5.4-stable review patch. If anyone has any objections, please let me know.
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From: Herbert Xu herbert@gondor.apana.org.au
[ Upstream commit dcc47a028c24e793ce6d6efebfef1a1e92f80297 ]
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: syzbot+b3e02953598f447d4d2a@syzkaller.appspotmail.com Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Sasha Levin sashal@kernel.org --- crypto/crypto_null.c | 39 ++++++++++++++++++++++++++------------- 1 file changed, 26 insertions(+), 13 deletions(-)
diff --git a/crypto/crypto_null.c b/crypto/crypto_null.c index 5b84b0f7cc178..3378670286535 100644 --- a/crypto/crypto_null.c +++ b/crypto/crypto_null.c @@ -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; - - crypto_default_null_skcipher = tfm; + 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);