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bpf: Dont allow vmlinux BTF to be used in map_create and prog_load.

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The syzbot got FD of vmlinux BTF and passed it into map_create which caused
crash in btf_type_id_size() when it tried to access resolved_ids. The vmlinux
BTF doesn't have 'resolved_ids' and 'resolved_sizes' initialized to save
memory. To avoid such issues disallow using vmlinux BTF in prog_load and
map_create commands.

Fixes: 5329722057 ("bpf: Assign ID to vmlinux BTF and return extra info for BTF in GET_OBJ_INFO")
Reported-by: syzbot+8bab8ed346746e7540e8@syzkaller.appspotmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210307225248.79031-1-alexei.starovoitov@gmail.com
This commit is contained in:
Alexei Starovoitov 2021-03-07 14:52:48 -08:00 committed by Daniel Borkmann
parent edbea92202
commit 350a5c4dd2
2 changed files with 9 additions and 0 deletions
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5
kernel/bpf/syscall.c
View File

@ -854,6 +854,11 @@ static int map_create(union bpf_attr *attr)
err = PTR_ERR(btf);
goto free_map;
}
if (btf_is_kernel(btf)) {
btf_put(btf);
err = -EACCES;
goto free_map;
}
map->btf = btf;
if (attr->btf_value_type_id) {

4
kernel/bpf/verifier.c
View File

@ -9056,6 +9056,10 @@ static int check_btf_info(struct bpf_verifier_env *env,
btf = btf_get_by_fd(attr->prog_btf_fd);
if (IS_ERR(btf))
return PTR_ERR(btf);
if (btf_is_kernel(btf)) {
btf_put(btf);
return -EACCES;
}
env->prog->aux->btf = btf;
err = check_btf_func(env, attr, uattr);