diff options
| author | Cong Wang <cong.wang@bytedance.com> | 2024-06-02 21:27:03 +0300 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2024-06-03 19:16:19 +0300 |
| commit | 2884dc7d08d98a89d8d65121524bb7533183a63a (patch) | |
| tree | 2ba0a318481cbdc9dd240af512fc8563635c3354 | |
| parent | 2317dc2c22cc353b699c7d1db47b2fe91f54055c (diff) | |
| download | linux-2884dc7d08d98a89d8d65121524bb7533183a63a.tar.xz | |
bpf: Fix a potential use-after-free in bpf_link_free()
After commit 1a80dbcb2dba, bpf_link can be freed by
link->ops->dealloc_deferred, but the code still tests and uses
link->ops->dealloc afterward, which leads to a use-after-free as
reported by syzbot. Actually, one of them should be sufficient, so
just call one of them instead of both. Also add a WARN_ON() in case
of any problematic implementation.
Fixes: 1a80dbcb2dba ("bpf: support deferring bpf_link dealloc to after RCU grace period")
Reported-by: syzbot+1989ee16d94720836244@syzkaller.appspotmail.com
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20240602182703.207276-1-xiyou.wangcong@gmail.com
| -rw-r--r-- | kernel/bpf/syscall.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 2222c3ff88e7..f45ed6adc092 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -2998,6 +2998,7 @@ static int bpf_obj_get(const union bpf_attr *attr) void bpf_link_init(struct bpf_link *link, enum bpf_link_type type, const struct bpf_link_ops *ops, struct bpf_prog *prog) { + WARN_ON(ops->dealloc && ops->dealloc_deferred); atomic64_set(&link->refcnt, 1); link->type = type; link->id = 0; @@ -3056,16 +3057,17 @@ static void bpf_link_defer_dealloc_mult_rcu_gp(struct rcu_head *rcu) /* bpf_link_free is guaranteed to be called from process context */ 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 */ - link->ops->release(link); + ops->release(link); bpf_prog_put(link->prog); } - if (link->ops->dealloc_deferred) { + 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 @@ -3074,9 +3076,8 @@ static void bpf_link_free(struct bpf_link *link) call_rcu_tasks_trace(&link->rcu, bpf_link_defer_dealloc_mult_rcu_gp); else call_rcu(&link->rcu, bpf_link_defer_dealloc_rcu_gp); - } - if (link->ops->dealloc) - link->ops->dealloc(link); + } else if (ops->dealloc) + ops->dealloc(link); } static void bpf_link_put_deferred(struct work_struct *work) |