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

commit e9c856cabefb71d47b2eeb197f72c9c88e9b45b0 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 7ac6c52b25ebc8dcb93df83844f5e796740b8206..45de8a4923e21dc390a1012250a3ec7fed8e0a94 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -3142,6 +3142,9 @@ 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)
@@ -3149,9 +3152,6 @@ 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);
 }