From: Alexei Starovoitov Date: Sun, 7 Mar 2021 22:52:48 +0000 (-0800) Subject: bpf: Dont allow vmlinux BTF to be used in map_create and prog_load. X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=350a5c4dd2452ea999cc5e1d4a8dbf12de2f97ef;p=linux.git bpf: Dont allow vmlinux BTF to be used in map_create and prog_load. 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: 5329722057d4 ("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 Signed-off-by: Daniel Borkmann Acked-by: Yonghong Song Link: https://lore.kernel.org/bpf/20210307225248.79031-1-alexei.starovoitov@gmail.com --- diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index c859bc46d06ca..250503482cda2 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -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) { diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index c56e3fcb5f1a0..4192a9e566542 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -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);