bpf: put uprobe link's path and task in release callback

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>
Link: https://lore.kernel.org/r/20240328052426.3042617-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 0a5c4efc73c3674fa225757c6f4ccc921f758b57..0b73fe5f7206bf779cf2743c116b49fdec7e7fdc 100644 (file)
--- 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);
 }