To support sleepable async callbacks, we need to tell push_async_cb()
whether the cb is sleepable or not.
The verifier now detects that we are in bpf_wq_set_callback_impl and
can allow a sleepable callback to happen.
Signed-off-by: Benjamin Tissoires <bentiss@xxxxxxxxxx>
---
changes in v2:
- dropped flags check for sleepable
- squashed with v1 14/18 as there is no point in having it separated now
---
include/linux/bpf_verifier.h | 1 +
kernel/bpf/helpers.c | 15 +++++++++
kernel/bpf/verifier.c | 75 ++++++++++++++++++++++++++++++++++++++++----
3 files changed, 85 insertions(+), 6 deletions(-)
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 36d19cd32eb5..9db35530c878 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -426,6 +426,7 @@ struct bpf_verifier_state {
* while they are still in use.
*/
bool used_as_loop_entry;
+ bool in_sleepable;
/* first and last insn idx of this verifier state */
u32 first_insn_idx;
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index b12486adc47a..85d3f483f27f 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2711,6 +2711,20 @@ __bpf_kfunc int bpf_wq_init(struct bpf_wq *wq, void *p__map, unsigned int flags)
return __bpf_async_init(async, map, flags, BPF_ASYNC_TYPE_WQ);
}
+__bpf_kfunc int bpf_wq_set_callback_impl(struct bpf_wq *wq,
+ int (callback_fn)(void *map, int *key, struct bpf_wq *wq),
+ unsigned int flags,
+ void *aux__ign)
+{
+ struct bpf_prog_aux *aux = (struct bpf_prog_aux *)aux__ign;
+ struct bpf_async_kern *async = (struct bpf_async_kern *)wq;
+
+ if (flags)
+ return -EINVAL;
+
+ return __bpf_async_set_callback(async, callback_fn, aux, flags, BPF_ASYNC_TYPE_WQ);
+}
+
__bpf_kfunc_end_defs();
BTF_KFUNCS_START(generic_btf_ids)
@@ -2789,6 +2803,7 @@ BTF_ID_FLAGS(func, bpf_dynptr_size)
BTF_ID_FLAGS(func, bpf_dynptr_clone)
BTF_ID_FLAGS(func, bpf_modify_return_test_tp)
BTF_ID_FLAGS(func, bpf_wq_init)
+BTF_ID_FLAGS(func, bpf_wq_set_callback_impl)
BTF_KFUNCS_END(common_btf_ids)
static const struct btf_kfunc_id_set common_kfunc_set = {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 5ff7b52d9032..e8603cff395b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -501,8 +501,12 @@ static bool is_dynptr_ref_function(enum bpf_func_id func_id)
}
static bool is_sync_callback_calling_kfunc(u32 btf_id);
+static bool is_async_callback_calling_kfunc(u32 btf_id);
+static bool is_callback_calling_kfunc(u32 btf_id);
static bool is_bpf_throw_kfunc(struct bpf_insn *insn);
+static bool is_bpf_wq_set_callback_impl_kfunc(u32 btf_id);
+
static bool is_sync_callback_calling_function(enum bpf_func_id func_id)
{
return func_id == BPF_FUNC_for_each_map_elem ||
@@ -530,7 +534,8 @@ static bool is_sync_callback_calling_insn(struct bpf_insn *insn)
static bool is_async_callback_calling_insn(struct bpf_insn *insn)
{
- return bpf_helper_call(insn) && is_async_callback_calling_function(insn->imm);
+ return (bpf_helper_call(insn) && is_async_callback_calling_function(insn->imm)) ||
+ (bpf_pseudo_kfunc_call(insn) && is_async_callback_calling_kfunc(insn->imm));
}
static bool is_may_goto_insn(struct bpf_insn *insn)
@@ -1429,6 +1434,7 @@ static int copy_verifier_state(struct bpf_verifier_state *dst_state,
}
dst_state->speculative = src->speculative;
dst_state->active_rcu_lock = src->active_rcu_lock;
+ dst_state->in_sleepable = src->in_sleepable;
dst_state->curframe = src->curframe;
dst_state->active_lock.ptr = src->active_lock.ptr;
dst_state->active_lock.id = src->active_lock.id;
@@ -2404,7 +2410,7 @@ static void init_func_state(struct bpf_verifier_env *env,
/* Similar to push_stack(), but for async callbacks */
static struct bpf_verifier_state *push_async_cb(struct bpf_verifier_env *env,
int insn_idx, int prev_insn_idx,
- int subprog)
+ int subprog, bool is_sleepable)
{
struct bpf_verifier_stack_elem *elem;
struct bpf_func_state *frame;
@@ -2431,6 +2437,7 @@ static struct bpf_verifier_state *push_async_cb(struct bpf_verifier_env *env,
* Initialize it similar to do_check_common().
*/
elem->st.branches = 1;
+ elem->st.in_sleepable = is_sleepable;
frame = kzalloc(sizeof(*frame), GFP_KERNEL);
if (!frame)
goto err;
@@ -5278,7 +5285,8 @@ static int map_kptr_match_type(struct bpf_verifier_env *env,
static bool in_sleepable(struct bpf_verifier_env *env)
{
- return env->prog->sleepable;
+ return env->prog->sleepable ||
+ (env->cur_state && env->cur_state->in_sleepable);
}
/* The non-sleepable programs and sleepable programs with explicit bpf_rcu_read_lock()
@@ -9513,7 +9521,7 @@ static int push_callback_call(struct bpf_verifier_env *env, struct bpf_insn *ins
*/
env->subprog_info[subprog].is_cb = true;
if (bpf_pseudo_kfunc_call(insn) &&
- !is_sync_callback_calling_kfunc(insn->imm)) {
+ !is_callback_calling_kfunc(insn->imm)) {
verbose(env, "verifier bug: kfunc %s#%d not marked as callback-calling\n",
func_id_name(insn->imm), insn->imm);
return -EFAULT;
@@ -9527,10 +9535,11 @@ static int push_callback_call(struct bpf_verifier_env *env, struct bpf_insn *ins
if (is_async_callback_calling_insn(insn)) {
struct bpf_verifier_state *async_cb;
- /* there is no real recursion here. timer callbacks are async */
+ /* there is no real recursion here. timer and workqueue callbacks are async */
env->subprog_info[subprog].is_async_cb = true;
async_cb = push_async_cb(env, env->subprog_info[subprog].start,
- insn_idx, subprog);
+ insn_idx, subprog,
+ is_bpf_wq_set_callback_impl_kfunc(insn->imm));
if (!async_cb)
return -EFAULT;
callee = async_cb->frame[0];
@@ -11018,6 +11027,7 @@ enum special_kfunc_type {
KF_bpf_percpu_obj_drop_impl,
KF_bpf_throw,
KF_bpf_iter_css_task_new,
+ KF_bpf_wq_set_callback_impl,
};
BTF_SET_START(special_kfunc_set)
@@ -11044,6 +11054,7 @@ BTF_ID(func, bpf_throw)
#ifdef CONFIG_CGROUPS
BTF_ID(func, bpf_iter_css_task_new)
#endif
+BTF_ID(func, bpf_wq_set_callback_impl)
BTF_SET_END(special_kfunc_set)
BTF_ID_LIST(special_kfunc_list)
@@ -11074,6 +11085,7 @@ BTF_ID(func, bpf_iter_css_task_new)
#else
BTF_ID_UNUSED
#endif
+BTF_ID(func, bpf_wq_set_callback_impl)
static bool is_kfunc_ret_null(struct bpf_kfunc_call_arg_meta *meta)
{
@@ -11402,12 +11414,28 @@ static bool is_sync_callback_calling_kfunc(u32 btf_id)
return btf_id == special_kfunc_list[KF_bpf_rbtree_add_impl];
}
+static bool is_async_callback_calling_kfunc(u32 btf_id)
+{
+ return btf_id == special_kfunc_list[KF_bpf_wq_set_callback_impl];
+}
+
static bool is_bpf_throw_kfunc(struct bpf_insn *insn)
{
return bpf_pseudo_kfunc_call(insn) && insn->off == 0 &&
insn->imm == special_kfunc_list[KF_bpf_throw];
}
+static bool is_bpf_wq_set_callback_impl_kfunc(u32 btf_id)
+{
+ return btf_id == special_kfunc_list[KF_bpf_wq_set_callback_impl];
+}
+
+static bool is_callback_calling_kfunc(u32 btf_id)
+{
+ return is_sync_callback_calling_kfunc(btf_id) ||
+ is_async_callback_calling_kfunc(btf_id);
+}
+
static bool is_rbtree_lock_required_kfunc(u32 btf_id)
{
return is_bpf_rbtree_api_kfunc(btf_id);
@@ -12219,6 +12247,16 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
}
}
+ if (is_bpf_wq_set_callback_impl_kfunc(meta.func_id)) {
+ err = push_callback_call(env, insn, insn_idx, meta.subprogno,
+ set_timer_callback_state);
+ if (err) {
+ verbose(env, "kfunc %s#%d failed callback verification\n",
+ func_name, meta.func_id);
+ return err;
+ }
+ }
+
rcu_lock = is_kfunc_bpf_rcu_read_lock(&meta);
rcu_unlock = is_kfunc_bpf_rcu_read_unlock(&meta);
@@ -16982,6 +17020,9 @@ static bool states_equal(struct bpf_verifier_env *env,
if (old->active_rcu_lock != cur->active_rcu_lock)
return false;
+ if (old->in_sleepable != cur->in_sleepable)
+ return false;
+
/* for states to be equal callsites have to be the same
* and all frame states need to be equivalent
*/
@@ -19653,6 +19694,28 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
desc->func_id == special_kfunc_list[KF_bpf_rdonly_cast]) {
insn_buf[0] = BPF_MOV64_REG(BPF_REG_0, BPF_REG_1);
*cnt = 1;
+ } else if (is_bpf_wq_set_callback_impl_kfunc(desc->func_id)) {
+ /* The verifier will process callback_fn as many times as necessary
+ * with different maps and the register states prepared by
+ * set_timer_callback_state will be accurate.
+ *
+ * The following use case is valid:
+ * map1 is shared by prog1, prog2, prog3.
+ * prog1 calls bpf_timer_init for some map1 elements
+ * prog2 calls bpf_timer_set_callback for some map1 elements.
+ * Those that were not bpf_timer_init-ed will return -EINVAL.
+ * prog3 calls bpf_timer_start for some map1 elements.
+ * Those that were not both bpf_timer_init-ed and
+ * bpf_timer_set_callback-ed will return -EINVAL.
+ */
+ struct bpf_insn ld_addrs[2] = {
+ BPF_LD_IMM64(BPF_REG_4, (long)env->prog->aux),
+ };
+
+ insn_buf[0] = ld_addrs[0];
+ insn_buf[1] = ld_addrs[1];
+ insn_buf[2] = *insn;
+ *cnt = 3;
}
return 0;
}
--
2.44.0
