Hi Michal, On Wed, Jul 03, 2019 at 10:21:08PM +0200, Michal Suchánek wrote: > On Wed, 3 Jul 2019 22:30:57 +0800 > Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> wrote: > > > On Tue, Jul 02, 2019 at 02:17:00PM -0700, Eric Biggers wrote: > > > From: Eric Biggers <ebiggers@xxxxxxxxxx> > > > > > > Michal Suchanek reported [1] that running the pcrypt_aead01 test from > > > LTP [2] in a loop and holding Ctrl-C causes a NULL dereference of > > > alg->cra_users.next in crypto_remove_spawns(), via crypto_del_alg(). > > > The test repeatedly uses CRYPTO_MSG_NEWALG and CRYPTO_MSG_DELALG. > > > > > > The crash occurs when the instance that CRYPTO_MSG_DELALG is trying to > > > unregister isn't a real registered algorithm, but rather is a "test > > > larval", which is a special "algorithm" added to the algorithms list > > > while the real algorithm is still being tested. Larvals don't have > > > initialized cra_users, so that causes the crash. Normally pcrypt_aead01 > > > doesn't trigger this because CRYPTO_MSG_NEWALG waits for the algorithm > > > to be tested; however, CRYPTO_MSG_NEWALG returns early when interrupted. > > > > > Do you have some way to reproduce this reliably? > > I suppose you would have to send a signal to the process for the call > to get interrupted, right? > It reproduced pretty reliably for me with what you suggested. Just typing in terminal: while true; do pcrypt_aead01; done and then holding Ctrl-C. If I have time I'll try writing an LTP test that specifically reproduces it. Yes, it would involve sending a signal to a thread or process that's executing CRYPTO_MSG_NEWALG (unless I find a better way). - Eric
