diff options
author | Yonghong Song <yhs@fb.com> | 2020-05-09 10:59:16 -0700 |
---|---|---|
committer | Alexei Starovoitov <ast@kernel.org> | 2020-05-09 17:05:27 -0700 |
commit | 9c5f8a1008a121e4c6b24af211034e24b0b63081 (patch) | |
tree | 5bab59eab8c7aef4830ad807b30f617c007ec78b | |
parent | 1d68f22b3d53d368d5cc8d09de890250cae5c945 (diff) |
bpf: Support variable length array in tracing programs
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.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200509175916.2476853-1-yhs@fb.com
-rw-r--r-- | kernel/bpf/btf.c | 37 |
1 files changed, 37 insertions, 0 deletions
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 @@ again: 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; |