[PATCH] [v2] drbd: dynamically allocate shash descriptor

From: Arnd Bergmann <arnd@arndb.de>
To: Philipp Reisner <philipp.reisner@linbit.com>,
	Lars Ellenberg <lars.ellenberg@linbit.com>,
	Jens Axboe <axboe@kernel.dk>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Roland Kammerer <roland.kammerer@linbit.com>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Eric Biggers <ebiggers@google.com>,
	Kees Cook <keescook@chromium.org>,
	drbd-dev@lists.linbit.com, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com
Subject: [PATCH] [v2] drbd: dynamically allocate shash descriptor
Date: Mon, 22 Jul 2019 14:26:34 +0200	[thread overview]
Message-ID: <20190722122647.351002-1-arnd@arndb.de> (raw)

Building with clang and KASAN, we get a warning about an overly large
stack frame on 32-bit architectures:

drivers/block/drbd/drbd_receiver.c:921:31: error: stack frame size of 1280 bytes in function 'conn_connect'
      [-Werror,-Wframe-larger-than=]

We already allocate other data dynamically in this function, so
just do the same for the shash descriptor, which makes up most of
this memory.

Link: https://lore.kernel.org/lkml/20190617132440.2721536-1-arnd@arndb.de/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
v2:
- don't try to zero a NULL descriptor pointer,
  based on review from Roland Kammerer.
---
 drivers/block/drbd/drbd_receiver.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 90ebfcae0ce6..2b3103c30857 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -5417,7 +5417,7 @@ static int drbd_do_auth(struct drbd_connection *connection)
 	unsigned int key_len;
 	char secret[SHARED_SECRET_MAX]; /* 64 byte */
 	unsigned int resp_size;
-	SHASH_DESC_ON_STACK(desc, connection->cram_hmac_tfm);
+	struct shash_desc *desc;
 	struct packet_info pi;
 	struct net_conf *nc;
 	int err, rv;
@@ -5430,6 +5430,13 @@ static int drbd_do_auth(struct drbd_connection *connection)
 	memcpy(secret, nc->shared_secret, key_len);
 	rcu_read_unlock();
 
+	desc = kmalloc(sizeof(struct shash_desc) +
+		       crypto_shash_descsize(connection->cram_hmac_tfm),
+		       GFP_KERNEL);
+	if (!desc) {
+		rv = -1;
+		goto fail;
+	}
 	desc->tfm = connection->cram_hmac_tfm;
 
 	rv = crypto_shash_setkey(connection->cram_hmac_tfm, (u8 *)secret, key_len);
@@ -5571,7 +5578,10 @@ static int drbd_do_auth(struct drbd_connection *connection)
 	kfree(peers_ch);
 	kfree(response);
 	kfree(right_response);
-	shash_desc_zero(desc);
+	if (desc) {
+		shash_desc_zero(desc);
+		kfree(desc);
+	}
 
 	return rv;
 }
-- 
2.20.0

