Commit dcc47a02 authored by Herbert Xu's avatar Herbert Xu
Browse files

crypto: null - Use spin lock instead of mutex 



As the null algorithm may be freed in softirq context through
af_alg, use spin locks instead of mutexes to protect the default
null algorithm.

Reported-by: default avatar <syzbot+b3e02953598f447d4d2a@syzkaller.appspotmail.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 1047e21a

crypto/crypto_null.c

+26 −13
Original line number Diff line number Diff line
@@ -17,10 +17,10 @@ 
#include <crypto/internal/skcipher.h>

#include <linux/init.h>

#include <linux/module.h>

#include <linux/mm.h>

#include <linux/spinlock.h>

#include <linux/string.h>



static DEFINE_MUTEX(crypto_default_null_skcipher_lock);

static DEFINE_SPINLOCK(crypto_default_null_skcipher_lock);

static struct crypto_sync_skcipher *crypto_default_null_skcipher;

static int crypto_default_null_skcipher_refcnt;
@@ -152,23 +152,32 @@ MODULE_ALIAS_CRYPTO("cipher_null"); 


struct crypto_sync_skcipher *crypto_get_default_null_skcipher(void)

{

	struct crypto_sync_skcipher *ntfm = NULL;

	struct crypto_sync_skcipher *tfm;



	mutex_lock(&crypto_default_null_skcipher_lock);

	spin_lock_bh(&crypto_default_null_skcipher_lock);

	tfm = crypto_default_null_skcipher;



	if (!tfm) {

		tfm = crypto_alloc_sync_skcipher("ecb(cipher_null)", 0, 0);

		if (IS_ERR(tfm))

			goto unlock;

		spin_unlock_bh(&crypto_default_null_skcipher_lock);



		ntfm = crypto_alloc_sync_skcipher("ecb(cipher_null)", 0, 0);

		if (IS_ERR(ntfm))

			return ntfm;



		spin_lock_bh(&crypto_default_null_skcipher_lock);

		tfm = crypto_default_null_skcipher;

		if (!tfm) {

			tfm = ntfm;

			ntfm = NULL;

			crypto_default_null_skcipher = tfm;

		}

	}



	crypto_default_null_skcipher_refcnt++;

	spin_unlock_bh(&crypto_default_null_skcipher_lock);



unlock:

	mutex_unlock(&crypto_default_null_skcipher_lock);

	crypto_free_sync_skcipher(ntfm);



	return tfm;

}
@@ -176,12 +185,16 @@ EXPORT_SYMBOL_GPL(crypto_get_default_null_skcipher); 


void crypto_put_default_null_skcipher(void)

{

	mutex_lock(&crypto_default_null_skcipher_lock);

	struct crypto_sync_skcipher *tfm = NULL;



	spin_lock_bh(&crypto_default_null_skcipher_lock);

	if (!--crypto_default_null_skcipher_refcnt) {

		crypto_free_sync_skcipher(crypto_default_null_skcipher);

		tfm = crypto_default_null_skcipher;

		crypto_default_null_skcipher = NULL;

	}

	mutex_unlock(&crypto_default_null_skcipher_lock);

	spin_unlock_bh(&crypto_default_null_skcipher_lock);



	crypto_free_sync_skcipher(tfm);

}

EXPORT_SYMBOL_GPL(crypto_put_default_null_skcipher);