linux-kernel - [PATCH] drbd: dynamically allocate shash descriptor

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Date:   Mon, 17 Jun 2019 15:24:13 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Philipp Reisner <philipp.reisner@...bit.com>,
        Lars Ellenberg <lars.ellenberg@...bit.com>,
        Jens Axboe <axboe@...nel.dk>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Roland Kammerer <roland.kammerer@...bit.com>,
        Eric Biggers <ebiggers@...gle.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Kees Cook <keescook@...omium.org>, drbd-dev@...ts.linbit.com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] drbd: dynamically allocate shash descriptor

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.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/block/drbd/drbd_receiver.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 90ebfcae0ce6..10fb26e862d7 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);
@@ -5572,6 +5579,7 @@ static int drbd_do_auth(struct drbd_connection *connection)
 	kfree(response);
 	kfree(right_response);
 	shash_desc_zero(desc);
+	kfree(desc);
 
 	return rv;
 }
-- 
2.20.0