insertions(+)
>   create mode 100644 include/trace/events/bpf_test_run.h
>   create mode 100644 tools/testing/selftests/bpf/prog_tests/raw_tp_writable_reject_nbd_invalid.c
>   create mode 100644 tools/testing/selftests/bpf/prog_tests/raw_tp_writable_test_run.c
>   create mode 100644 tools/testing/selftests/bpf/verifier/raw_tp_writable.c
> 
> diff --git a/include/trace/events/bpf_test_run.h b/include/trace/events/bpf_test_run.h
> new file mode 100644
> index 000000000000..abf466839ea4
> --- /dev/null
> +++ b/include/trace/events/bpf_test_run.h
> @@ -0,0 +1,50 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM bpf_test_run
> +
> +#if !defined(_TRACE_NBD_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_BPF_TEST_RUN_H
> +
> +#include <linux/tracepoint.h>
> +
> +DECLARE_EVENT_CLASS(bpf_test_finish,
> +
> +	TP_PROTO(int *err),
> +
> +	TP_ARGS(err),
> +
> +	TP_STRUCT__entry(
> +		__field(int, err)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->err = *err;
> +	),
> +
> +	TP_printk("bpf_test_finish with err=%d", __entry->err)
> +);
> +
> +#ifdef DEFINE_EVENT_WRITABLE
> +#undef BPF_TEST_RUN_DEFINE_EVENT
> +#define BPF_TEST_RUN_DEFINE_EVENT(template, call, proto, args, size)	\
> +	DEFINE_EVENT_WRITABLE(template, call, PARAMS(proto),		\
> +			      PARAMS(args), size)
> +#else
> +#undef BPF_TEST_RUN_DEFINE_EVENT
> +#define BPF_TEST_RUN_DEFINE_EVENT(template, call, proto, args, size)	\
> +	DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args))
> +#endif
> +
> +BPF_TEST_RUN_DEFINE_EVENT(bpf_test_finish, bpf_test_finish,
> +
> +	TP_PROTO(int *err),
> +
> +	TP_ARGS(err),
> +
> +	sizeof(int)
> +);
> +
> +#endif
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>
> diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
> index fab142b796ef..25e757102595 100644
> --- a/net/bpf/test_run.c
> +++ b/net/bpf/test_run.c
> @@ -13,6 +13,9 @@
>   #include <net/sock.h>
>   #include <net/tcp.h>
>   
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/bpf_test_run.h>
> +
>   static int bpf_test_run(struct bpf_prog *prog, void *ctx, u32 repeat,
>   			u32 *retval, u32 *time)
>   {
> @@ -100,6 +103,7 @@ static int bpf_test_finish(const union bpf_attr *kattr,
>   	if (err != -ENOSPC)
>   		err = 0;
>   out:
> +	trace_bpf_test_finish(&err);
>   	return err;
>   }
>   
> 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
> new file mode 100644
> index 000000000000..328d5c4b084b
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/raw_tp_writable_reject_nbd_invalid.c
> @@ -0,0 +1,40 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <test_progs.h>
> +#include <linux/nbd.h>
> +
> +void test_raw_tp_writable_reject_nbd_invalid(void)
> +{
> +	__u32 duration = 0;
> +	char error[4096];
> +	int bpf_fd = -1, tp_fd = -1;
> +
> +	const struct bpf_insn program[] = {
> +		/* r6 is our tp buffer */
> +		BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, 0),
> +		BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_6, 128),

The number "128" is a little cryptic. Maybe you can use something like
sizeof(struct nbd_request)?

> +		BPF_EXIT_INSN(),
> +	};
> +
> +	struct bpf_load_program_attr load_attr = {
> +		.prog_type = BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE,
> +		.license = "GPL v2",
> +		.insns = program,
> +		.insns_cnt = sizeof(program) / sizeof(struct bpf_insn),
> +		.log_level = 2,
> +	};
> +
> +	bpf_fd = bpf_load_program_xattr(&load_attr, error, sizeof(error));
> +	if (CHECK(bpf_fd < 0, "bpf_raw_tracepoint_writable loaded",
> +		  "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 opened",
> +		  "erroneously succeeded\n"))
> +		goto out_bpffd;
> +
> +	close(tp_fd);
> +out_bpffd:
> +	close(bpf_fd);
> +}
> diff --git a/tools/testing/selftests/bpf/prog_tests/raw_tp_writable_test_run.c b/tools/testing/selftests/bpf/prog_tests/raw_tp_writable_test_run.c
> new file mode 100644
> index 000000000000..4145925f9cab
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/raw_tp_writable_test_run.c
> @@ -0,0 +1,80 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <test_progs.h>
> +#include <linux/nbd.h>
> +
> +void test_raw_tp_writable_test_run(void)
> +{
> +	__u32 duration = 0;
> +	char error[4096];
> +
> +	const struct bpf_insn trace_program[] = {
> +		BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, 0),
> +		BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_6, 0),
> +		BPF_LD_IMM64(BPF_REG_0, 42),
You can use BPF_MOV64_IMM(BPF_REG_0, 42) instead of BPF_LD_IMM64.
BPF_LD_IMM64 is fine, but probably BPF_MOV64_IMM is better.
The same for a few below instances.

> +		BPF_STX_MEM(BPF_W, BPF_REG_6, BPF_REG_0, 0),
> +		BPF_EXIT_INSN(),
> +	};
> +
> +	struct bpf_load_program_attr load_attr = {
> +		.prog_type = BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE,
> +		.license = "GPL v2",
> +		.insns = trace_program,
> +		.insns_cnt = sizeof(trace_program) / sizeof(struct bpf_insn),
> +		.log_level = 2,
> +	};
> +
> +	int bpf_fd = bpf_load_program_xattr(&load_attr, error, sizeof(error));
> +	if (CHECK(bpf_fd < 0, "bpf_raw_tracepoint_writable loaded",
> +		  "failed: %d errno %d\n", bpf_fd, errno))
> +		return;
> +
> +	const struct bpf_insn skb_program[] = {
> +		BPF_LD_IMM64(BPF_REG_0, 0),
> +		BPF_EXIT_INSN(),
> +	};
> +
> +	struct bpf_load_program_attr skb_load_attr = {
> +		.prog_type = BPF_PROG_TYPE_SOCKET_FILTER,
> +		.license = "GPL v2",
> +		.insns = skb_program,
> +		.insns_cnt = sizeof(skb_program) / sizeof(struct bpf_insn),
> +	};
> +
> +	int filter_fd =
> +		bpf_load_program_xattr(&skb_load_attr, error, sizeof(error));
> +	if (CHECK(filter_fd < 0, "test_program_loaded", "failed: %d errno %d\n",
> +		  filter_fd, errno))
> +		goto out_bpffd;
> +
> +	int tp_fd = bpf_raw_tracepoint_open("bpf_test_finish", bpf_fd);
> +	if (CHECK(tp_fd < 0, "bpf_raw_tracepoint_writable opened",
> +		  "failed: %d errno %d\n", tp_fd, errno))
> +		goto out_filterfd;
> +
> +	char test_skb[128] = {
> +		0,
> +	};
> +
> +	__u32 prog_ret;
> +	int err = bpf_prog_test_run(filter_fd, 1, test_skb, sizeof(test_skb), 0,
> +				    0, &prog_ret, 0);
> +	CHECK(err != 42, "test_run",
> +	      "tracepoint did not modify return value\n");
> +	CHECK(prog_ret != 0, "test_run_ret",
> +	      "socket_filter did not return 0\n");
> +
> +	close(tp_fd);
> +
> +	err = bpf_prog_test_run(filter_fd, 1, test_skb, sizeof(test_skb), 0, 0,
> +				&prog_ret, 0);
> +	CHECK(err != 0, "test_run_notrace",
> +	      "test_run failed with %d errno %d\n", err, errno);
> +	CHECK(prog_ret != 0, "test_run_ret_notrace",
> +	      "socket_filter did not return 0\n");
> +
> +out_filterfd:
> +	close(filter_fd);
> +out_bpffd:
> +	close(bpf_fd);
> +}
> diff --git a/tools/testing/selftests/bpf/verifier/raw_tp_writable.c b/tools/testing/selftests/bpf/verifier/raw_tp_writable.c
> new file mode 100644
> index 000000000000..95b5d70a1dc1
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/verifier/raw_tp_writable.c
> @@ -0,0 +1,34 @@
> +{
> +	"raw_tracepoint_writable: reject variable offset",
> +	.insns = {
> +		/* r6 is our tp buffer */
> +		BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, 0),
> +
> +		BPF_LD_MAP_FD(BPF_REG_1, 0),
> +		/* move the key (== 0) to r10-8 */
> +		BPF_MOV32_IMM(BPF_REG_0, 0),
> +		BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
> +		BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
> +		BPF_STX_MEM(BPF_DW, BPF_REG_2, BPF_REG_0, 0),
> +		/* lookup in the map */
> +		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
> +			     BPF_FUNC_map_lookup_elem),
> +
> +		/* exit clean if null */
> +		BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
> +		BPF_EXIT_INSN(),
> +
> +		/* shift the buffer pointer to a variable location */
> +		BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_0, 0),
> +		BPF_ALU64_REG(BPF_ADD, BPF_REG_6, BPF_REG_0),
> +		/* clobber whatever's there */
> +		BPF_MOV64_IMM(BPF_REG_7, 4242),
> +		BPF_STX_MEM(BPF_DW, BPF_REG_6, BPF_REG_7, 0),
> +
> +		BPF_MOV64_IMM(BPF_REG_0, 0),
> +		BPF_EXIT_INSN(),
> +	},
> +	.fixup_map_hash_8b = { 1, },
> +	.prog_type = BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE,
> +	.errstr = "R6 invalid variable buffer offset: off=0, var_off=(0x0; 0xffffffff)",
> +},
> 

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