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authorEric Biggers <ebiggers@google.com>2020-06-04 11:52:53 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-06-25 15:33:09 +0200
commitc0ef44cbed8af7bafd29225be441e94d488405c5 (patch)
treefbed6731fc5df11de3db404e293a37b81e65d537
parentb3ad0cdbdca3c8593bc8bb8f51bb0177597cbf6c (diff)
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crypto: algboss - don't wait during notifier callback
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@google.com> Fixes: 398710379f51 ("crypto: algapi - Move larval completion into algboss") Cc: <stable@vger.kernel.org> # v3.6+ Cc: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Eric Biggers <ebiggers@google.com> Reported-by: Kai L√ľke <kai@kinvolk.io> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--crypto/algboss.c2
1 files changed, 0 insertions, 2 deletions
diff --git a/crypto/algboss.c b/crypto/algboss.c
index 5e6df2a087fa..445da4a0618f 100644
--- a/crypto/algboss.c
+++ b/crypto/algboss.c
@@ -193,8 +193,6 @@ 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: