From: Eric Biggers Date: Thu, 4 Jun 2020 18:52:53 +0000 (-0700) Subject: crypto: algboss - don't wait during notifier callback X-Git-Tag: v5.8-rc2~5^2~2 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=77251e41f89a813b4090f5199442f217bbf11297;p=linux-block.git crypto: algboss - don't wait during notifier callback 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 --- diff --git a/crypto/algboss.c b/crypto/algboss.c index 535f1f87e6c1..5ebccbd6b74e 100644 --- a/crypto/algboss.c +++ b/crypto/algboss.c @@ -178,8 +178,6 @@ 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: