FreeBSD: disable the use of hardware crypto offload drivers for now

First, the crypto request completion handler contains a bug in that it
fails to reset fs_done correctly after the request is completed.  This
is only a problem for asynchronous drivers.  Second, some hardware
drivers have input constraints which ZFS does not satisfy.  For
instance, ccp(4) apparently requires the AAD length for AES-GCM to be a
multiple of the cipher block size, and with qat(4) the AES-GCM AAD
length may not be longer than 240 bytes.  FreeBSD's generic crypto
framework doesn't have a mechanism to automatically fall back to a
software implementation if a hardware driver cannot process a request,
and ZFS does not tolerate such errors.

The plan is to implement such a fallback mechanism, but with FreeBSD
13.0 approaching we should simply disable the use hardware drivers for
now.

Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Mark Johnston <markj@FreeBSD.org>
Closes #11612

diff --git a/module/os/freebsd/zfs/crypto_os.c b/module/os/freebsd/zfs/crypto_os.c
index fbf998416234e90e6c6e8071e9aeb0429b1ff23d..03d14ed7cf5c2ddaa82e5b08ee4221a5fbc748cf 100644 (file)
--- a/module/os/freebsd/zfs/crypto_os.c
+++ b/module/os/freebsd/zfs/crypto_os.c
@@ -293,8 +293,19 @@ freebsd_crypt_newsession(freebsd_crypt_session_t *sessp,
                error = ENOTSUP;
                goto bad;
        }
-       error = crypto_newsession(&sessp->fs_sid, &csp,
-           CRYPTOCAP_F_HARDWARE | CRYPTOCAP_F_SOFTWARE);
+
+       /*
+        * Disable the use of hardware drivers on FreeBSD 13 and later since
+        * common crypto offload drivers impose constraints on AES-GCM AAD
+        * lengths that make them unusable for ZFS, and we currently do not have
+        * a mechanism to fall back to a software driver for requests not
+        * handled by a hardware driver.
+        *
+        * On 12 we continue to permit the use of hardware drivers since
+        * CPU-accelerated drivers such as aesni(4) register themselves as
+        * hardware drivers.
+        */
+       error = crypto_newsession(&sessp->fs_sid, &csp, CRYPTOCAP_F_SOFTWARE);
        mtx_init(&sessp->fs_lock, "FreeBSD Cryptographic Session Lock",
            NULL, MTX_DEF);
        crypt_sessions++;