On Feb 14 2024, Benjamin Tissoires wrote:
> They are implemented as a kfunc, which means a little bit of tweaks in
> the verifier.
>
> Signed-off-by: Benjamin Tissoires <bentiss@xxxxxxxxxx>
>
> ---
>
> changes in v2 (compared to the one attaches to v1 0/9):
> - make use of a kfunc
> - add a (non-used) BPF_F_TIMER_SLEEPABLE
> - the callback is *not* called, it makes the kernel crashes
> ---
> include/linux/bpf_verifier.h | 2 +
> include/uapi/linux/bpf.h | 12 +++++
> kernel/bpf/helpers.c | 105 ++++++++++++++++++++++++++++++++++++++++---
> kernel/bpf/verifier.c | 72 ++++++++++++++++++++++++++---
> 4 files changed, 180 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> index 84365e6dd85d..789ef5fec547 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;
> @@ -626,6 +627,7 @@ struct bpf_subprog_info {
> bool is_async_cb: 1;
> bool is_exception_cb: 1;
> bool args_cached: 1;
> + bool is_sleepable: 1;
>
> u8 arg_cnt;
> struct bpf_subprog_arg_info args[MAX_BPF_FUNC_REG_ARGS];
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index d96708380e52..0838597028a9 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -7427,6 +7427,18 @@ enum {
> BPF_F_TIMER_CPU_PIN = (1ULL << 1),
> };
>
> +/* Extra flags to control bpf_timer_init() behaviour, in addition to CLOCK_*.
> + * - BPF_F_TIMER_SLEEPABLE: Timer will run in a workqueue in a sleepable
> + * context.
> + */
> +enum {
> + /* CLOCK_* are using bits 0 to 3 */
> + BPF_F_TIMER_SLEEPABLE = (1ULL << 4),
> + __MAX_BPF_F_TIMER_INIT,
> +};
> +
> +#define MAX_BPF_F_TIMER_INIT __MAX_BPF_F_TIMER_INIT
> +
> /* BPF numbers iterator state */
> struct bpf_iter_num {
> /* opaque iterator state; having __u64 here allows to preserve correct
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index 4db1c658254c..2dbc09ce841a 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -1097,9 +1097,11 @@ const struct bpf_func_proto bpf_snprintf_proto = {
> */
> struct bpf_hrtimer {
> struct hrtimer timer;
> + struct work_struct work;
> struct bpf_map *map;
> struct bpf_prog *prog;
> void __rcu *callback_fn;
> + void __rcu *sleepable_cb_fn;
> void *value;
> };
>
> @@ -1113,18 +1115,59 @@ struct bpf_timer_kern {
> struct bpf_spin_lock lock;
> } __attribute__((aligned(8)));
>
> +static void bpf_timer_work_cb(struct work_struct *work)
> +{
> + struct bpf_hrtimer *t = container_of(work, struct bpf_hrtimer, work);
> + struct bpf_map *map = t->map;
> + void *value = t->value;
> + bpf_callback_t callback_fn;
> + void *key;
> + u32 idx;
> +
> + BTF_TYPE_EMIT(struct bpf_timer);
> +
> + rcu_read_lock();
> + callback_fn = rcu_dereference(t->sleepable_cb_fn);
> + rcu_read_unlock();
> + if (!callback_fn)
> + return;
> +
> + /* FIXME: do we need any locking? */
> + if (map->map_type == BPF_MAP_TYPE_ARRAY) {
> + struct bpf_array *array = container_of(map, struct bpf_array, map);
> +
> + /* compute the key */
> + idx = ((char *)value - array->value) / array->elem_size;
> + key = &idx;
> + } else { /* hash or lru */
> + key = value - round_up(map->key_size, 8);
> + }
> +
> + /* FIXME: this crashes the system with
> + * BUG: kernel NULL pointer dereference, address: 000000000000000b
> + */
> + /* callback_fn((u64)(long)map, (u64)(long)key, (u64)(long)value, 0, 0); */
I've found an interesting side effect here.
If I uncomment the line above, I get the following dumpstack:
[ 5.375257] BUG: kernel NULL pointer dereference, address: 000000000000000b
[ 5.376587] #PF: supervisor instruction fetch in kernel mode
[ 5.376932] #PF: error_code(0x0010) - not-present page
[ 5.377249] PGD 1016e6067 P4D 1016e6067 PUD 1016e5067 PMD 0
[ 5.377602] Oops: 0010 [#1] PREEMPT SMP NOPTI
[ 5.377876] CPU: 0 PID: 10 Comm: kworker/0:1 Not tainted 6.8.0-rc2-gd2c1e1837606-dirty #285
[ 5.378378] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-1.fc39 04/01/2014
[ 5.378913] Workqueue: events bpf_timer_work_cb
[ 5.379197] RIP: 0010:0xb
[ 5.379369] Code: Unable to access opcode bytes at 0xffffffffffffffe1.
[ 5.379768] RSP: 0018:ffffa5300005be10 EFLAGS: 00010246
[ 5.380088] RAX: 0000000000000068 RBX: 000000000000000b RCX: 0000000000000000
[ 5.380523] RDX: ffffa530012a5ff0 RSI: ffffa530012a5fe8 RDI: ffff915ec2bad000
[ 5.380947] RBP: ffff915ec2bad000 R08: 0000000000000000 R09: 0000000000000001
[ 5.381368] R10: 0000000000000000 R11: ffffffff9166f820 R12: ffffa530012a5ff0
[ 5.381793] R13: ffffa530012a5fe8 R14: ffff915ec0073005 R15: ffffffff900aea8a
[ 5.382213] FS: 0000000000000000(0000) GS:ffff915efbc00000(0000) knlGS:0000000000000000
[ 5.382691] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 5.383036] CR2: ffffffffffffffe1 CR3: 000000010761e003 CR4: 0000000000770ef0
[ 5.383460] PKRU: 55555554
[ 5.383643] Call Trace:
[ 5.383831] <TASK>
[ 5.383994] ? __die+0x23/0x70
[ 5.384228] ? page_fault_oops+0x181/0x4a0
[ 5.384541] ? exc_page_fault+0x67/0x1a0
[ 5.384840] ? asm_exc_page_fault+0x26/0x30
[ 5.385154] ? process_one_work+0x16a/0x4b0
[ 5.385467] ? bpf_timer_work_cb+0xfc/0x240
[ 5.385789] ? process_one_work+0x1d4/0x4b0
[ 5.386101] ? worker_thread+0x1d5/0x3c0
[ 5.386393] ? __pfx_worker_thread+0x10/0x10
[ 5.386724] ? kthread+0xf5/0x130
[ 5.386974] ? __pfx_kthread+0x10/0x10
[ 5.387255] ? ret_from_fork+0x31/0x50
[ 5.387537] ? __pfx_kthread+0x10/0x10
[ 5.387820] ? ret_from_fork_asm+0x1b/0x30
[ 5.388127] </TASK>
And it looks like the callback is properly called, but the fault comes
after:
(gdb) list *(process_one_work+0x16a)
0xffffffff810aea8a is in process_one_work (kernel/workqueue.c:2606).
2601 * disabled.
2602 */
2603 set_work_pool_and_clear_pending(work, pool->id);
2604
2605 pwq->stats[PWQ_STAT_STARTED]++;
2606 raw_spin_unlock_irq(&pool->lock);
2607
2608 lock_map_acquire(&pwq->wq->lockdep_map);
2609 lock_map_acquire(&lockdep_map);
2610 /*
And there is no real reason for the spinlock to not be set unless there
is a memroy corruption.
And if in my program I call bpf_timer_set_callback() before bpf_timer_set_sleepable_cb()
like:
bpf_timer_set_callback(timer, timer_cb1);
bpf_timer_set_sleepable_cb(timer, timer_cb1);
I do not see the corruption in the memory.
So it seems that when BPF calls the helper, the callback_fn is set in a
mode that it is not polluting the memory, while when calling the function
pointer from a kfunc, something is not properly set and there is a
memory corruption.
Does that rings any bell?
> + /* The verifier checked that return value is zero. */
> +}
> +
> static DEFINE_PER_CPU(struct bpf_hrtimer *, hrtimer_running);
>
> static enum hrtimer_restart bpf_timer_cb(struct hrtimer *hrtimer)
> {
> struct bpf_hrtimer *t = container_of(hrtimer, struct bpf_hrtimer, timer);
> + bpf_callback_t callback_fn, sleepable_cb_fn;
> struct bpf_map *map = t->map;
> void *value = t->value;
> - bpf_callback_t callback_fn;
> void *key;
> u32 idx;
>
> BTF_TYPE_EMIT(struct bpf_timer);
> + sleepable_cb_fn = rcu_dereference_check(t->sleepable_cb_fn, rcu_read_lock_bh_held());
> + if (sleepable_cb_fn) {
> + schedule_work(&t->work);
> + goto out;
> + }
> +
> callback_fn = rcu_dereference_check(t->callback_fn, rcu_read_lock_bh_held());
> if (!callback_fn)
> goto out;
> @@ -1154,10 +1197,14 @@ static enum hrtimer_restart bpf_timer_cb(struct hrtimer *hrtimer)
> return HRTIMER_NORESTART;
> }
>
> +#define BPF_TIMER_CLOCK_MASK (MAX_CLOCKS - 1) /* 0xf */
> +#define BPF_TIMER_FLAGS_MASK GENMASK_ULL(63, 4)
> +
> BPF_CALL_3(bpf_timer_init, struct bpf_timer_kern *, timer, struct bpf_map *, map,
> u64, flags)
> {
> - clockid_t clockid = flags & (MAX_CLOCKS - 1);
> + clockid_t clockid = flags & BPF_TIMER_CLOCK_MASK;
> + u64 bpf_timer_flags = flags & BPF_TIMER_FLAGS_MASK;
> struct bpf_hrtimer *t;
> int ret = 0;
>
> @@ -1168,7 +1215,7 @@ BPF_CALL_3(bpf_timer_init, struct bpf_timer_kern *, timer, struct bpf_map *, map
> if (in_nmi())
> return -EOPNOTSUPP;
>
> - if (flags >= MAX_CLOCKS ||
> + if (bpf_timer_flags & ~(BPF_F_TIMER_SLEEPABLE) ||
> /* similar to timerfd except _ALARM variants are not supported */
> (clockid != CLOCK_MONOTONIC &&
> clockid != CLOCK_REALTIME &&
> @@ -1190,7 +1237,10 @@ BPF_CALL_3(bpf_timer_init, struct bpf_timer_kern *, timer, struct bpf_map *, map
> t->map = map;
> t->prog = NULL;
> rcu_assign_pointer(t->callback_fn, NULL);
> + rcu_assign_pointer(t->sleepable_cb_fn, NULL);
> + /* FIXME: probably do something about the SLEEPABLE flag */
> hrtimer_init(&t->timer, clockid, HRTIMER_MODE_REL_SOFT);
> + INIT_WORK(&t->work, bpf_timer_work_cb);
> t->timer.function = bpf_timer_cb;
> WRITE_ONCE(timer->timer, t);
> /* Guarantee the order between timer->timer and map->usercnt. So
> @@ -1221,8 +1271,8 @@ static const struct bpf_func_proto bpf_timer_init_proto = {
> .arg3_type = ARG_ANYTHING,
> };
>
> -BPF_CALL_3(bpf_timer_set_callback, struct bpf_timer_kern *, timer, void *, callback_fn,
> - struct bpf_prog_aux *, aux)
> +static int __bpf_timer_set_callback(struct bpf_timer_kern *timer, void *callback_fn,
> + struct bpf_prog_aux *aux, bool is_sleepable)
> {
> struct bpf_prog *prev, *prog = aux->prog;
> struct bpf_hrtimer *t;
> @@ -1260,12 +1310,24 @@ BPF_CALL_3(bpf_timer_set_callback, struct bpf_timer_kern *, timer, void *, callb
> bpf_prog_put(prev);
> t->prog = prog;
> }
> - rcu_assign_pointer(t->callback_fn, callback_fn);
> + if (is_sleepable) {
> + rcu_assign_pointer(t->sleepable_cb_fn, callback_fn);
> + rcu_assign_pointer(t->callback_fn, NULL);
> + } else {
> + rcu_assign_pointer(t->callback_fn, callback_fn);
> + rcu_assign_pointer(t->sleepable_cb_fn, NULL);
> + }
> out:
> __bpf_spin_unlock_irqrestore(&timer->lock);
> return ret;
> }
>
> +BPF_CALL_3(bpf_timer_set_callback, struct bpf_timer_kern *, timer, void *, callback_fn,
> + struct bpf_prog_aux *, aux)
> +{
> + return __bpf_timer_set_callback(timer, callback_fn, aux, false);
> +}
> +
> static const struct bpf_func_proto bpf_timer_set_callback_proto = {
> .func = bpf_timer_set_callback,
> .gpl_only = true,
> @@ -1353,6 +1415,7 @@ BPF_CALL_1(bpf_timer_cancel, struct bpf_timer_kern *, timer)
> * if it was running.
> */
> ret = ret ?: hrtimer_cancel(&t->timer);
> + ret = ret ?: cancel_work_sync(&t->work);
> return ret;
> }
>
> @@ -1407,6 +1470,8 @@ void bpf_timer_cancel_and_free(void *val)
> */
> if (this_cpu_read(hrtimer_running) != t)
> hrtimer_cancel(&t->timer);
> +
> + cancel_work_sync(&t->work);
> kfree(t);
> }
>
> @@ -2542,6 +2607,33 @@ __bpf_kfunc void bpf_throw(u64 cookie)
> WARN(1, "A call to BPF exception callback should never return\n");
> }
>
> +/* FIXME: use kernel doc style */
> +/* Description
> + * Configure the timer to call *callback_fn* static function in a
> + * sleepable context.
> + * Return
> + * 0 on success.
> + * **-EINVAL** if *timer* was not initialized with bpf_timer_init() earlier.
> + * **-EPERM** if *timer* is in a map that doesn't have any user references.
> + * The user space should either hold a file descriptor to a map with timers
> + * or pin such map in bpffs. When map is unpinned or file descriptor is
> + * closed all timers in the map will be cancelled and freed.
> + */
> +__bpf_kfunc int bpf_timer_set_sleepable_cb(struct bpf_timer_kern *timer,
> + int (callback_fn)(void *map, int *key, struct bpf_timer *timer))
> +{
> + struct bpf_throw_ctx ctx = {};
> +
> + /* FIXME: definietely not sure this is OK */
> + arch_bpf_stack_walk(bpf_stack_walker, &ctx);
> + WARN_ON_ONCE(!ctx.aux);
> +
> + if (!ctx.aux)
> + return -EINVAL;
> +
> + return __bpf_timer_set_callback(timer, (void *)callback_fn, ctx.aux, true);
> +}
> +
> __bpf_kfunc_end_defs();
>
> BTF_KFUNCS_START(generic_btf_ids)
> @@ -2573,6 +2665,7 @@ BTF_ID_FLAGS(func, bpf_task_get_cgroup1, KF_ACQUIRE | KF_RCU | KF_RET_NULL)
> #endif
> BTF_ID_FLAGS(func, bpf_task_from_pid, KF_ACQUIRE | KF_RET_NULL)
> BTF_ID_FLAGS(func, bpf_throw)
> +BTF_ID_FLAGS(func, bpf_timer_set_sleepable_cb)
I also just realized that this should go into common_btf_ids so that
anybody can use it, not just tracing.
Cheers,
Benjamin
> BTF_KFUNCS_END(generic_btf_ids)
>
> static const struct btf_kfunc_id_set generic_kfunc_set = {
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 7831adba9abf..67da3f7bddb5 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -503,6 +503,8 @@ 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_bpf_throw_kfunc(struct bpf_insn *insn);
>
> +static bool is_bpf_timer_set_sleepable_cb_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 ||
> @@ -513,7 +515,8 @@ static bool is_sync_callback_calling_function(enum bpf_func_id func_id)
>
> static bool is_async_callback_calling_function(enum bpf_func_id func_id)
> {
> - return func_id == BPF_FUNC_timer_set_callback;
> + return func_id == BPF_FUNC_timer_set_callback ||
> + is_bpf_timer_set_sleepable_cb_kfunc(func_id);
> }
>
> static bool is_callback_calling_function(enum bpf_func_id func_id)
> @@ -1414,6 +1417,7 @@ 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;
> @@ -2413,6 +2417,7 @@ 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 = env->subprog_info[subprog].is_sleepable;
> frame = kzalloc(sizeof(*frame), GFP_KERNEL);
> if (!frame)
> goto err;
> @@ -5257,7 +5262,8 @@ static int map_kptr_match_type(struct bpf_verifier_env *env,
>
> static bool in_sleepable(struct bpf_verifier_env *env)
> {
> - return env->prog->aux->sleepable;
> + return env->prog->aux->sleepable ||
> + (env->cur_state && env->cur_state->in_sleepable);
> }
>
> /* The non-sleepable programs and sleepable programs with explicit bpf_rcu_read_lock()
> @@ -5439,6 +5445,26 @@ static int check_map_access(struct bpf_verifier_env *env, u32 regno,
> return -EACCES;
> }
> break;
> + case BPF_TIMER:
> + /* FIXME: kptr does the above, should we use the same? */
> + if (src != ACCESS_DIRECT) {
> + verbose(env, "bpf_timer cannot be accessed indirectly by helper\n");
> + return -EACCES;
> + }
> + if (!tnum_is_const(reg->var_off)) {
> + verbose(env, "bpf_timer access cannot have variable offset\n");
> + return -EACCES;
> + }
> + if (p != off + reg->var_off.value) {
> + verbose(env, "bpf_timer access misaligned expected=%u off=%llu\n",
> + p, off + reg->var_off.value);
> + return -EACCES;
> + }
> + if (size != bpf_size_to_bytes(BPF_DW)) {
> + verbose(env, "bpf_timer access size must be BPF_DW\n");
> + return -EACCES;
> + }
> + break;
> default:
> verbose(env, "%s cannot be accessed directly by load/store\n",
> btf_field_type_name(field->type));
> @@ -9439,11 +9465,13 @@ static int push_callback_call(struct bpf_verifier_env *env, struct bpf_insn *ins
>
> if (insn->code == (BPF_JMP | BPF_CALL) &&
> insn->src_reg == 0 &&
> - insn->imm == BPF_FUNC_timer_set_callback) {
> + (insn->imm == BPF_FUNC_timer_set_callback ||
> + is_bpf_timer_set_sleepable_cb_kfunc(insn->imm))) {
> struct bpf_verifier_state *async_cb;
>
> /* there is no real recursion here. timer callbacks are async */
> env->subprog_info[subprog].is_async_cb = true;
> + env->subprog_info[subprog].is_sleepable = is_bpf_timer_set_sleepable_cb_kfunc(insn->imm);
> async_cb = push_async_cb(env, env->subprog_info[subprog].start,
> insn_idx, subprog);
> if (!async_cb)
> @@ -10412,6 +10440,10 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
> break;
> }
>
> + if (is_bpf_timer_set_sleepable_cb_kfunc(func_id))
> + err = push_callback_call(env, insn, insn_idx, meta.subprogno,
> + set_timer_callback_state);
> +
> if (err)
> return err;
>
> @@ -10789,6 +10821,7 @@ enum {
> KF_ARG_LIST_NODE_ID,
> KF_ARG_RB_ROOT_ID,
> KF_ARG_RB_NODE_ID,
> + KF_ARG_TIMER_ID,
> };
>
> BTF_ID_LIST(kf_arg_btf_ids)
> @@ -10797,6 +10830,7 @@ BTF_ID(struct, bpf_list_head)
> BTF_ID(struct, bpf_list_node)
> BTF_ID(struct, bpf_rb_root)
> BTF_ID(struct, bpf_rb_node)
> +BTF_ID(struct, bpf_timer_kern)
>
> static bool __is_kfunc_ptr_arg_type(const struct btf *btf,
> const struct btf_param *arg, int type)
> @@ -10840,6 +10874,12 @@ static bool is_kfunc_arg_rbtree_node(const struct btf *btf, const struct btf_par
> return __is_kfunc_ptr_arg_type(btf, arg, KF_ARG_RB_NODE_ID);
> }
>
> +static bool is_kfunc_arg_timer(const struct btf *btf, const struct btf_param *arg)
> +{
> + bool ret = __is_kfunc_ptr_arg_type(btf, arg, KF_ARG_TIMER_ID);
> + return ret;
> +}
> +
> static bool is_kfunc_arg_callback(struct bpf_verifier_env *env, const struct btf *btf,
> const struct btf_param *arg)
> {
> @@ -10908,6 +10948,7 @@ enum kfunc_ptr_arg_type {
> KF_ARG_PTR_TO_RB_NODE,
> KF_ARG_PTR_TO_NULL,
> KF_ARG_PTR_TO_CONST_STR,
> + KF_ARG_PTR_TO_TIMER,
> };
>
> enum special_kfunc_type {
> @@ -10934,6 +10975,7 @@ enum special_kfunc_type {
> KF_bpf_percpu_obj_drop_impl,
> KF_bpf_throw,
> KF_bpf_iter_css_task_new,
> + KF_bpf_timer_set_sleepable_cb,
> };
>
> BTF_SET_START(special_kfunc_set)
> @@ -10960,6 +11002,7 @@ BTF_ID(func, bpf_throw)
> #ifdef CONFIG_CGROUPS
> BTF_ID(func, bpf_iter_css_task_new)
> #endif
> +BTF_ID(func, bpf_timer_set_sleepable_cb)
> BTF_SET_END(special_kfunc_set)
>
> BTF_ID_LIST(special_kfunc_list)
> @@ -10990,6 +11033,7 @@ BTF_ID(func, bpf_iter_css_task_new)
> #else
> BTF_ID_UNUSED
> #endif
> +BTF_ID(func, bpf_timer_set_sleepable_cb)
>
> static bool is_kfunc_ret_null(struct bpf_kfunc_call_arg_meta *meta)
> {
> @@ -11061,6 +11105,9 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
> if (is_kfunc_arg_const_str(meta->btf, &args[argno]))
> return KF_ARG_PTR_TO_CONST_STR;
>
> + if (is_kfunc_arg_timer(meta->btf, &args[argno]))
> + return KF_ARG_PTR_TO_TIMER;
> +
> if ((base_type(reg->type) == PTR_TO_BTF_ID || reg2btf_ids[base_type(reg->type)])) {
> if (!btf_type_is_struct(ref_t)) {
> verbose(env, "kernel function %s args#%d pointer type %s %s is not supported\n",
> @@ -11318,6 +11365,11 @@ static bool is_bpf_throw_kfunc(struct bpf_insn *insn)
> insn->imm == special_kfunc_list[KF_bpf_throw];
> }
>
> +static bool is_bpf_timer_set_sleepable_cb_kfunc(u32 btf_id)
> +{
> + return btf_id == special_kfunc_list[KF_bpf_timer_set_sleepable_cb];
> +}
> +
> static bool is_rbtree_lock_required_kfunc(u32 btf_id)
> {
> return is_bpf_rbtree_api_kfunc(btf_id);
> @@ -11693,6 +11745,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
> case KF_ARG_PTR_TO_CALLBACK:
> case KF_ARG_PTR_TO_REFCOUNTED_KPTR:
> case KF_ARG_PTR_TO_CONST_STR:
> + case KF_ARG_PTR_TO_TIMER:
> /* Trusted by default */
> break;
> default:
> @@ -11973,6 +12026,9 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
> if (ret)
> return ret;
> break;
> + case KF_ARG_PTR_TO_TIMER:
> + /* FIXME: should we do anything here? */
> + break;
> }
> }
>
> @@ -15591,7 +15647,9 @@ static int visit_insn(int t, struct bpf_verifier_env *env)
> return DONE_EXPLORING;
>
> case BPF_CALL:
> - if (insn->src_reg == 0 && insn->imm == BPF_FUNC_timer_set_callback)
> + if (insn->src_reg == 0 &&
> + (insn->imm == BPF_FUNC_timer_set_callback ||
> + is_bpf_timer_set_sleepable_cb_kfunc(insn->imm)))
> /* Mark this call insn as a prune point to trigger
> * is_state_visited() check before call itself is
> * processed by __check_func_call(). Otherwise new
> @@ -16767,6 +16825,9 @@ 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
> */
> @@ -19644,7 +19705,8 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
> continue;
> }
>
> - if (insn->imm == BPF_FUNC_timer_set_callback) {
> + if (insn->imm == BPF_FUNC_timer_set_callback ||
> + is_bpf_timer_set_sleepable_cb_kfunc(insn->imm)) {
> /* 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.
>
> --
> 2.43.0
>
