diff options
| author | Alexei Starovoitov <ast@kernel.org> | 2025-09-23 07:34:39 -0700 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2025-09-23 07:34:40 -0700 |
| commit | 348f6117c16ae89a06f53ec6dc893bd7b7a724b4 (patch) | |
| tree | 5711595f7d17ddd335f8f186720480a878b37870 /kernel/bpf | |
| parent | 58a5820582e4c809dd26b3f2d396cf072411d6e8 (diff) | |
| parent | c6ae18e0af5e7c809ac26350043924e062dbb76f (diff) | |
Merge branch 'bpf-introduce-deferred-task-context-execution'
Mykyta Yatsenko says:
====================
bpf: Introduce deferred task context execution
From: Mykyta Yatsenko <yatsenko@meta.com>
This patch introduces a new mechanism for BPF programs to schedule
deferred execution in the context of a specific task using the kernel’s
task_work infrastructure.
The new bpf_task_work interface enables BPF use cases that
require sleepable subprogram execution within task context, for example,
scheduling sleepable function from the context that does not
allow sleepable, such as NMI.
Introduced kfuncs bpf_task_work_schedule_signal() and
bpf_task_work_schedule_resume() for scheduling BPF callbacks correspond
to different modes used by task_work (TWA_SIGNAL or TWA_RESUME).
The implementation manages scheduling state via metadata objects (struct
bpf_task_work_context). Pointers to bpf_task_work_context are stored
in BPF map values. State transitions are handled via an atomic
state machine (bpf_task_work_state) to ensure correctness under
concurrent usage and deletion, lifetime is guarded by refcounting and
RCU Tasks Trace.
Kfuncs call task_work_add() indirectly via irq_work to avoid locking in
potentially NMI context.
Changelog:
---
v7 -> v8
v7: https://lore.kernel.org/bpf/20250922232611.614512-1-mykyta.yatsenko5@gmail.com/
* Fix unused variable warning in patch 1
* Decrease stress test time from 2 to 1 second
* Went through CI warnings, other than unused variable, there are just
2 new in kernel/bpf/helpers.c related to newly introduced kfuncs, these
look expected.
v6 -> v7
v6: https://lore.kernel.org/bpf/20250918132615.193388-1-mykyta.yatsenko5@gmail.com/
* Added stress test
* Extending refactoring in patch 1
* Changing comment and removing one check for map->usercnt in patch 7
v5 -> v6
v5: https://lore.kernel.org/bpf/20250916233651.258458-1-mykyta.yatsenko5@gmail.com/
* Fixing readability in verifier.c:check_map_field_pointer()
* Removing BUG_ON from helpers.c
v4 -> v5
v4:
https://lore.kernel.org/all/20250915201820.248977-1-mykyta.yatsenko5@gmail.com/
* Fix invalid/null pointer dereference bug, reported by syzbot
* Nits in selftests
v3 -> v4
v3: https://lore.kernel.org/all/20250905164508.1489482-1-mykyta.yatsenko5@gmail.com/
* Modify async callback return value processing in verifier, to allow
non-zero return values.
* Change return type of the callback from void to int, as verifier
expects scalar value.
* Switched to void* for bpf_map API kfunc arguments to avoid casts.
* Addressing numerous nits and small improvements.
v2 -> v3
v2: https://lore.kernel.org/all/20250815192156.272445-1-mykyta.yatsenko5@gmail.com/
* Introduce ref counting
* Add patches with minor verifier and btf.c refactorings to avoid code
duplication
* Rework initiation of the task work scheduling to handle race with map
usercnt dropping to zero
====================
Link: https://patch.msgid.link/20250923112404.668720-1-mykyta.yatsenko5@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/arraymap.c | 8 | ||||
| -rw-r--r-- | kernel/bpf/btf.c | 91 | ||||
| -rw-r--r-- | kernel/bpf/hashtab.c | 43 | ||||
| -rw-r--r-- | kernel/bpf/helpers.c | 358 | ||||
| -rw-r--r-- | kernel/bpf/syscall.c | 16 | ||||
| -rw-r--r-- | kernel/bpf/verifier.c | 169 |
6 files changed, 573 insertions, 112 deletions
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c index 26d5dda989bc..80b1765a3159 100644 --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -443,7 +443,7 @@ static void *array_map_vmalloc_addr(struct bpf_array *array) return (void *)round_down((unsigned long)array, PAGE_SIZE); } -static void array_map_free_timers_wq(struct bpf_map *map) +static void array_map_free_internal_structs(struct bpf_map *map) { struct bpf_array *array = container_of(map, struct bpf_array, map); int i; @@ -451,12 +451,14 @@ static void array_map_free_timers_wq(struct bpf_map *map) /* We don't reset or free fields other than timer and workqueue * on uref dropping to zero. */ - if (btf_record_has_field(map->record, BPF_TIMER | BPF_WORKQUEUE)) { + if (btf_record_has_field(map->record, BPF_TIMER | BPF_WORKQUEUE | BPF_TASK_WORK)) { for (i = 0; i < array->map.max_entries; i++) { if (btf_record_has_field(map->record, BPF_TIMER)) bpf_obj_free_timer(map->record, array_map_elem_ptr(array, i)); if (btf_record_has_field(map->record, BPF_WORKQUEUE)) bpf_obj_free_workqueue(map->record, array_map_elem_ptr(array, i)); + if (btf_record_has_field(map->record, BPF_TASK_WORK)) + bpf_obj_free_task_work(map->record, array_map_elem_ptr(array, i)); } } } @@ -795,7 +797,7 @@ const struct bpf_map_ops array_map_ops = { .map_alloc = array_map_alloc, .map_free = array_map_free, .map_get_next_key = array_map_get_next_key, - .map_release_uref = array_map_free_timers_wq, + .map_release_uref = array_map_free_internal_structs, .map_lookup_elem = array_map_lookup_elem, .map_update_elem = array_map_update_elem, .map_delete_elem = array_map_delete_elem, diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 64739308902f..9f47a3aa7ff8 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -3478,60 +3478,45 @@ btf_find_graph_root(const struct btf *btf, const struct btf_type *pt, return BTF_FIELD_FOUND; } -#define field_mask_test_name(field_type, field_type_str) \ - if (field_mask & field_type && !strcmp(name, field_type_str)) { \ - type = field_type; \ - goto end; \ - } - static int btf_get_field_type(const struct btf *btf, const struct btf_type *var_type, - u32 field_mask, u32 *seen_mask, - int *align, int *sz) -{ - int type = 0; + u32 field_mask, u32 *seen_mask, int *align, int *sz) +{ + const struct { + enum btf_field_type type; + const char *const name; + const bool is_unique; + } field_types[] = { + { BPF_SPIN_LOCK, "bpf_spin_lock", true }, + { BPF_RES_SPIN_LOCK, "bpf_res_spin_lock", true }, + { BPF_TIMER, "bpf_timer", true }, + { BPF_WORKQUEUE, "bpf_wq", true }, + { BPF_TASK_WORK, "bpf_task_work", true }, + { BPF_LIST_HEAD, "bpf_list_head", false }, + { BPF_LIST_NODE, "bpf_list_node", false }, + { BPF_RB_ROOT, "bpf_rb_root", false }, + { BPF_RB_NODE, "bpf_rb_node", false }, + { BPF_REFCOUNT, "bpf_refcount", false }, + }; + int type = 0, i; const char *name = __btf_name_by_offset(btf, var_type->name_off); - - if (field_mask & BPF_SPIN_LOCK) { - if (!strcmp(name, "bpf_spin_lock")) { - if (*seen_mask & BPF_SPIN_LOCK) - return -E2BIG; - *seen_mask |= BPF_SPIN_LOCK; - type = BPF_SPIN_LOCK; - goto end; - } - } - if (field_mask & BPF_RES_SPIN_LOCK) { - if (!strcmp(name, "bpf_res_spin_lock")) { - if (*seen_mask & BPF_RES_SPIN_LOCK) - return -E2BIG; - *seen_mask |= BPF_RES_SPIN_LOCK; - type = BPF_RES_SPIN_LOCK; - goto end; - } - } - if (field_mask & BPF_TIMER) { - if (!strcmp(name, "bpf_timer")) { - if (*seen_mask & BPF_TIMER) - return -E2BIG; - *seen_mask |= BPF_TIMER; - type = BPF_TIMER; - goto end; - } - } - if (field_mask & BPF_WORKQUEUE) { - if (!strcmp(name, "bpf_wq")) { - if (*seen_mask & BPF_WORKQUEUE) + const char *field_type_name; + enum btf_field_type field_type; + bool is_unique; + + for (i = 0; i < ARRAY_SIZE(field_types); ++i) { + field_type = field_types[i].type; + field_type_name = field_types[i].name; + is_unique = field_types[i].is_unique; + if (!(field_mask & field_type) || strcmp(name, field_type_name)) + continue; + if (is_unique) { + if (*seen_mask & field_type) return -E2BIG; - *seen_mask |= BPF_WORKQUEUE; - type = BPF_WORKQUEUE; - goto end; + *seen_mask |= field_type; } + type = field_type; + goto end; } - field_mask_test_name(BPF_LIST_HEAD, "bpf_list_head"); - field_mask_test_name(BPF_LIST_NODE, "bpf_list_node"); - field_mask_test_name(BPF_RB_ROOT, "bpf_rb_root"); - field_mask_test_name(BPF_RB_NODE, "bpf_rb_node"); - field_mask_test_name(BPF_REFCOUNT, "bpf_refcount"); /* Only return BPF_KPTR when all other types with matchable names fail */ if (field_mask & (BPF_KPTR | BPF_UPTR) && !__btf_type_is_struct(var_type)) { @@ -3545,8 +3530,6 @@ end: return type; } -#undef field_mask_test_name - /* Repeat a number of fields for a specified number of times. * * Copy the fields starting from the first field and repeat them for @@ -3693,6 +3676,7 @@ static int btf_find_field_one(const struct btf *btf, case BPF_LIST_NODE: case BPF_RB_NODE: case BPF_REFCOUNT: + case BPF_TASK_WORK: ret = btf_find_struct(btf, var_type, off, sz, field_type, info_cnt ? &info[0] : &tmp); if (ret < 0) @@ -3985,6 +3969,7 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type rec->timer_off = -EINVAL; rec->wq_off = -EINVAL; rec->refcount_off = -EINVAL; + rec->task_work_off = -EINVAL; for (i = 0; i < cnt; i++) { field_type_size = btf_field_type_size(info_arr[i].type); if (info_arr[i].off + field_type_size > value_size) { @@ -4024,6 +4009,10 @@ struct btf_record *btf_parse_fields(const struct btf *btf, const struct btf_type /* Cache offset for faster lookup at runtime */ rec->wq_off = rec->fields[i].offset; break; + case BPF_TASK_WORK: + WARN_ON_ONCE(rec->task_work_off >= 0); + rec->task_work_off = rec->fields[i].offset; + break; case BPF_REFCOUNT: WARN_ON_ONCE(rec->refcount_off >= 0); /* Cache offset for faster lookup at runtime */ diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index 71f9931ac64c..c2fcd0cd51e5 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -215,7 +215,20 @@ static bool htab_has_extra_elems(struct bpf_htab *htab) return !htab_is_percpu(htab) && !htab_is_lru(htab) && !is_fd_htab(htab); } -static void htab_free_prealloced_timers_and_wq(struct bpf_htab *htab) +static void htab_free_internal_structs(struct bpf_htab *htab, struct htab_elem *elem) +{ + if (btf_record_has_field(htab->map.record, BPF_TIMER)) + bpf_obj_free_timer(htab->map.record, + htab_elem_value(elem, htab->map.key_size)); + if (btf_record_has_field(htab->map.record, BPF_WORKQUEUE)) + bpf_obj_free_workqueue(htab->map.record, + htab_elem_value(elem, htab->map.key_size)); + if (btf_record_has_field(htab->map.record, BPF_TASK_WORK)) + bpf_obj_free_task_work(htab->map.record, + htab_elem_value(elem, htab->map.key_size)); +} + +static void htab_free_prealloced_internal_structs(struct bpf_htab *htab) { u32 num_entries = htab->map.max_entries; int i; @@ -227,12 +240,7 @@ static void htab_free_prealloced_timers_and_wq(struct bpf_htab *htab) struct htab_elem *elem; elem = get_htab_elem(htab, i); - if (btf_record_has_field(htab->map.record, BPF_TIMER)) - bpf_obj_free_timer(htab->map.record, - htab_elem_value(elem, htab->map.key_size)); - if (btf_record_has_field(htab->map.record, BPF_WORKQUEUE)) - bpf_obj_free_workqueue(htab->map.record, - htab_elem_value(elem, htab->map.key_size)); + htab_free_internal_structs(htab, elem); cond_resched(); } } @@ -1490,7 +1498,7 @@ static void delete_all_elements(struct bpf_htab *htab) } } -static void htab_free_malloced_timers_and_wq(struct bpf_htab *htab) +static void htab_free_malloced_internal_structs(struct bpf_htab *htab) { int i; @@ -1502,28 +1510,23 @@ static void htab_free_malloced_timers_and_wq(struct bpf_htab *htab) hlist_nulls_for_each_entry(l, n, head, hash_node) { /* We only free timer on uref dropping to zero */ - if (btf_record_has_field(htab->map.record, BPF_TIMER)) - bpf_obj_free_timer(htab->map.record, - htab_elem_value(l, htab->map.key_size)); - if (btf_record_has_field(htab->map.record, BPF_WORKQUEUE)) - bpf_obj_free_workqueue(htab->map.record, - htab_elem_value(l, htab->map.key_size)); + htab_free_internal_structs(htab, l); } cond_resched_rcu(); } rcu_read_unlock(); } -static void htab_map_free_timers_and_wq(struct bpf_map *map) +static void htab_map_free_internal_structs(struct bpf_map *map) { struct bpf_htab *htab = container_of(map, struct bpf_htab, map); /* We only free timer and workqueue on uref dropping to zero */ - if (btf_record_has_field(htab->map.record, BPF_TIMER | BPF_WORKQUEUE)) { + if (btf_record_has_field(htab->map.record, BPF_TIMER | BPF_WORKQUEUE | BPF_TASK_WORK)) { if (!htab_is_prealloc(htab)) - htab_free_malloced_timers_and_wq(htab); + htab_free_malloced_internal_structs(htab); else - htab_free_prealloced_timers_and_wq(htab); + htab_free_prealloced_internal_structs(htab); } } @@ -2255,7 +2258,7 @@ const struct bpf_map_ops htab_map_ops = { .map_alloc = htab_map_alloc, .map_free = htab_map_free, .map_get_next_key = htab_map_get_next_key, - .map_release_uref = htab_map_free_timers_and_wq, + .map_release_uref = htab_map_free_internal_structs, .map_lookup_elem = htab_map_lookup_elem, .map_lookup_and_delete_elem = htab_map_lookup_and_delete_elem, .map_update_elem = htab_map_update_elem, @@ -2276,7 +2279,7 @@ const struct bpf_map_ops htab_lru_map_ops = { .map_alloc = htab_map_alloc, .map_free = htab_map_free, .map_get_next_key = htab_map_get_next_key, - .map_release_uref = htab_map_free_timers_and_wq, + .map_release_uref = htab_map_free_internal_structs, .map_lookup_elem = htab_lru_map_lookup_elem, .map_lookup_and_delete_elem = htab_lru_map_lookup_and_delete_elem, .map_lookup_elem_sys_only = htab_lru_map_lookup_elem_sys, diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 969f63f8ca28..c9fab9a356df 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -26,6 +26,8 @@ #include <linux/bpf_verifier.h> #include <linux/uaccess.h> #include <linux/verification.h> +#include <linux/task_work.h> +#include <linux/irq_work.h> #include "../../lib/kstrtox.h" @@ -1082,6 +1084,17 @@ const struct bpf_func_proto bpf_snprintf_proto = { .arg5_type = ARG_CONST_SIZE_OR_ZERO, }; +static void *map_key_from_value(struct bpf_map *map, void *value, u32 *arr_idx) +{ + if (map->map_type == BPF_MAP_TYPE_ARRAY) { + struct bpf_array *array = container_of(map, struct bpf_array, map); + + *arr_idx = ((char *)value - array->value) / array->elem_size; + return arr_idx; + } + return (void *)value - round_up(map->key_size, 8); +} + struct bpf_async_cb { struct bpf_map *map; struct bpf_prog *prog; @@ -1164,15 +1177,8 @@ static enum hrtimer_restart bpf_timer_cb(struct hrtimer *hrtimer) * bpf_map_delete_elem() on the same timer. */ this_cpu_write(hrtimer_running, t); - 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); - } + key = map_key_from_value(map, value, &idx); callback_fn((u64)(long)map, (u64)(long)key, (u64)(long)value, 0, 0); /* The verifier checked that return value is zero. */ @@ -1198,15 +1204,7 @@ static void bpf_wq_work(struct work_struct *work) if (!callback_fn) return; - 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); - } + key = map_key_from_value(map, value, &idx); rcu_read_lock_trace(); migrate_disable(); @@ -3906,8 +3904,332 @@ __bpf_kfunc int bpf_verify_pkcs7_signature(struct bpf_dynptr *data_p, } #endif /* CONFIG_KEYS */ +typedef int (*bpf_task_work_callback_t)(struct bpf_map *map, void *key, void *value); + +enum bpf_task_work_state { + /* bpf_task_work is ready to be used */ + BPF_TW_STANDBY = 0, + /* irq work scheduling in progress */ + BPF_TW_PENDING, + /* task work scheduling in progress */ + BPF_TW_SCHEDULING, + /* task work is scheduled successfully */ + BPF_TW_SCHEDULED, + /* callback is running */ + BPF_TW_RUNNING, + /* associated BPF map value is deleted */ + BPF_TW_FREED, +}; + +struct bpf_task_work_ctx { + enum bpf_task_work_state state; + refcount_t refcnt; + struct callback_head work; + struct irq_work irq_work; + /* bpf_prog that schedules task work */ + struct bpf_prog *prog; + /* task for which callback is scheduled */ + struct task_struct *task; + /* the map and map value associated with this context */ + struct bpf_map *map; + void *map_val; + enum task_work_notify_mode mode; + bpf_task_work_callback_t callback_fn; + struct rcu_head rcu; +} __aligned(8); + +/* Actual type for struct bpf_task_work */ +struct bpf_task_work_kern { + struct bpf_task_work_ctx *ctx; +}; + +static void bpf_task_work_ctx_reset(struct bpf_task_work_ctx *ctx) +{ + if (ctx->prog) { + bpf_prog_put(ctx->prog); + ctx->prog = NULL; + } + if (ctx->task) { + bpf_task_release(ctx->task); + ctx->task = NULL; + } +} + +static bool bpf_task_work_ctx_tryget(struct bpf_task_work_ctx *ctx) +{ + return refcount_inc_not_zero(&ctx->refcnt); +} + +static void bpf_task_work_ctx_put(struct bpf_task_work_ctx *ctx) +{ + if (!refcount_dec_and_test(&ctx->refcnt)) + return; + + bpf_task_work_ctx_reset(ctx); + + /* bpf_mem_free expects migration to be disabled */ + migrate_disable(); + bpf_mem_free(&bpf_global_ma, ctx); + migrate_enable(); +} + +static void bpf_task_work_cancel(struct bpf_task_work_ctx *ctx) +{ + /* + * Scheduled task_work callback holds ctx ref, so if we successfully + * cancelled, we put that ref on callback's behalf. If we couldn't + * cancel, callback will inevitably run or has already completed + * running, and it would have taken care of its ctx ref itself. + */ + if (task_work_cancel(ctx->task, &ctx->work)) + bpf_task_work_ctx_put(ctx); +} + +static void bpf_task_work_callback(struct callback_head *cb) +{ + struct bpf_task_work_ctx *ctx = container_of(cb, struct bpf_task_work_ctx, work); + enum bpf_task_work_state state; + u32 idx; + void *key; + + /* Read lock is needed to protect ctx and map key/value access */ + guard(rcu_tasks_trace)(); + /* + * This callback may start running before bpf_task_work_irq() switched to + * SCHEDULED state, so handle both transition variants SCHEDULING|SCHEDULED -> RUNNING. + */ + state = cmpxchg(&ctx->state, BPF_TW_SCHEDULING, BPF_TW_RUNNING); + if (state == BPF_TW_SCHEDULED) + state = cmpxchg(&ctx->state, BPF_TW_SCHEDULED, BPF_TW_RUNNING); + if (state == BPF_TW_FREED) { + bpf_task_work_ctx_put(ctx); + return; + } + + key = (void *)map_key_from_value(ctx->map, ctx->map_val, &idx); + + migrate_disable(); + ctx->callback_fn(ctx->map, key, ctx->map_val); + migrate_enable(); + + bpf_task_work_ctx_reset(ctx); + (void)cmpxchg(&ctx->state, BPF_TW_RUNNING, BPF_TW_STANDBY); + + bpf_task_work_ctx_put(ctx); +} + +static void bpf_task_work_irq(struct irq_work *irq_work) +{ + struct bpf_task_work_ctx *ctx = container_of(irq_work, struct bpf_task_work_ctx, irq_work); + enum bpf_task_work_state state; + int err; + + guard(rcu_tasks_trace)(); + + if (cmpxchg(&ctx->state, BPF_TW_PENDING, BPF_TW_SCHEDULING) != BPF_TW_PENDING) { + bpf_task_work_ctx_put(ctx); + return; + } + + err = task_work_add(ctx->task, &ctx->work, ctx->mode); + if (err) { + bpf_task_work_ctx_reset(ctx); + /* + * try to switch back to STANDBY for another task_work reuse, but we might have + * gone to FREED already, which is fine as we already cleaned up after ourselves + */ + (void)cmpxchg(&ctx->state, BPF_TW_SCHEDULING, BPF_TW_STANDBY); + bpf_task_work_ctx_put(ctx); + return; + } + + /* + * It's technically possible for just scheduled task_work callback to + * complete running by now, going SCHEDULING -> RUNNING and then + * dropping its ctx refcount. Instead of capturing extra ref just to + * protected below ctx->state access, we rely on RCU protection to + * perform below SCHEDULING -> SCHEDULED attempt. + */ + state = cmpxchg(&ctx->state, BPF_TW_SCHEDULING, BPF_TW_SCHEDULED); + if (state == BPF_TW_FREED) + bpf_task_work_cancel(ctx); /* clean up if we switched into FREED state */ +} + +static struct bpf_task_work_ctx *bpf_task_work_fetch_ctx(struct bpf_task_work *tw, + struct bpf_map *map) +{ + struct bpf_task_work_kern *twk = (void *)tw; + struct bpf_task_work_ctx *ctx, *old_ctx; + + ctx = READ_ONCE(twk->ctx); + if (ctx) + return ctx; + + ctx = bpf_mem_alloc(&bpf_global_ma, sizeof(struct bpf_task_work_ctx)); + if (!ctx) + return ERR_PTR(-ENOMEM); + + memset(ctx, 0, sizeof(*ctx)); + refcount_set(&ctx->refcnt, 1); /* map's own ref */ + ctx->state = BPF_TW_STANDBY; + + old_ctx = cmpxchg(&twk->ctx, NULL, ctx); + if (old_ctx) { + /* + * tw->ctx is set by concurrent BPF program, release allocated + * memory and try to reuse already set context. + */ + bpf_mem_free(&bpf_global_ma, ctx); + return old_ctx; + } + + return ctx; /* Success */ +} + +static struct bpf_task_work_ctx *bpf_task_work_acquire_ctx(struct bpf_task_work *tw, + struct bpf_map *map) +{ + struct bpf_task_work_ctx *ctx; + + ctx = bpf_task_work_fetch_ctx(tw, map); + if (IS_ERR(ctx)) + return ctx; + + /* try to get ref for task_work callback to hold */ + if (!bpf_task_work_ctx_tryget(ctx)) + return ERR_PTR(-EBUSY); + + if (cmpxchg(&ctx->state, BPF_TW_STANDBY, BPF_TW_PENDING) != BPF_TW_STANDBY) { + /* lost acquiring race or map_release_uref() stole it from us, put ref and bail */ + bpf_task_work_ctx_put(ctx); + return ERR_PTR(-EBUSY); + } + + /* + * If no process or bpffs is holding a reference to the map, no new callbacks should be + * scheduled. This does not address any race or correctness issue, but rather is a policy + * choice: dropping user references should stop everything. + */ + if (!atomic64_read(&map->usercnt)) { + /* drop ref we just got for task_work callback itself */ + bpf_task_work_ctx_put(ctx); + /* transfer map's ref into cancel_and_free() */ + bpf_task_work_cancel_and_free(tw); + return ERR_PTR(-EBUSY); + } + + return ctx; +} + +static int bpf_task_work_schedule(struct task_struct *task, struct bpf_task_work *tw, + struct bpf_map *map, bpf_task_work_callback_t callback_fn, + struct bpf_prog_aux *aux, enum task_work_notify_mode mode) +{ + struct bpf_prog *prog; + struct bpf_task_work_ctx *ctx; + int err; + + BTF_TYPE_EMIT(struct bpf_task_work); + + prog = bpf_prog_inc_not_zero(aux->prog); + if (IS_ERR(prog)) + return -EBADF; + task = bpf_task_acquire(task); + if (!task) { + err = -EBADF; + goto release_prog; + } + + ctx = bpf_task_work_acquire_ctx(tw, map); + if (IS_ERR(ctx)) { + err = PTR_ERR(ctx); + goto release_all; + } + + ctx->task = task; + ctx->callback_fn = callback_fn; + ctx->prog = prog; + ctx->mode = mode; + ctx->map = map; + ctx->map_val = (void *)tw - map->record->task_work_off; + init_task_work(&ctx->work, bpf_task_work_callback); + init_irq_work(&ctx->irq_work, bpf_task_work_irq); + + irq_work_queue(&ctx->irq_work); + return 0; + +release_all: + bpf_task_release(task); +release_prog: + bpf_prog_put(prog); + return err; +} + +/** + * bpf_task_work_schedule_signal - Schedule BPF callback using task_work_add with TWA_SIGNAL mode + * @task: Task struct for which callback should be scheduled + * @tw: Pointer to struct bpf_task_work in BPF map value for internal bookkeeping + * @map__map: bpf_map that embeds struct bpf_task_work in the values + * @callback: pointer to BPF subprogram to call + * @aux__prog: user should pass NULL + * + * Return: 0 if task work has been scheduled successfully, negative error code otherwise + */ +__bpf_kfunc int bpf_task_work_schedule_signal(struct task_struct *task, struct bpf_task_work *tw, + void *map__map, bpf_task_work_callback_t callback, + void *aux__prog) +{ + return bpf_task_work_schedule(task, tw, map__map, callback, aux__prog, TWA_SIGNAL); +} + +/** + * bpf_task_work_schedule_resume - Schedule BPF callback using task_work_add with TWA_RESUME mode + * @task: Task struct for which callback should be scheduled + * @tw: Pointer to struct bpf_task_work in BPF map value for internal bookkeeping + * @map__map: bpf_map that embeds struct bpf_task_work in the values + * @callback: pointer to BPF subprogram to call + * @aux__prog: user should pass NULL + * + * Return: 0 if task work has been scheduled successfully, negative error code otherwise + */ +__bpf_kfunc int bpf_task_work_schedule_resume(struct task_struct *task, struct bpf_task_work *tw, + void *map__map, bpf_task_work_callback_t callback, + void *aux__prog) +{ + return bpf_task_work_schedule(task, tw, map__map, callback, aux__prog, TWA_RESUME); +} + __bpf_kfunc_end_defs(); +static void bpf_task_work_cancel_scheduled(struct irq_work *irq_work) +{ + struct bpf_task_work_ctx *ctx = container_of(irq_work, struct bpf_task_work_ctx, irq_work); + + bpf_task_work_cancel(ctx); /* this might put task_work callback's ref */ + bpf_task_work_ctx_put(ctx); /* and here we put map's own ref that was transferred to us */ +} + +void bpf_task_work_cancel_and_free(void *val) +{ + struct bpf_task_work_kern *twk = val; + struct bpf_task_work_ctx *ctx; + enum bpf_task_work_state state; + + ctx = xchg(&twk->ctx, NULL); + if (!ctx) + return; + + state = xchg(&ctx->state, BPF_TW_FREED); + if (state == BPF_TW_SCHEDULED) { + /* run in irq_work to avoid locks in NMI */ + init_irq_work(&ctx->irq_work, bpf_task_work_cancel_scheduled); + irq_work_queue(&ctx->irq_work); + return; + } + + bpf_task_work_ctx_put(ctx); /* put bpf map's ref */ +} + BTF_KFUNCS_START(generic_btf_ids) #ifdef CONFIG_CRASH_DUMP BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE) @@ -4050,6 +4372,8 @@ BTF_ID_FLAGS(func, bpf_strnstr); BTF_ID_FLAGS(func, bpf_cgroup_read_xattr, KF_RCU) #endif BTF_ID_FLAGS(func, bpf_stream_vprintk, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_task_work_schedule_signal, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_task_work_schedule_resume, KF_TRUSTED_ARGS) BTF_KFUNCS_END(common_btf_ids) static const struct btf_kfunc_id_set common_kfunc_set = { diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 8a3c3d26f6e2..adb05d235011 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -674,6 +674,7 @@ void btf_record_free(struct btf_record *rec) case BPF_TIMER: case BPF_REFCOUNT: case BPF_WORKQUEUE: + case BPF_TASK_WORK: /* Nothing to release */ break; default: @@ -727,6 +728,7 @@ struct btf_record *btf_record_dup(const struct btf_record *rec) case BPF_TIMER: case BPF_REFCOUNT: case BPF_WORKQUEUE: + case BPF_TASK_WORK: /* Nothing to acquire */ break; default: @@ -785,6 +787,13 @@ void bpf_obj_free_workqueue(const struct btf_record *rec, void *obj) bpf_wq_cancel_and_free(obj + rec->wq_off); } +void bpf_obj_free_task_work(const struct btf_record *rec, void *obj) +{ + if (WARN_ON_ONCE(!btf_record_has_field(rec, BPF_TASK_WORK))) + return; + bpf_task_work_cancel_and_free(obj + rec->task_work_off); +} + void bpf_obj_free_fields(const struct btf_record *rec, void *obj) { const struct btf_field *fields; @@ -809,6 +818,9 @@ void bpf_obj_free_fields(const struct btf_record *rec, void *obj) case BPF_WORKQUEUE: bpf_wq_cancel_and_free(field_ptr); break; + case BPF_TASK_WORK: + bpf_task_work_cancel_and_free(field_ptr); + break; case BPF_KPTR_UNREF: WRITE_ONCE(*(u64 *)field_ptr, 0); break; @@ -1240,7 +1252,8 @@ static int map_check_btf(struct bpf_map *map, struct bpf_token *token, map->record = btf_parse_fields(btf, value_type, BPF_SPIN_LOCK | BPF_RES_SPIN_LOCK | BPF_TIMER | BPF_KPTR | BPF_LIST_HEAD | - BPF_RB_ROOT | BPF_REFCOUNT | BPF_WORKQUEUE | BPF_UPTR, + BPF_RB_ROOT | BPF_REFCOUNT | BPF_WORKQUEUE | BPF_UPTR | + BPF_TASK_WORK, map->value_size); if (!IS_ERR_OR_NULL(map->record)) { int i; @@ -1272,6 +1285,7 @@ static int map_check_btf(struct bpf_map *map, struct bpf_token *token, break; case BPF_TIMER: case BPF_WORKQUEUE: + case BPF_TASK_WORK: if (map->map_type != BPF_MAP_TYPE_HASH && map->map_type != BPF_MAP_TYPE_LRU_HASH && map->map_type != BPF_MAP_TYPE_ARRAY) { diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 1d4183bc3cd1..ceeb0ffe7d67 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2224,10 +2224,10 @@ static void mark_ptr_not_null_reg(struct bpf_reg_state *reg) /* transfer reg's id which is unique for every map_lookup_elem * as UID of the inner map. */ - if (btf_record_has_field(map->inner_map_meta->record, BPF_TIMER)) - reg->map_uid = reg->id; - if (btf_record_has_field(map->inner_map_meta->record, BPF_WORKQUEUE)) + if (btf_record_has_field(map->inner_map_meta->record, + BPF_TIMER | BPF_WORKQUEUE | BPF_TASK_WORK)) { reg->map_uid = reg->id; + } } else if (map->map_type == BPF_MAP_TYPE_XSKMAP) { reg->type = PTR_TO_XDP_SOCK; } else if (map->map_type == BPF_MAP_TYPE_SOCKMAP || @@ -8431,34 +8431,62 @@ static int process_spin_lock(struct bpf_verifier_env *env, int regno, int flags) return 0; } -static int process_timer_func(struct bpf_verifier_env *env, int regno, - struct bpf_call_arg_meta *meta) +/* Check if @regno is a pointer to a specific field in a map value */ +static int check_map_field_pointer(struct bpf_verifier_env *env, u32 regno, + enum btf_field_type field_type) { struct bpf_reg_state *regs = cur_regs(env), *reg = ®s[regno]; bool is_const = tnum_is_const(reg->var_off); struct bpf_map *map = reg->map_ptr; u64 val = reg->var_off.value; + const char *struct_name = btf_field_type_name(field_type); + int field_off = -1; if (!is_const) { verbose(env, - "R%d doesn't have constant offset. bpf_timer has to be at the constant offset\n", - regno); + "R%d doesn't have constant offset. %s has to be at the constant offset\n", + regno, struct_name); return -EINVAL; } if (!map->btf) { - verbose(env, "map '%s' has to have BTF in order to use bpf_timer\n", - map->name); + verbose(env, "map '%s' has to have BTF in order to use %s\n", map->name, + struct_name); return -EINVAL; } - if (!btf_record_has_field(map->record, BPF_TIMER)) { - verbose(env, "map '%s' has no valid bpf_timer\n", map->name); + if (!btf_record_has_field(map->record, field_type)) { + verbose(env, "map '%s' has no valid %s\n", map->name, struct_name); return -EINVAL; } - if (map->record->timer_off != val + reg->off) { - verbose(env, "off %lld doesn't point to 'struct bpf_timer' that is at %d\n", - val + reg->off, map->record->timer_off); + switch (field_type) { + case BPF_TIMER: + field_off = map->record->timer_off; + break; + case BPF_TASK_WORK: + field_off = map->record->task_work_off; + break; + default: + verifier_bug(env, "unsupported BTF field type: %s\n", struct_name); return -EINVAL; } + if (field_off != val + reg->off) { + verbose(env, "off %lld doesn't point to 'struct %s' that is at %d\n", + val + reg->off, struct_name, field_off); + return -EINVAL; + } + return 0; +} + +static int process_timer_func(struct bpf_verifier_env *env, int regno, + struct bpf_call_arg_meta *meta) +{ + struct bpf_reg_state *regs = cur_regs(env), *reg = ®s[regno]; + struct bpf_map *map = reg->map_ptr; + int err; + + err = check_map_field_pointer(env, regno, BPF_TIMER); + if (err) + return err; + if (meta->map_ptr) { verifier_bug(env, "Two map pointers in a timer helper"); return -EFAULT; @@ -8489,6 +8517,26 @@ static int process_wq_func(struct bpf_verifier_env *env, int regno, return 0; } +static int process_task_work_func(struct bpf_verifier_env *env, int regno, + struct bpf_kfunc_call_arg_meta *meta) +{ + struct bpf_reg_state *regs = cur_regs(env), *reg = ®s[regno]; + struct bpf_map *map = reg->map_ptr; + int err; + + err = check_map_field_pointer(env, regno, BPF_TASK_WORK); + if (err) + return err; + + if (meta->map.ptr) { + verifier_bug(env, "Two map pointers in a bpf_task_work helper"); + return -EFAULT; + } + meta->map.uid = reg->map_uid; + meta->map.ptr = map; + return 0; +} + static int process_kptr_func(struct bpf_verifier_env *env, int regno, struct bpf_call_arg_meta *meta) { @@ -10318,6 +10366,8 @@ typedef int (*set_callee_state_fn)(struct bpf_verifier_env *env, struct bpf_func_state *callee, int insn_idx); +static bool is_task_work_add_kfunc(u32 func_id); + static int set_callee_state(struct bpf_verifier_env *env, struct bpf_func_state *caller, struct bpf_func_state *callee, int insn_idx); @@ -10536,7 +10586,8 @@ static int push_callback_call(struct bpf_verifier_env *env, struct bpf_insn *ins env->subprog_info[subprog].is_async_cb = true; async_cb = push_async_cb(env, env->subprog_info[subprog].start, insn_idx, subprog, - is_bpf_wq_set_callback_impl_kfunc(insn->imm)); + is_bpf_wq_set_callback_impl_kfunc(insn->imm) || + is_task_work_add_kfunc(insn->imm)); if (!async_cb) return -EFAULT; callee = async_cb->frame[0]; @@ -10764,7 +10815,7 @@ static int set_timer_callback_state(struct bpf_verifier_env *env, __mark_reg_not_init(env, &callee->regs[BPF_REG_4]); __mark_reg_not_init(env, &callee->regs[BPF_REG_5]); callee->in_async_callback_fn = true; - callee->callback_ret_range = retval_range(0, 1); + callee->callback_ret_range = retval_range(0, 0); return 0; } @@ -10851,6 +10902,36 @@ static int set_rbtree_add_callback_state(struct bpf_verifier_env *env, return 0; } +static int set_task_work_schedule_callback_state(struct bpf_verifier_env *env, + struct bpf_func_state *caller, + struct bpf_func_state *callee, + int insn_idx) +{ + struct bpf_map *map_ptr = caller->regs[BPF_REG_3].map_ptr; + + /* + * callback_fn(struct bpf_map *map, void *key, void *value); + */ + callee->regs[BPF_REG_1].type = CONST_PTR_TO_MAP; + __mark_reg_known_zero(&callee->regs[BPF_REG_1]); + callee->regs[BPF_REG_1].map_ptr = map_ptr; + + callee->regs[BPF_REG_2].type = PTR_TO_MAP_KEY; + __mark_reg_known_zero(&callee->regs[BPF_REG_2]); + callee->regs[BPF_REG_2].map_ptr = map_ptr; + + callee->regs[BPF_REG_3].type = PTR_TO_MAP_VALUE; + __mark_reg_known_zero(&callee->regs[BPF_REG_3]); + callee->regs[BPF_REG_3].map_ptr = map_ptr; + + /* unused */ + __mark_reg_not_init(env, &callee->regs[BPF_REG_4]); + __mark_reg_not_init(env, &callee->regs[BPF_REG_5]); + callee->in_async_callback_fn = true; + callee->callback_ret_range = retval_range(S32_MIN, S32_MAX); + return 0; +} + static bool is_rbtree_lock_required_kfunc(u32 btf_id); /* Are we currently verifying the callback for a rbtree helper that must @@ -11975,6 +12056,7 @@ enum { KF_ARG_RB_NODE_ID, KF_ARG_WORKQUEUE_ID, KF_ARG_RES_SPIN_LOCK_ID, + KF_ARG_TASK_WORK_ID, }; BTF_ID_LIST(kf_arg_btf_ids) @@ -11985,6 +12067,7 @@ BTF_ID(struct, bpf_rb_root) BTF_ID(struct, bpf_rb_node) BTF_ID(struct, bpf_wq) BTF_ID(struct, bpf_res_spin_lock) +BTF_ID(struct, bpf_task_work) static bool __is_kfunc_ptr_arg_type(const struct btf *btf, const struct btf_param *arg, int type) @@ -12033,6 +12116,11 @@ static bool is_kfunc_arg_wq(const struct btf *btf, const struct btf_param *arg) return __is_kfunc_ptr_arg_type(btf, arg, KF_ARG_WORKQUEUE_ID); } +static bool is_kfunc_arg_task_work(const struct btf *btf, const struct btf_param *arg) +{ + return __is_kfunc_ptr_arg_type(btf, arg, KF_ARG_TASK_WORK_ID); +} + static bool is_kfunc_arg_res_spin_lock(const struct btf *btf, const struct btf_param *arg) { return __is_kfunc_ptr_arg_type(btf, arg, KF_ARG_RES_SPIN_LOCK_ID); @@ -12120,6 +12208,7 @@ enum kfunc_ptr_arg_type { KF_ARG_PTR_TO_WORKQUEUE, KF_ARG_PTR_TO_IRQ_FLAG, KF_ARG_PTR_TO_RES_SPIN_LOCK, + KF_ARG_PTR_TO_TASK_WORK, }; enum special_kfunc_type { @@ -12169,6 +12258,8 @@ enum special_kfunc_type { KF_bpf_res_spin_lock_irqsave, KF_bpf_res_spin_unlock_irqrestore, KF___bpf_trap, + KF_bpf_task_work_schedule_signal, + KF_bpf_task_work_schedule_resume, }; BTF_ID_LIST(special_kfunc_list) @@ -12237,6 +12328,14 @@ BTF_ID(func, bpf_res_spin_unlock) BTF_ID(func, bpf_res_spin_lock_irqsave) BTF_ID(func, bpf_res_spin_unlock_irqrestore) BTF_ID(func, __bpf_trap) +BTF_ID(func, bpf_task_work_schedule_signal) +BTF_ID(func, bpf_task_work_schedule_resume) + +static bool is_task_work_add_kfunc(u32 func_id) +{ + return func_id == special_kfunc_list[KF_bpf_task_work_schedule_signal] || + func_id == special_kfunc_list[KF_bpf_task_work_schedule_resume]; +} static bool is_kfunc_ret_null(struct bpf_kfunc_call_arg_meta *meta) { @@ -12327,6 +12426,9 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env, if (is_kfunc_arg_wq(meta->btf, &args[argno])) return KF_ARG_PTR_TO_WORKQUEUE; + if (is_kfunc_arg_task_work(meta->btf, &args[argno])) + return KF_ARG_PTR_TO_TASK_WORK; + if (is_kfunc_arg_irq_flag(meta->btf, &args[argno])) return KF_ARG_PTR_TO_IRQ_FLAG; @@ -12670,7 +12772,8 @@ static bool is_sync_callback_calling_kfunc(u32 btf_id) static bool is_async_callback_calling_kfunc(u32 btf_id) { - return btf_id == special_kfunc_list[KF_bpf_wq_set_callback_impl]; + return btf_id == special_kfunc_list[KF_bpf_wq_set_callback_impl] || + is_task_work_add_kfunc(btf_id); } static bool is_bpf_throw_kfunc(struct bpf_insn *insn) @@ -13051,7 +13154,8 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ verbose(env, "pointer in R%d isn't map pointer\n", regno); return -EINVAL; } - if (meta->map.ptr && reg->map_ptr->record->wq_off >= 0) { + if (meta->map.ptr && (reg->map_ptr->record->wq_off >= 0 || + reg->map_ptr->record->task_work_off >= 0)) { /* Use map_uid (which is unique id of inner map) to reject: * inner_map1 = bpf_map_lookup_elem(outer_map, key1) * inner_map2 = bpf_map_lookup_elem(outer_map, key2) @@ -13066,6 +13170,12 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ */ if (meta->map.ptr != reg->map_ptr || meta->map.uid != reg->map_uid) { + if (reg->map_ptr->record->task_work_off >= 0) { + verbose(env, + "bpf_task_work pointer in R2 map_uid=%d doesn't match map pointer in R3 map_uid=%d\n", + meta->map.uid, reg->map_uid); + return -EINVAL; + } verbose(env, "workqueue pointer in R1 map_uid=%d doesn't match map pointer in R2 map_uid=%d\n", meta->map.uid, reg->map_uid); @@ -13104,6 +13214,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ case KF_ARG_PTR_TO_REFCOUNTED_KPTR: case KF_ARG_PTR_TO_CONST_STR: case KF_ARG_PTR_TO_WORKQUEUE: + case KF_ARG_PTR_TO_TASK_WORK: case KF_ARG_PTR_TO_IRQ_FLAG: case KF_ARG_PTR_TO_RES_SPIN_LOCK: break; @@ -13397,6 +13508,15 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_ if (ret < 0) return ret; break; + case KF_ARG_PTR_TO_TASK_WORK: + if (reg->type != PTR_TO_MAP_VALUE) { + verbose(env, "arg#%d doesn't point to a map value\n", i); + return -EINVAL; + } + ret = process_task_work_func(env, regno, meta); + if (ret < 0) + return ret; + break; case KF_ARG_PTR_TO_IRQ_FLAG: if (reg->type != PTR_TO_STACK) { verbose(env, "arg#%d doesn't point to an irq flag on stack\n", i); @@ -13763,6 +13883,16 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, } } + if (is_task_work_add_kfunc(meta.func_id)) { + err = push_callback_call(env, insn, insn_idx, meta.subprogno, + set_task_work_schedule_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); @@ -17048,9 +17178,8 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char } if (frame->in_async_callback_fn) { - /* enforce return zero from async callbacks like timer */ exit_ctx = "At async callback return"; - range = retval_range(0, 0); + range = frame->callback_ret_range; goto enforce_retval; } |
