crypto:padata: Fix return err for PADATA_RESET

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7RZMT


CVE: NA

--------------------------------

We found a hungtask bug in test_aead_vec_cfg as follows:

[ 2297.136299] INFO: task cryptomgr_test:391009 blocked for more than 120 seconds.
[ 2297.157611] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 2297.168592] task:cryptomgr_test  state:D stack:    0 pid:391009 ppid:     2 flags:0x00000208
[ 2297.168611] Call trace:
[ 2297.193085]  __switch_to+0x98/0xe0
[ 2297.199815]  __schedule+0x6c4/0xf40
[ 2297.206674]  schedule+0xd8/0x1b4
[ 2297.213223]  schedule_timeout+0x474/0x560
[ 2297.220594]  wait_for_common+0x368/0x4e0
[ 2297.227929]  wait_for_completion+0x20/0x30
[ 2297.235480]  test_aead_vec_cfg+0xab4/0xd50
[ 2297.243045]  test_aead+0x144/0x1f0
[ 2297.249986]  alg_test_aead+0xd8/0x1e0
[ 2297.257148]  alg_test+0x634/0x890
[ 2297.264013]  cryptomgr_test+0x40/0x70
[ 2297.271243]  kthread+0x1e0/0x220
[ 2297.278070]  ret_from_fork+0x10/0x18
[ 2297.285503] Kernel panic - not syncing: hung_task: blocked tasks

For padata_do_parallel, when the return err is 0 or -EBUSY, it will call
wait_for_completion(&wait->completion) in test_aead_vec_cfg. In normal
case, aead_request_complete() will be called in pcrypt_aead_serial and the
return err is 0 for padata_do_parallel. But, when pinst->flags is
PADATA_RESET, the return err is -EBUSY for padata_do_parallel, and it
won't call aead_request_complete(). Therefore, test_aead_vec_cfg will
hung at wait_for_completion(&wait->completion), which will cause
hungtask.

The problem comes as following:
(padata_do_parallel)                 |
    rcu_read_lock_bh();              |
    err = -EINVAL;                   |   (padata_replace)
                                     |     pinst->flags |= PADATA_RESET;
    err = -EBUSY                     |
    if (pinst->flags & PADATA_RESET) |
        rcu_read_unlock_bh()         |
        return err                   |

In order to resolve the problem, change the return err to -EAGAIN when
pinst->flags is set PADATA_RESET.

Signed-off-by: Lu Jialin <lujialin4@huawei.com>