diff options
| -rw-r--r-- | include/linux/bpf.h | 20 | ||||
| -rw-r--r-- | kernel/bpf/syscall.c | 39 |
2 files changed, 46 insertions, 13 deletions
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 19d8ca8ac960..e7236facadd4 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1598,6 +1598,11 @@ struct bpf_link { enum bpf_link_type type; const struct bpf_link_ops *ops; struct bpf_prog *prog; + /* whether BPF link itself has "sleepable" semantics, which can differ + * from underlying BPF program having a "sleepable" semantics, as BPF + * link's semantics is determined by target attach hook + */ + bool sleepable; /* rcu is used before freeing, work can be used to schedule that * RCU-based freeing before that, so they never overlap */ @@ -1614,8 +1619,10 @@ struct bpf_link_ops { */ void (*dealloc)(struct bpf_link *link); /* deallocate link resources callback, called after RCU grace period; - * if underlying BPF program is sleepable we go through tasks trace - * RCU GP and then "classic" RCU GP + * if either the underlying BPF program is sleepable or BPF link's + * target hook is sleepable, we'll go through tasks trace RCU GP and + * then "classic" RCU GP; this need for chaining tasks trace and + * classic RCU GPs is designated by setting bpf_link->sleepable flag */ void (*dealloc_deferred)(struct bpf_link *link); int (*detach)(struct bpf_link *link); @@ -2362,6 +2369,9 @@ int bpf_prog_new_fd(struct bpf_prog *prog); void bpf_link_init(struct bpf_link *link, enum bpf_link_type type, const struct bpf_link_ops *ops, struct bpf_prog *prog); +void bpf_link_init_sleepable(struct bpf_link *link, enum bpf_link_type type, + const struct bpf_link_ops *ops, struct bpf_prog *prog, + bool sleepable); int bpf_link_prime(struct bpf_link *link, struct bpf_link_primer *primer); int bpf_link_settle(struct bpf_link_primer *primer); void bpf_link_cleanup(struct bpf_link_primer *primer); @@ -2717,6 +2727,12 @@ static inline void bpf_link_init(struct bpf_link *link, enum bpf_link_type type, { } +static inline void bpf_link_init_sleepable(struct bpf_link *link, enum bpf_link_type type, + const struct bpf_link_ops *ops, struct bpf_prog *prog, + bool sleepable) +{ +} + static inline int bpf_link_prime(struct bpf_link *link, struct bpf_link_primer *primer) { diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index aa7246a399f3..0f5540627911 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -2933,17 +2933,33 @@ static int bpf_obj_get(const union bpf_attr *attr) attr->file_flags); } -void bpf_link_init(struct bpf_link *link, enum bpf_link_type type, - const struct bpf_link_ops *ops, struct bpf_prog *prog) +/* bpf_link_init_sleepable() allows to specify whether BPF link itself has + * "sleepable" semantics, which normally would mean that BPF link's attach + * hook can dereference link or link's underlying program for some time after + * detachment due to RCU Tasks Trace-based lifetime protection scheme. + * BPF program itself can be non-sleepable, yet, because it's transitively + * reachable through BPF link, its freeing has to be delayed until after RCU + * Tasks Trace GP. + */ +void bpf_link_init_sleepable(struct bpf_link *link, enum bpf_link_type type, + const struct bpf_link_ops *ops, struct bpf_prog *prog, + bool sleepable) { WARN_ON(ops->dealloc && ops->dealloc_deferred); atomic64_set(&link->refcnt, 1); link->type = type; + link->sleepable = sleepable; link->id = 0; link->ops = ops; link->prog = prog; } +void bpf_link_init(struct bpf_link *link, enum bpf_link_type type, + const struct bpf_link_ops *ops, struct bpf_prog *prog) +{ + bpf_link_init_sleepable(link, type, ops, prog, false); +} + static void bpf_link_free_id(int id) { if (!id) @@ -3008,20 +3024,21 @@ static void bpf_link_defer_dealloc_mult_rcu_gp(struct rcu_head *rcu) static void bpf_link_free(struct bpf_link *link) { const struct bpf_link_ops *ops = link->ops; - bool sleepable = false; bpf_link_free_id(link->id); - if (link->prog) { - sleepable = link->prog->sleepable; - /* detach BPF program, clean up used resources */ + /* detach BPF program, clean up used resources */ + if (link->prog) ops->release(link); - } if (ops->dealloc_deferred) { - /* schedule BPF link deallocation; if underlying BPF program - * is sleepable, we need to first wait for RCU tasks trace - * sync, then go through "classic" RCU grace period + /* Schedule BPF link deallocation, which will only then + * trigger putting BPF program refcount. + * If underlying BPF program is sleepable or BPF link's target + * attach hookpoint is sleepable or otherwise requires RCU GPs + * to ensure link and its underlying BPF program is not + * reachable anymore, we need to first wait for RCU tasks + * trace sync, and then go through "classic" RCU grace period */ - if (sleepable) + if (link->sleepable || (link->prog && link->prog->sleepable)) call_rcu_tasks_trace(&link->rcu, bpf_link_defer_dealloc_mult_rcu_gp); else call_rcu(&link->rcu, bpf_link_defer_dealloc_rcu_gp); |