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 (cherry picked from commit e9c856cabefb71d47b2eeb197f72c9c88e9b45b0) --- 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 7ac6c52b25eb..45de8a4923e2 100644 --- 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); }