| Message ID | 20221217082506.1570898-10-davemarchevsky@fb.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF |
| Headers | show |
| Series | BPF rbtree next-gen datastructure | expand |
On Sat, Dec 17, 2022 at 12:25:02AM -0800, Dave Marchevsky wrote: > Newly-added bpf_rbtree_{remove,first} kfuncs have some special properties > that require handling in the verifier: > > * both bpf_rbtree_remove and bpf_rbtree_first return the type containing > the bpf_rb_node field, with the offset set to that field's offset, > instead of a struct bpf_rb_node * > * mark_reg_graph_node helper added in previous patch generalizes > this logic, use it > > * bpf_rbtree_remove's node input is a node that's been inserted > in the tree - a non-owning reference. > > * bpf_rbtree_remove must invalidate non-owning references in order to > avoid aliasing issue. Add KF_INVALIDATE_NON_OWN flag, which > indicates that the marked kfunc is a non-owning ref invalidation > point, and associated verifier logic using previously-added > invalidate_non_owning_refs helper. > > * Unlike other functions, which convert one of their input arg regs to > non-owning reference, bpf_rbtree_first takes no arguments and just > returns a non-owning reference (possibly null) > * For now verifier logic for this is special-cased instead of > adding new kfunc flag. > > This patch, along with the previous one, complete special verifier > handling for all rbtree API functions added in this series. > > Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com> > --- > include/linux/btf.h | 1 + > kernel/bpf/helpers.c | 2 +- > kernel/bpf/verifier.c | 34 ++++++++++++++++++++++++++++------ > 3 files changed, 30 insertions(+), 7 deletions(-) > > diff --git a/include/linux/btf.h b/include/linux/btf.h > index 8aee3f7f4248..3663911bb7c0 100644 > --- a/include/linux/btf.h > +++ b/include/linux/btf.h > @@ -72,6 +72,7 @@ > #define KF_DESTRUCTIVE (1 << 6) /* kfunc performs destructive actions */ > #define KF_RCU (1 << 7) /* kfunc only takes rcu pointer arguments */ > #define KF_RELEASE_NON_OWN (1 << 8) /* kfunc converts its referenced arg into non-owning ref */ > +#define KF_INVALIDATE_NON_OWN (1 << 9) /* kfunc invalidates non-owning refs after return */ > > /* > * Return the name of the passed struct, if exists, or halt the build if for > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > index de4523c777b7..0e6d010e6423 100644 > --- a/kernel/bpf/helpers.c > +++ b/kernel/bpf/helpers.c > @@ -2121,7 +2121,7 @@ BTF_ID_FLAGS(func, bpf_task_acquire, KF_ACQUIRE | KF_TRUSTED_ARGS) > BTF_ID_FLAGS(func, bpf_task_acquire_not_zero, KF_ACQUIRE | KF_RCU | KF_RET_NULL) > BTF_ID_FLAGS(func, bpf_task_kptr_get, KF_ACQUIRE | KF_KPTR_GET | KF_RET_NULL) > BTF_ID_FLAGS(func, bpf_task_release, KF_RELEASE) > -BTF_ID_FLAGS(func, bpf_rbtree_remove, KF_ACQUIRE) > +BTF_ID_FLAGS(func, bpf_rbtree_remove, KF_ACQUIRE | KF_INVALIDATE_NON_OWN) I don't like this 'generalization' either. > BTF_ID_FLAGS(func, bpf_rbtree_add, KF_RELEASE | KF_RELEASE_NON_OWN) > BTF_ID_FLAGS(func, bpf_rbtree_first, KF_RET_NULL) > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index 75979f78399d..b4bf3701de7f 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -8393,6 +8393,11 @@ static bool is_kfunc_release_non_own(struct bpf_kfunc_call_arg_meta *meta) > return meta->kfunc_flags & KF_RELEASE_NON_OWN; > } > > +static bool is_kfunc_invalidate_non_own(struct bpf_kfunc_call_arg_meta *meta) > +{ > + return meta->kfunc_flags & KF_INVALIDATE_NON_OWN; > +} > + > static bool is_kfunc_trusted_args(struct bpf_kfunc_call_arg_meta *meta) > { > return meta->kfunc_flags & KF_TRUSTED_ARGS; > @@ -9425,10 +9430,20 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ > verbose(env, "arg#%d expected pointer to allocated object\n", i); > return -EINVAL; > } > - if (!reg->ref_obj_id) { > + if (meta->func_id == special_kfunc_list[KF_bpf_rbtree_remove]) { > + if (reg->ref_obj_id) { > + verbose(env, "rbtree_remove node input must be non-owning ref\n"); > + return -EINVAL; > + } > + if (in_rbtree_lock_required_cb(env)) { > + verbose(env, "rbtree_remove not allowed in rbtree cb\n"); > + return -EINVAL; > + } > + } else if (!reg->ref_obj_id) { > verbose(env, "allocated object must be referenced\n"); > return -EINVAL; > } > + > ret = process_kf_arg_ptr_to_rbtree_node(env, reg, regno, meta); > if (ret < 0) > return ret; > @@ -9665,11 +9680,12 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, > meta.func_id == special_kfunc_list[KF_bpf_list_pop_back]) { > struct btf_field *field = meta.arg_list_head.field; > > - mark_reg_known_zero(env, regs, BPF_REG_0); > - regs[BPF_REG_0].type = PTR_TO_BTF_ID | MEM_ALLOC; > - regs[BPF_REG_0].btf = field->graph_root.btf; > - regs[BPF_REG_0].btf_id = field->graph_root.value_btf_id; > - regs[BPF_REG_0].off = field->graph_root.node_offset; > + mark_reg_graph_node(regs, BPF_REG_0, &field->graph_root); > + } else if (meta.func_id == special_kfunc_list[KF_bpf_rbtree_remove] || Just call invalidate_non_owning_refs() here since it needs to be a special case anyway. > + meta.func_id == special_kfunc_list[KF_bpf_rbtree_first]) { > + struct btf_field *field = meta.arg_rbtree_root.field; > + > + mark_reg_graph_node(regs, BPF_REG_0, &field->graph_root); > } else if (meta.func_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx]) { > mark_reg_known_zero(env, regs, BPF_REG_0); > regs[BPF_REG_0].type = PTR_TO_BTF_ID | PTR_TRUSTED; > @@ -9735,7 +9751,13 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, > if (is_kfunc_ret_null(&meta)) > regs[BPF_REG_0].id = id; > regs[BPF_REG_0].ref_obj_id = id; > + } else if (meta.func_id == special_kfunc_list[KF_bpf_rbtree_first]) { > + ref_set_non_owning_lock(env, ®s[BPF_REG_0]); > } > + > + if (is_kfunc_invalidate_non_own(&meta)) > + invalidate_non_owning_refs(env, &env->cur_state->active_lock); > + > if (reg_may_point_to_spin_lock(®s[BPF_REG_0]) && !regs[BPF_REG_0].id) > regs[BPF_REG_0].id = ++env->id_gen; > } /* else { add_kfunc_call() ensures it is btf_type_is_void(t) } */ > -- > 2.30.2 >
diff --git a/include/linux/btf.h b/include/linux/btf.h index 8aee3f7f4248..3663911bb7c0 100644 --- a/include/linux/btf.h +++ b/include/linux/btf.h @@ -72,6 +72,7 @@ #define KF_DESTRUCTIVE (1 << 6) /* kfunc performs destructive actions */ #define KF_RCU (1 << 7) /* kfunc only takes rcu pointer arguments */ #define KF_RELEASE_NON_OWN (1 << 8) /* kfunc converts its referenced arg into non-owning ref */ +#define KF_INVALIDATE_NON_OWN (1 << 9) /* kfunc invalidates non-owning refs after return */ /* * Return the name of the passed struct, if exists, or halt the build if for diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index de4523c777b7..0e6d010e6423 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2121,7 +2121,7 @@ BTF_ID_FLAGS(func, bpf_task_acquire, KF_ACQUIRE | KF_TRUSTED_ARGS) BTF_ID_FLAGS(func, bpf_task_acquire_not_zero, KF_ACQUIRE | KF_RCU | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_task_kptr_get, KF_ACQUIRE | KF_KPTR_GET | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_task_release, KF_RELEASE) -BTF_ID_FLAGS(func, bpf_rbtree_remove, KF_ACQUIRE) +BTF_ID_FLAGS(func, bpf_rbtree_remove, KF_ACQUIRE | KF_INVALIDATE_NON_OWN) BTF_ID_FLAGS(func, bpf_rbtree_add, KF_RELEASE | KF_RELEASE_NON_OWN) BTF_ID_FLAGS(func, bpf_rbtree_first, KF_RET_NULL) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 75979f78399d..b4bf3701de7f 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -8393,6 +8393,11 @@ static bool is_kfunc_release_non_own(struct bpf_kfunc_call_arg_meta *meta) return meta->kfunc_flags & KF_RELEASE_NON_OWN; } +static bool is_kfunc_invalidate_non_own(struct bpf_kfunc_call_arg_meta *meta) +{ + return meta->kfunc_flags & KF_INVALIDATE_NON_OWN; +} + static bool is_kfunc_trusted_args(struct bpf_kfunc_call_arg_meta *meta) { return meta->kfunc_flags & KF_TRUSTED_ARGS; @@ -9425,10 +9430,20 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ verbose(env, "arg#%d expected pointer to allocated object\n", i); return -EINVAL; } - if (!reg->ref_obj_id) { + if (meta->func_id == special_kfunc_list[KF_bpf_rbtree_remove]) { + if (reg->ref_obj_id) { + verbose(env, "rbtree_remove node input must be non-owning ref\n"); + return -EINVAL; + } + if (in_rbtree_lock_required_cb(env)) { + verbose(env, "rbtree_remove not allowed in rbtree cb\n"); + return -EINVAL; + } + } else if (!reg->ref_obj_id) { verbose(env, "allocated object must be referenced\n"); return -EINVAL; } + ret = process_kf_arg_ptr_to_rbtree_node(env, reg, regno, meta); if (ret < 0) return ret; @@ -9665,11 +9680,12 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, meta.func_id == special_kfunc_list[KF_bpf_list_pop_back]) { struct btf_field *field = meta.arg_list_head.field; - mark_reg_known_zero(env, regs, BPF_REG_0); - regs[BPF_REG_0].type = PTR_TO_BTF_ID | MEM_ALLOC; - regs[BPF_REG_0].btf = field->graph_root.btf; - regs[BPF_REG_0].btf_id = field->graph_root.value_btf_id; - regs[BPF_REG_0].off = field->graph_root.node_offset; + mark_reg_graph_node(regs, BPF_REG_0, &field->graph_root); + } else if (meta.func_id == special_kfunc_list[KF_bpf_rbtree_remove] || + meta.func_id == special_kfunc_list[KF_bpf_rbtree_first]) { + struct btf_field *field = meta.arg_rbtree_root.field; + + mark_reg_graph_node(regs, BPF_REG_0, &field->graph_root); } else if (meta.func_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx]) { mark_reg_known_zero(env, regs, BPF_REG_0); regs[BPF_REG_0].type = PTR_TO_BTF_ID | PTR_TRUSTED; @@ -9735,7 +9751,13 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, if (is_kfunc_ret_null(&meta)) regs[BPF_REG_0].id = id; regs[BPF_REG_0].ref_obj_id = id; + } else if (meta.func_id == special_kfunc_list[KF_bpf_rbtree_first]) { + ref_set_non_owning_lock(env, ®s[BPF_REG_0]); } + + if (is_kfunc_invalidate_non_own(&meta)) + invalidate_non_owning_refs(env, &env->cur_state->active_lock); + if (reg_may_point_to_spin_lock(®s[BPF_REG_0]) && !regs[BPF_REG_0].id) regs[BPF_REG_0].id = ++env->id_gen; } /* else { add_kfunc_call() ensures it is btf_type_is_void(t) } */
Newly-added bpf_rbtree_{remove,first} kfuncs have some special properties that require handling in the verifier: * both bpf_rbtree_remove and bpf_rbtree_first return the type containing the bpf_rb_node field, with the offset set to that field's offset, instead of a struct bpf_rb_node * * mark_reg_graph_node helper added in previous patch generalizes this logic, use it * bpf_rbtree_remove's node input is a node that's been inserted in the tree - a non-owning reference. * bpf_rbtree_remove must invalidate non-owning references in order to avoid aliasing issue. Add KF_INVALIDATE_NON_OWN flag, which indicates that the marked kfunc is a non-owning ref invalidation point, and associated verifier logic using previously-added invalidate_non_owning_refs helper. * Unlike other functions, which convert one of their input arg regs to non-owning reference, bpf_rbtree_first takes no arguments and just returns a non-owning reference (possibly null) * For now verifier logic for this is special-cased instead of adding new kfunc flag. This patch, along with the previous one, complete special verifier handling for all rbtree API functions added in this series. Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com> --- include/linux/btf.h | 1 + kernel/bpf/helpers.c | 2 +- kernel/bpf/verifier.c | 34 ++++++++++++++++++++++++++++------ 3 files changed, 30 insertions(+), 7 deletions(-)