ut 21. 8. 2018 o 16:18 Stephan Mueller <smueller@xxxxxxxxxx> napísal(a): > Am Dienstag, 21. August 2018, 14:48:11 CEST schrieb Ondrej Mosnáček: > > Hi Ondrej, Marcelo, > > (+Marcelo) > > > Looking at crypto/algif_skcipher.c, I can see that skcipher_recvmsg() > > holds the socket lock the whole time and yet passes > > CRYPTO_TFM_REQ_MAY_SLEEP to the cipher implementation. Isn't that > > wrong? > > I think you are referring to lock_sock(sk)? > > If so, this should not be the culprit: the socket lock is in essence a mutex- > like operation with its own wait queue that it allowed to sleep. In > lock_sock_nested that is called by lock_sock it even has the call of > might_sleep which indicates that the caller may be put to sleep. > > Looking into the code (without too much debugging) I see in the function > p8_aes_cbc_encrypt that is part of the stack trace the call to > preempt_disable() which starts an atomic context. The preempt_enable() is > invoked after the walk operation. > > The preempt_disable increases the preempt_count. That counter is used by > in_atomic() to check whether we are in atomic context. > > The issue is that blkcipher_walk_done may call crypto_yield() which then > invokes cond_resched if the implementation is allowed to sleep. Indeed, you're right, the issue is actually in the vmx_crypto code. I remember having looked at the 'ctr(aes)' implementation in there a few days ago (I think I was trying to debug this very issue, but for some reason I only looked at ctr(aes)...) and I didn't find any bug, so that's why I jumped to suspecting the algif_skcipher code... I should have double-checked :) It turns out the 'cbc(aes)' (and actually also 'xts(aes)') implementation is coded a bit differently and they both *do* contain the sleep-in-atomic bug. I will try to fix them according to the correct CTR implementation and send a patch. Thanks, Ondrej > @Marcelo: shouldn't be the sleep flag be cleared when entering the > preempt_disable section? > > Ciao > Stephan > >
