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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: a10423b87a ("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>
This commit is contained in:
Eric Dumazet 2018-02-22 08:33:24 -08:00 committed by Daniel Borkmann
parent 80475c48c6
commit 32fff239de
1 changed files with 4 additions and 1 deletions
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5
kernel/bpf/arraymap.c
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@ -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;