diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/hashtab.c | 24 |
1 files changed, 20 insertions, 4 deletions
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index a1468e3f5af2..65711a220fe0 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -27,6 +27,26 @@ .map_delete_batch = \ generic_map_delete_batch +/* + * The bucket lock has two protection scopes: + * + * 1) Serializing concurrent operations from BPF programs on differrent + * CPUs + * + * 2) Serializing concurrent operations from BPF programs and sys_bpf() + * + * BPF programs can execute in any context including perf, kprobes and + * tracing. As there are almost no limits where perf, kprobes and tracing + * can be invoked from the lock operations need to be protected against + * deadlocks. Deadlocks can be caused by recursion and by an invocation in + * the lock held section when functions which acquire this lock are invoked + * from sys_bpf(). BPF recursion is prevented by incrementing the per CPU + * variable bpf_prog_active, which prevents BPF programs attached to perf + * events, kprobes and tracing to be invoked before the prior invocation + * from one of these contexts completed. sys_bpf() uses the same mechanism + * by pinning the task to the current CPU and incrementing the recursion + * protection accross the map operation. + */ struct bucket { struct hlist_nulls_head head; raw_spinlock_t lock; @@ -884,7 +904,6 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value, */ } - /* bpf_map_update_elem() can be called in_irq() */ raw_spin_lock_irqsave(&b->lock, flags); l_old = lookup_elem_raw(head, hash, key, key_size); @@ -964,7 +983,6 @@ static int htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value, return -ENOMEM; memcpy(l_new->key + round_up(map->key_size, 8), value, map->value_size); - /* bpf_map_update_elem() can be called in_irq() */ raw_spin_lock_irqsave(&b->lock, flags); l_old = lookup_elem_raw(head, hash, key, key_size); @@ -1019,7 +1037,6 @@ static int __htab_percpu_map_update_elem(struct bpf_map *map, void *key, b = __select_bucket(htab, hash); head = &b->head; - /* bpf_map_update_elem() can be called in_irq() */ raw_spin_lock_irqsave(&b->lock, flags); l_old = lookup_elem_raw(head, hash, key, key_size); @@ -1083,7 +1100,6 @@ static int __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key, return -ENOMEM; } - /* bpf_map_update_elem() can be called in_irq() */ raw_spin_lock_irqsave(&b->lock, flags); l_old = lookup_elem_raw(head, hash, key, key_size); |