From: Eric Dumazet <edumazet@xxxxxxxxxx> commit 75134f16e7dd0007aa474b281935c5f42e79f2c8 upstream. syzbot reported various soft lockups caused by bpf batch operations. INFO: task kworker/1:1:27 blocked for more than 140 seconds. INFO: task hung in rcu_barrier Nothing prevents batch ops to process huge amount of data, we need to add schedule points in them. Note that maybe_wait_bpf_programs(map) calls from generic_map_delete_batch() can be factorized by moving the call after the loop. This will be done later in -next tree once we get this fix merged, unless there is strong opinion doing this optimization sooner. Fixes: aa2e93b8e58e ("bpf: Add generic support for update and delete batch ops") Fixes: cb4d03ab499d ("bpf: Add generic support for lookup batch op") Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx> Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx> Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx> Reviewed-by: Stanislav Fomichev <sdf@xxxxxxxxxx> Acked-by: Brian Vazquez <brianvv@xxxxxxxxxx> Link: https://lore.kernel.org/bpf/20220217181902.808742-1-eric.dumazet@xxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/bpf/syscall.c | 3 +++ 1 file changed, 3 insertions(+) --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1308,6 +1308,7 @@ int generic_map_delete_batch(struct bpf_ maybe_wait_bpf_programs(map); if (err) break; + cond_resched(); } if (copy_to_user(&uattr->batch.count, &cp, sizeof(cp))) err = -EFAULT; @@ -1365,6 +1366,7 @@ int generic_map_update_batch(struct bpf_ if (err) break; + cond_resched(); } if (copy_to_user(&uattr->batch.count, &cp, sizeof(cp))) @@ -1462,6 +1464,7 @@ int generic_map_lookup_batch(struct bpf_ swap(prev_key, key); retry = MAP_LOOKUP_RETRIES; cp++; + cond_resched(); } if (err == -EFAULT) Patches currently in stable-queue which might be from edumazet@xxxxxxxxxx are queue-5.10/net-__pskb_pull_tail-pskb_carve_frag_list-drop_monitor-friends.patch queue-5.10/bpf-add-schedule-points-in-batch-ops.patch queue-5.10/io_uring-add-a-schedule-point-in-io_add_buffers.patch