Commit 32fff239 authored Feb 22, 2018 by Eric Dumazet Committed by Daniel Borkmann Feb 22, 2018

bpf: add schedule points in percpu arrays management



syszbot managed to trigger RCU detected stalls in
bpf_array_free_percpu()

It takes time to allocate a huge percpu map, but even more time to free
it.

Since we run in process context, use cond_resched() to yield cpu if
needed.

Fixes: a10423b8 ("bpf: introduce BPF_MAP_TYPE_PERCPU_ARRAY map")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

parent 80475c48

kernel/bpf/arraymap.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -26,8 +26,10 @@ static void bpf_array_free_percpu(struct bpf_array *array)
		{
		int i;

		for (i = 0; i < array->map.max_entries; i++)
		for (i = 0; i < array->map.max_entries; i++) {
		free_percpu(array->pptrs[i]);
		cond_resched();
		}
		}

		static int bpf_array_alloc_percpu(struct bpf_array *array)
		@@ -43,6 +45,7 @@ static int bpf_array_alloc_percpu(struct bpf_array *array)
		return -ENOMEM;
		}
		array->pptrs[i] = ptr;
		cond_resched();
		}

		return 0;