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From: Yonghong Song <yhs@fb.com>
To: Andrii Nakryiko <andriin@fb.com>, <bpf@vger.kernel.org>,
	Martin KaFai Lau <kafai@fb.com>, <netdev@vger.kernel.org>
Cc: Alexei Starovoitov <ast@fb.com>,
	Daniel Borkmann <daniel@iogearbox.net>, <kernel-team@fb.com>
Subject: [PATCH bpf-next v4 15/21] bpf: support variable length array in tracing programs
Date: Sat, 9 May 2020 10:59:16 -0700	[thread overview]
Message-ID: <20200509175916.2476853-1-yhs@fb.com> (raw)
In-Reply-To: <20200509175859.2474608-1-yhs@fb.com>

In /proc/net/ipv6_route, we have
  struct fib6_info {
    struct fib6_table *fib6_table;
    ...
    struct fib6_nh fib6_nh[0];
  }
  struct fib6_nh {
    struct fib_nh_common nh_common;
    struct rt6_info **rt6i_pcpu;
    struct rt6_exception_bucket *rt6i_exception_bucket;
  };
  struct fib_nh_common {
    ...
    u8 nhc_gw_family;
    ...
  }

The access:
  struct fib6_nh *fib6_nh = &rt->fib6_nh;
  ... fib6_nh->nh_common.nhc_gw_family ...

This patch ensures such an access is handled properly.

Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
---
 kernel/bpf/btf.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index c490fbde22d4..dcd233139294 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3833,6 +3833,7 @@ int btf_struct_access(struct bpf_verifier_log *log,
 	const struct btf_type *mtype, *elem_type = NULL;
 	const struct btf_member *member;
 	const char *tname, *mname;
+	u32 vlen;
 
 again:
 	tname = __btf_name_by_offset(btf_vmlinux, t->name_off);
@@ -3841,7 +3842,43 @@ int btf_struct_access(struct bpf_verifier_log *log,
 		return -EINVAL;
 	}
 
+	vlen = btf_type_vlen(t);
 	if (off + size > t->size) {
+		/* If the last element is a variable size array, we may
+		 * need to relax the rule.
+		 */
+		struct btf_array *array_elem;
+
+		if (vlen == 0)
+			goto error;
+
+		member = btf_type_member(t) + vlen - 1;
+		mtype = btf_type_skip_modifiers(btf_vmlinux, member->type,
+						NULL);
+		if (!btf_type_is_array(mtype))
+			goto error;
+
+		array_elem = (struct btf_array *)(mtype + 1);
+		if (array_elem->nelems != 0)
+			goto error;
+
+		moff = btf_member_bit_offset(t, member) / 8;
+		if (off < moff)
+			goto error;
+
+		/* Only allow structure for now, can be relaxed for
+		 * other types later.
+		 */
+		elem_type = btf_type_skip_modifiers(btf_vmlinux,
+						    array_elem->type, NULL);
+		if (!btf_type_is_struct(elem_type))
+			goto error;
+
+		off = (off - moff) % elem_type->size;
+		return btf_struct_access(log, elem_type, off, size, atype,
+					 next_btf_id);
+
+error:
 		bpf_log(log, "access beyond struct %s at off %u size %u\n",
 			tname, off, size);
 		return -EACCES;
-- 
2.24.1


  parent reply	other threads:[~2020-05-09 17:59 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-09 17:58 [PATCH bpf-next v4 00/21] bpf: implement bpf iterator for kernel data Yonghong Song
2020-05-09 17:58 ` [PATCH bpf-next v4 01/21] bpf: implement an interface to register bpf_iter targets Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 02/21] bpf: allow loading of a bpf_iter program Yonghong Song
2020-05-10  0:41   ` Alexei Starovoitov
2020-05-10  5:07     ` Yonghong Song
2020-05-12 15:41     ` Yonghong Song
2020-05-12 16:25       ` Alexei Starovoitov
2020-05-12 16:29         ` Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 03/21] bpf: support bpf tracing/iter programs for BPF_LINK_CREATE Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 04/21] bpf: support bpf tracing/iter programs for BPF_LINK_UPDATE Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 05/21] bpf: implement bpf_seq_read() for bpf iterator Yonghong Song
2020-05-10  0:30   ` Alexei Starovoitov
2020-05-10  4:51     ` Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 06/21] bpf: create anonymous " Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 07/21] bpf: create file " Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 08/21] bpf: implement common macros/helpers for target iterators Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 09/21] bpf: add bpf_map iterator Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 10/21] net: bpf: add netlink and ipv6_route bpf_iter targets Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 11/21] bpf: add task and task/file iterator targets Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 12/21] bpf: add PTR_TO_BTF_ID_OR_NULL support Yonghong Song
2020-05-10  0:50   ` Alexei Starovoitov
2020-05-10  5:18     ` Yonghong Song
2020-05-10 16:11       ` Alexei Starovoitov
2020-05-10 17:05         ` Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 13/21] bpf: add bpf_seq_printf and bpf_seq_write helpers Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 14/21] bpf: handle spilled PTR_TO_BTF_ID properly when checking stack_boundary Yonghong Song
2020-05-09 17:59 ` Yonghong Song [this message]
2020-05-09 17:59 ` [PATCH bpf-next v4 16/21] tools/libbpf: add bpf_iter support Yonghong Song
2020-05-10  0:35   ` Alexei Starovoitov
2020-05-10  5:06     ` Yonghong Song
2020-05-10 16:09       ` Alexei Starovoitov
2020-05-10 17:04         ` Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 17/21] tools/libpf: add offsetof/container_of macro in bpf_helpers.h Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 18/21] tools/bpftool: add bpf_iter support for bptool Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 19/21] tools/bpf: selftests: add iterator programs for ipv6_route and netlink Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 20/21] tools/bpf: selftests: add iter progs for bpf_map/task/task_file Yonghong Song
2020-05-09 17:59 ` [PATCH bpf-next v4 21/21] tools/bpf: selftests: add bpf_iter selftests Yonghong Song
2020-05-10  0:34   ` Alexei Starovoitov
2020-05-10  5:01     ` Yonghong Song
2020-05-10 16:14       ` Alexei Starovoitov
2020-05-10  0:27 ` [PATCH bpf-next v4 00/21] bpf: implement bpf iterator for kernel data Alexei Starovoitov
2020-05-10  4:47   ` Yonghong Song

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