From: Eric Dumazet edumazet@google.com
[ upstream commit 32fff239de37ef226d5b66329dd133f64d63b22d ]
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: a10423b87a7e ("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 --- kernel/bpf/arraymap.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c index e76aa67..8596aa3 100644 --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -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;