From 7bb62d0cd8ac709dc07cc0b7e84889d4ec09dd66 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Thu, 4 Jun 2020 11:52:53 -0700 Subject: [PATCH] crypto: algboss - don't wait during notifier callback MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Fixes: 398710379f51 ("crypto: algapi - Move larval completion into algboss") Cc: # v3.6+ Cc: Martin K. Petersen Signed-off-by: Eric Biggers Reported-by: Kai Lüke Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman --- crypto/algboss.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/crypto/algboss.c b/crypto/algboss.c index a62149d6c839..2d41e67532c0 100644 --- a/crypto/algboss.c +++ b/crypto/algboss.c @@ -188,8 +188,6 @@ static int cryptomgr_schedule_probe(struct crypto_larval *larval) if (IS_ERR(thread)) goto err_put_larval; - wait_for_completion_interruptible(&larval->completion); - return NOTIFY_STOP; err_put_larval: