[PATCH 6.8 181/336] powerpc/crypto/chacha-p10: Fix failure on non Power10

Greg Kroah-Hartman
2024-05-14T10:43:31Z

From: Michael Ellerman <mpe@ellerman.id.au>

[ Upstream commit 69630926011c1f7170a465b7b5c228deb66e9372 ]

The chacha-p10-crypto module provides optimised chacha routines for
Power10. It also selects CRYPTO_ARCH_HAVE_LIB_CHACHA which says it
provides chacha_crypt_arch() to generic code.

Notably the module needs to provide chacha_crypt_arch() regardless of
whether it is loaded on Power10 or an older CPU.

The implementation of chacha_crypt_arch() already has a fallback to
chacha_crypt_generic(), however the module as a whole fails to load on
pre-Power10, because of the use of module_cpu_feature_match().

This breaks for example loading wireguard:

jostaberry-1:~ # modprobe -v wireguard
insmod /lib/modules/6.8.0-lp155.8.g7e0e887-default/kernel/arch/powerpc/crypto/chacha-p10-crypto.ko.zst
modprobe: ERROR: could not insert 'wireguard': No such device

Fix it by removing module_cpu_feature_match(), and instead check the
CPU feature manually. If the CPU feature is not found, the module
still loads successfully, but doesn't register the Power10 specific
algorithms. That allows chacha_crypt_generic() to remain available for
use, fixing the problem.

[root@fedora ~]# modprobe -v wireguard
insmod /lib/modules/6.8.0-00001-g786a790c4d79/kernel/net/ipv4/udp_tunnel.ko
insmod /lib/modules/6.8.0-00001-g786a790c4d79/kernel/net/ipv6/ip6_udp_tunnel.ko
insmod /lib/modules/6.8.0-00001-g786a790c4d79/kernel/lib/crypto/libchacha.ko
insmod /lib/modules/6.8.0-00001-g786a790c4d79/kernel/arch/powerpc/crypto/chacha-p10-crypto.ko
insmod /lib/modules/6.8.0-00001-g786a790c4d79/kernel/lib/crypto/libchacha20poly1305.ko
insmod /lib/modules/6.8.0-00001-g786a790c4d79/kernel/drivers/net/wireguard/wireguard.ko
[ 18.910452][ T721] wireguard: allowedips self-tests: pass
[ 18.914999][ T721] wireguard: nonce counter self-tests: pass
[ 19.029066][ T721] wireguard: ratelimiter self-tests: pass
[ 19.029257][ T721] wireguard: WireGuard 1.0.0 loaded. See www.wireguard.com for information.
[ 19.029361][ T721] wireguard: Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.

Reported-by: Michal Suchánek <msuchanek@suse.de>
Closes: https://lore.kernel.org/all/20240315122005.GG20665@kitsune.suse.cz/
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240328130200.3041687-1-mpe@ellerman.id.au
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/powerpc/crypto/chacha-p10-glue.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/crypto/chacha-p10-glue.c b/arch/powerpc/crypto/chacha-p10-glue.c
index 74fb86b0d2097..7c728755852e1 100644
--- a/arch/powerpc/crypto/chacha-p10-glue.c
+++ b/arch/powerpc/crypto/chacha-p10-glue.c
@@ -197,6 +197,9 @@ static struct skcipher_alg algs[] = {

static int __init chacha_p10_init(void)
{
+ if (!cpu_has_feature(CPU_FTR_ARCH_31))
+ return 0;
+
static_branch_enable(&have_p10);

return crypto_register_skciphers(algs, ARRAY_SIZE(algs));
@@ -204,10 +207,13 @@ static int __init chacha_p10_init(void)

static void __exit chacha_p10_exit(void)
{
+ if (!static_branch_likely(&have_p10))
+ return;
+
crypto_unregister_skciphers(algs, ARRAY_SIZE(algs));
}

-module_cpu_feature_match(PPC_MODULE_FEATURE_P10, chacha_p10_init);
+module_init(chacha_p10_init);
module_exit(chacha_p10_exit);

MODULE_DESCRIPTION("ChaCha and XChaCha stream ciphers (P10 accelerated)");
--
2.43.0