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Date: Tue, 23 Jun 2020 21:58:21 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Mike Gerow <gerow@...gle.com>, "Martin K. Petersen" <martin.petersen@...cle.com>, Eric Biggers <ebiggers@...gle.com>, Kai Lüke <kai@...volk.io>, Herbert Xu <herbert@...dor.apana.org.au> Subject: [PATCH 5.4 306/314] crypto: algboss - dont wait during notifier callback From: Eric Biggers <ebiggers@...gle.com> commit 77251e41f89a813b4090f5199442f217bbf11297 upstream. When a crypto template needs to be instantiated, CRYPTO_MSG_ALG_REQUEST is sent to crypto_chain. cryptomgr_schedule_probe() handles this by starting a thread to instantiate the template, then waiting for this thread to complete via crypto_larval::completion. This can deadlock because instantiating the template may require loading modules, and this (apparently depending on userspace) may need to wait for the crc-t10dif module (lib/crc-t10dif.c) to be loaded. But crc-t10dif's module_init function uses crypto_register_notifier() and therefore takes crypto_chain.rwsem for write. That can't proceed until the notifier callback has finished, as it holds this semaphore for read. Fix this by removing the wait on crypto_larval::completion from within cryptomgr_schedule_probe(). It's actually unnecessary because crypto_alg_mod_lookup() calls crypto_larval_wait() itself after sending CRYPTO_MSG_ALG_REQUEST. This only actually became a problem in v4.20 due to commit b76377543b73 ("crc-t10dif: Pick better transform if one becomes available"), but the unnecessary wait was much older. BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=207159 Reported-by: Mike Gerow <gerow@...gle.com> Fixes: 398710379f51 ("crypto: algapi - Move larval completion into algboss") Cc: <stable@...r.kernel.org> # v3.6+ Cc: Martin K. Petersen <martin.petersen@...cle.com> Signed-off-by: Eric Biggers <ebiggers@...gle.com> Reported-by: Kai Lüke <kai@...volk.io> Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- crypto/algboss.c | 2 -- 1 file changed, 2 deletions(-) --- a/crypto/algboss.c +++ b/crypto/algboss.c @@ -188,8 +188,6 @@ static int cryptomgr_schedule_probe(stru if (IS_ERR(thread)) goto err_put_larval; - wait_for_completion_interruptible(&larval->completion); - return NOTIFY_STOP; err_put_larval:
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