From: Chuyi Zhou <zhouchuyi@bytedance.com> mainline inclusion from mainline-v6.7-rc1 commit 3091b667498b0a212e760e1033e5f9b8c33a948f category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/IDC9YK Reference: https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commi... -------------------------------- The newly added open-coded css_task iter would try to hold the global css_set_lock in bpf_iter_css_task_new, so the bpf side has to be careful in where it allows to use this iter. The mainly concern is dead locking on css_set_lock. check_css_task_iter_allowlist() in verifier enforced css_task can only be used in bpf_lsm hooks and sleepable bpf_iter. This patch relax the allowlist for css_task iter. Any lsm and any iter (even non-sleepable) and any sleepable are safe since they would not hold the css_set_lock before entering BPF progs context. This patch also fixes the misused BPF_TRACE_ITER in check_css_task_iter_allowlist which compared bpf_prog_type with bpf_attach_type. Fixes: 9c66dc94b62ae ("bpf: Introduce css_task open-coded iterator kfuncs") Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com> Acked-by: Yonghong Song <yonghong.song@linux.dev> Link: https://lore.kernel.org/r/20231031050438.93297-2-zhouchuyi@bytedance.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Zicheng Qu <quzicheng@huawei.com> --- kernel/bpf/verifier.c | 16 ++++++++++++---- .../selftests/bpf/progs/iters_task_failure.c | 4 ++-- 2 files changed, 14 insertions(+), 6 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index bd2ca2ab5e5b..25da1dc82372 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -11425,6 +11425,12 @@ static int process_kf_arg_ptr_to_rbtree_node(struct bpf_verifier_env *env, &meta->arg_rbtree_root.field); } +/* + * css_task iter allowlist is needed to avoid dead locking on css_set_lock. + * LSM hooks and iters (both sleepable and non-sleepable) are safe. + * Any sleepable progs are also safe since bpf_check_attach_target() enforce + * them can only be attached to some specific hook points. + */ static bool check_css_task_iter_allowlist(struct bpf_verifier_env *env) { enum bpf_prog_type prog_type = resolve_prog_type(env->prog); @@ -11432,10 +11438,12 @@ static bool check_css_task_iter_allowlist(struct bpf_verifier_env *env) switch (prog_type) { case BPF_PROG_TYPE_LSM: return true; - case BPF_TRACE_ITER: - return env->prog->aux->sleepable; + case BPF_PROG_TYPE_TRACING: + if (env->prog->expected_attach_type == BPF_TRACE_ITER) + return true; + fallthrough; default: - return false; + return env->prog->aux->sleepable; } } @@ -11685,7 +11693,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ case KF_ARG_PTR_TO_ITER: if (meta->func_id == special_kfunc_list[KF_bpf_iter_css_task_new]) { if (!check_css_task_iter_allowlist(env)) { - verbose(env, "css_task_iter is only allowed in bpf_lsm and bpf iter-s\n"); + verbose(env, "css_task_iter is only allowed in bpf_lsm, bpf_iter and sleepable progs\n"); return -EINVAL; } } diff --git a/tools/testing/selftests/bpf/progs/iters_task_failure.c b/tools/testing/selftests/bpf/progs/iters_task_failure.c index c3bf96a67dba..6b1588d70652 100644 --- a/tools/testing/selftests/bpf/progs/iters_task_failure.c +++ b/tools/testing/selftests/bpf/progs/iters_task_failure.c @@ -84,8 +84,8 @@ int BPF_PROG(iter_css_lock_and_unlock) return 0; } -SEC("?fentry.s/" SYS_PREFIX "sys_getpgid") -__failure __msg("css_task_iter is only allowed in bpf_lsm and bpf iter-s") +SEC("?fentry/" SYS_PREFIX "sys_getpgid") +__failure __msg("css_task_iter is only allowed in bpf_lsm, bpf_iter and sleepable progs") int BPF_PROG(iter_css_task_for_each) { u64 cg_id = bpf_get_current_cgroup_id(); -- 2.34.1