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author | Eric Biggers <ebiggers@google.com> | 2020-06-04 11:52:53 -0700 |
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committer | Herbert Xu <herbert@gondor.apana.org.au> | 2020-06-15 17:38:54 +1000 |
commit | 2dae7d67d06328e0273dd45a995c6396f89f4e4a (patch) | |
tree | 37f734e4d4d783490aee43a5aea129e7abc2f441 /crypto/async_tx | |
parent | 4c636c1916324c5e8d13479b52f21f5152af2742 (diff) | |
download | linux-crypto-2dae7d67d06328e0273dd45a995c6396f89f4e4a.tar.gz linux-crypto-2dae7d67d06328e0273dd45a995c6396f89f4e4a.zip |
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 <gerow@google.com>
Fixes: 582802f3e378 ("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 Lüke <kai@kinvolk.io>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'crypto/async_tx')
0 files changed, 0 insertions, 0 deletions