In the Linux kernel, the following vulnerability has been resolved: crypto: pcrypt - Fix hungtask for PADATA_RESET We found a hungtask bug in test_aead_vec_cfg as follows: INFO: task cryptomgr_test:391009 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. Call trace: __switch_to+0x98/0xe0 __schedule+0x6c4/0xf40 schedule+0xd8/0x1b4 schedule_timeout+0x474/0x560 wait_for_common+0x368/0x4e0 wait_for_completion+0x20/0x30 wait_for_completion+0x20/0x30 test_aead_vec_cfg+0xab4/0xd50 test_aead+0x144/0x1f0 alg_test_aead+0xd8/0x1e0 alg_test+0x634/0x890 cryptomgr_test+0x40/0x70 kthread+0x1e0/0x220 ret_from_fork+0x10/0x18 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, we replace the return err -EBUSY with -EAGAIN, which means parallel_data is changing, and the caller should call it again. v3: remove retry and just change the return err. v2: introduce padata_try_do_parallel() in pcrypt_aead_encrypt and pcrypt_aead_decrypt to solve the hungtask.
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