diff options
| -rw-r--r-- | Documentation/bpf/kfuncs.rst | 19 | ||||
| -rw-r--r-- | kernel/bpf/verifier.c | 10 | ||||
| -rw-r--r-- | tools/testing/selftests/bpf/progs/cgroup_read_xattr.c | 2 | ||||
| -rw-r--r-- | tools/testing/selftests/bpf/progs/iters_task_failure.c | 4 |
4 files changed, 31 insertions, 4 deletions
diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst index ae468b781d31..e38941370b90 100644 --- a/Documentation/bpf/kfuncs.rst +++ b/Documentation/bpf/kfuncs.rst @@ -335,9 +335,26 @@ consider doing refcnt != 0 check, especially when returning a KF_ACQUIRE pointer. Note as well that a KF_ACQUIRE kfunc that is KF_RCU should very likely also be KF_RET_NULL. +2.4.8 KF_RCU_PROTECTED flag +--------------------------- + +The KF_RCU_PROTECTED flag is used to indicate that the kfunc must be invoked in +an RCU critical section. This is assumed by default in non-sleepable programs, +and must be explicitly ensured by calling ``bpf_rcu_read_lock`` for sleepable +ones. + +If the kfunc returns a pointer value, this flag also enforces that the returned +pointer is RCU protected, and can only be used while the RCU critical section is +active. + +The flag is distinct from the ``KF_RCU`` flag, which only ensures that its +arguments are at least RCU protected pointers. This may transitively imply that +RCU protection is ensured, but it does not work in cases of kfuncs which require +RCU protection but do not take RCU protected arguments. + .. _KF_deprecated_flag: -2.4.8 KF_DEPRECATED flag +2.4.9 KF_DEPRECATED flag ------------------------ The KF_DEPRECATED flag is used for kfuncs which are scheduled to be diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index beaa391e02fb..6625570ac23d 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -13931,6 +13931,11 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, return -EACCES; } + if (is_kfunc_rcu_protected(&meta) && !in_rcu_cs(env)) { + verbose(env, "kernel func %s requires RCU critical section protection\n", func_name); + return -EACCES; + } + /* In case of release function, we get register number of refcounted * PTR_TO_BTF_ID in bpf_kfunc_arg_meta, do the release now. */ @@ -14044,6 +14049,9 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, /* Ensures we don't access the memory after a release_reference() */ if (meta.ref_obj_id) regs[BPF_REG_0].ref_obj_id = meta.ref_obj_id; + + if (is_kfunc_rcu_protected(&meta)) + regs[BPF_REG_0].type |= MEM_RCU; } else { mark_reg_known_zero(env, regs, BPF_REG_0); regs[BPF_REG_0].btf = desc_btf; @@ -14052,6 +14060,8 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, if (meta.func_id == special_kfunc_list[KF_bpf_get_kmem_cache]) regs[BPF_REG_0].type |= PTR_UNTRUSTED; + else if (is_kfunc_rcu_protected(&meta)) + regs[BPF_REG_0].type |= MEM_RCU; if (is_iter_next_kfunc(&meta)) { struct bpf_reg_state *cur_iter; diff --git a/tools/testing/selftests/bpf/progs/cgroup_read_xattr.c b/tools/testing/selftests/bpf/progs/cgroup_read_xattr.c index 092db1d0435e..88e13e17ec9e 100644 --- a/tools/testing/selftests/bpf/progs/cgroup_read_xattr.c +++ b/tools/testing/selftests/bpf/progs/cgroup_read_xattr.c @@ -73,7 +73,7 @@ int BPF_PROG(use_css_iter_non_sleepable) } SEC("lsm.s/socket_connect") -__failure __msg("expected an RCU CS") +__failure __msg("kernel func bpf_iter_css_new requires RCU critical section protection") int BPF_PROG(use_css_iter_sleepable_missing_rcu_lock) { u64 cgrp_id = bpf_get_current_cgroup_id(); diff --git a/tools/testing/selftests/bpf/progs/iters_task_failure.c b/tools/testing/selftests/bpf/progs/iters_task_failure.c index 6b1588d70652..fe3663dedbe1 100644 --- a/tools/testing/selftests/bpf/progs/iters_task_failure.c +++ b/tools/testing/selftests/bpf/progs/iters_task_failure.c @@ -15,7 +15,7 @@ void bpf_rcu_read_lock(void) __ksym; void bpf_rcu_read_unlock(void) __ksym; SEC("?fentry.s/" SYS_PREFIX "sys_getpgid") -__failure __msg("expected an RCU CS when using bpf_iter_task_next") +__failure __msg("kernel func bpf_iter_task_new requires RCU critical section protection") int BPF_PROG(iter_tasks_without_lock) { struct task_struct *pos; @@ -27,7 +27,7 @@ int BPF_PROG(iter_tasks_without_lock) } SEC("?fentry.s/" SYS_PREFIX "sys_getpgid") -__failure __msg("expected an RCU CS when using bpf_iter_css_next") +__failure __msg("kernel func bpf_iter_css_new requires RCU critical section protection") int BPF_PROG(iter_css_without_lock) { u64 cg_id = bpf_get_current_cgroup_id(); |