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bpf: btf: Ensure the member->offset is in the right order 

This patch ensures the member->offset of a struct
is in the correct order (i.e the later member's offset cannot
go backward).

The current "pahole -J" BTF encoder does not generate something
like this.  However, checking this can ensure future encoder
will not violate this.

Fixes: 69b693f0ae ("bpf: btf: Introduce BPF Type Format (BTF)")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Martin KaFai Lau 2018-07-20 17:38:37 -07:00 committed by Daniel Borkmann
parent 1a4f14bab1
commit 6283fa38dc
2 changed files with 41 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
kernel/bpf/btf.c
View File

@ -1519,9 +1519,9 @@ static s32 btf_struct_check_meta(struct btf_verifier_env *env,
{
bool is_union = BTF_INFO_KIND(t->info) == BTF_KIND_UNION;
const struct btf_member *member;
u32 meta_needed, last_offset;
struct btf *btf = env->btf;
u32 struct_size = t->size;
u32 meta_needed;
u16 i;
meta_needed = btf_type_vlen(t) * sizeof(*member);
@ -1534,6 +1534,7 @@ static s32 btf_struct_check_meta(struct btf_verifier_env *env,
btf_verifier_log_type(env, t, NULL);
last_offset = 0;
for_each_member(i, t, member) {
if (!btf_name_offset_valid(btf, member->name_off)) {
btf_verifier_log_member(env, t, member,
@ -1555,6 +1556,16 @@ static s32 btf_struct_check_meta(struct btf_verifier_env *env,
return -EINVAL;
}
/*
* ">" instead of ">=" because the last member could be
* "char a[0];"
*/
if (last_offset > member->offset) {
btf_verifier_log_member(env, t, member,
"Invalid member bits_offset");
return -EINVAL;
}
if (BITS_ROUNDUP_BYTES(member->offset) > struct_size) {
btf_verifier_log_member(env, t, member,
"Memmber bits_offset exceeds its struct size");
@ -1562,6 +1573,7 @@ static s32 btf_struct_check_meta(struct btf_verifier_env *env,
}
btf_verifier_log_member(env, t, member, NULL);
last_offset = member->offset;
}
return meta_needed;

28
tools/testing/selftests/bpf/test_btf.c
View File

@ -247,6 +247,34 @@ static struct btf_raw_test raw_tests[] = {
.max_entries = 4,
},
{
.descr = "struct test #3 Invalid member offset",
.raw_types = {
/* int */ /* [1] */
BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),
/* int64 */ /* [2] */
BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 64, 8),
/* struct A { */ /* [3] */
BTF_TYPE_ENC(NAME_TBD, BTF_INFO_ENC(BTF_KIND_STRUCT, 0, 2), 16),
BTF_MEMBER_ENC(NAME_TBD, 1, 64), /* int m; */
BTF_MEMBER_ENC(NAME_TBD, 2, 0), /* int64 n; */
/* } */
BTF_END_RAW,
},
.str_sec = "\0A\0m\0n\0",
.str_sec_size = sizeof("\0A\0m\0n\0"),
.map_type = BPF_MAP_TYPE_ARRAY,
.map_name = "struct_test3_map",
.key_size = sizeof(int),
.value_size = 16,
.key_type_id = 1,
.value_type_id = 3,
.max_entries = 4,
.btf_load_err = true,
.err_str = "Invalid member bits_offset",
},
/* Test member exceeds the size of struct.
*
* struct A {