From: Björn Töpel bjorn.topel@gmail.com
commit c77b0589ca29ad1859fe7d7c1ecd63c0632379fa upstream
Some architectures have strict alignment requirements. In that case, the BPF verifier detects if a program has unaligned accesses and rejects them. A user can pass BPF_F_ANY_ALIGNMENT to a program to override this check. That, however, will only work when a privileged user loads a program. An unprivileged user loading a program with this flag will be rejected prior entering the verifier.
Hence, it does not make sense to load unprivileged programs without strict alignment when testing the verifier. This patch avoids exactly that.
Signed-off-by: Björn Töpel bjorn.topel@gmail.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Acked-by: Luke Nelson luke.r.nels@gmail.com Link: https://lore.kernel.org/bpf/20201118071640.83773-3-bjorn.topel@gmail.com Signed-off-by: Tiezhu Yang yangtiezhu@loongson.cn Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- tools/testing/selftests/bpf/test_verifier.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
--- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -13045,6 +13045,19 @@ static void get_unpriv_disabled()
static bool test_as_unpriv(struct bpf_test *test) { +#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS + /* Some architectures have strict alignment requirements. In + * that case, the BPF verifier detects if a program has + * unaligned accesses and rejects them. A user can pass + * BPF_F_ANY_ALIGNMENT to a program to override this + * check. That, however, will only work when a privileged user + * loads a program. An unprivileged user loading a program + * with this flag will be rejected prior entering the + * verifier. + */ + if (test->flags & F_NEEDS_EFFICIENT_UNALIGNED_ACCESS) + return false; +#endif return !test->prog_type || test->prog_type == BPF_PROG_TYPE_SOCKET_FILTER || test->prog_type == BPF_PROG_TYPE_CGROUP_SKB;