From: Andrii Nakryiko <andrii@kernel.org>
To: bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net,
martin.lau@kernel.org
Cc: jolsa@kernel.org, Andrii Nakryiko <andrii@kernel.org>
Subject: [PATCH bpf 1/2] bpf: put uprobe link's path and task in release callback
Date: Wed, 27 Mar 2024 22:24:25 -0700 [thread overview]
Message-ID: <20240328052426.3042617-1-andrii@kernel.org> (raw)
There is no need to delay putting either path or task to deallocation
step. It can be done right after bpf_uprobe_unregister. Between release
and dealloc, there could be still some running BPF programs, but they
don't access either task or path, only data in link->uprobes, so it is
safe to do.
On the other hand, doing path_put() in dealloc callback makes this
dealloc sleepable because path_put() itself might sleep. Which is
problematic due to the need to call uprobe's dealloc through call_rcu(),
which is what is done in the next bug fix patch. So solve the problem by
releasing these resources early.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
kernel/trace/bpf_trace.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 0a5c4efc73c3..0b73fe5f7206 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -3157,6 +3157,9 @@ static void bpf_uprobe_multi_link_release(struct bpf_link *link)
umulti_link = container_of(link, struct bpf_uprobe_multi_link, link);
bpf_uprobe_unregister(&umulti_link->path, umulti_link->uprobes, umulti_link->cnt);
+ if (umulti_link->task)
+ put_task_struct(umulti_link->task);
+ path_put(&umulti_link->path);
}
static void bpf_uprobe_multi_link_dealloc(struct bpf_link *link)
@@ -3164,9 +3167,6 @@ static void bpf_uprobe_multi_link_dealloc(struct bpf_link *link)
struct bpf_uprobe_multi_link *umulti_link;
umulti_link = container_of(link, struct bpf_uprobe_multi_link, link);
- if (umulti_link->task)
- put_task_struct(umulti_link->task);
- path_put(&umulti_link->path);
kvfree(umulti_link->uprobes);
kfree(umulti_link);
}
--
2.43.0
next reply other threads:[~2024-03-28 5:24 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-28 5:24 Andrii Nakryiko [this message]
2024-03-28 5:24 ` [PATCH bpf 2/2] bpf: support deferring bpf_link dealloc to after RCU grace period Andrii Nakryiko
2024-03-28 10:10 ` Jiri Olsa
2024-03-29 2:00 ` [PATCH bpf 1/2] bpf: put uprobe link's path and task in release callback patchwork-bot+netdevbpf
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