Commit 31f23a6a authored Sep 17, 2020 by Muchun Song Committed by Daniel Borkmann Sep 21, 2020

bpf: Fix potential call bpf_link_free() in atomic context



The in_atomic() macro cannot always detect atomic context, in particular,
it cannot know about held spinlocks in non-preemptible kernels. Although,
there is no user call bpf_link_put() with holding spinlock now, be on the
safe side, so we can avoid this in the future.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200917074453.20621-1-songmuchun@bytedance.com

parent 70b97111

kernel/bpf/syscall.c

+2 −6

Original line number	Diff line number	Diff line
		@@ -2345,12 +2345,8 @@ void bpf_link_put(struct bpf_link *link)
		if (!atomic64_dec_and_test(&link->refcnt))
		return;

		if (in_atomic()) {
		INIT_WORK(&link->work, bpf_link_put_deferred);
		schedule_work(&link->work);
		} else {
		bpf_link_free(link);
		}
		}

		static int bpf_link_release(struct inode inode, struct file filp)

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