linux-kernel - [PATCH 4.19 096/118] crypto: do not free algorithm before using

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Date:   Tue, 11 Dec 2018 16:41:55 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Pan Bian <bianpan2016@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>
Subject: [PATCH 4.19 096/118] crypto: do not free algorithm before using

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Pan Bian <bianpan2016@....com>

commit e5bde04ccce64d808f8b00a489a1fe5825d285cb upstream.

In multiple functions, the algorithm fields are read after its reference
is dropped through crypto_mod_put. In this case, the algorithm memory
may be freed, resulting in use-after-free bugs. This patch delays the
put operation until the algorithm is never used.

Fixes: 79c65d179a40 ("crypto: cbc - Convert to skcipher")
Fixes: a7d85e06ed80 ("crypto: cfb - add support for Cipher FeedBack mode")
Fixes: 043a44001b9e ("crypto: pcbc - Convert to skcipher")
Cc: <stable@...r.kernel.org>
Signed-off-by: Pan Bian <bianpan2016@....com>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 crypto/cbc.c  |    6 ++++--
 crypto/cfb.c  |    6 ++++--
 crypto/pcbc.c |    6 ++++--
 3 files changed, 12 insertions(+), 6 deletions(-)

--- a/crypto/cbc.c
+++ b/crypto/cbc.c
@@ -140,9 +140,8 @@ static int crypto_cbc_create(struct cryp
 	spawn = skcipher_instance_ctx(inst);
 	err = crypto_init_spawn(spawn, alg, skcipher_crypto_instance(inst),
 				CRYPTO_ALG_TYPE_MASK);
-	crypto_mod_put(alg);
 	if (err)
-		goto err_free_inst;
+		goto err_put_alg;
 
 	err = crypto_inst_setname(skcipher_crypto_instance(inst), "cbc", alg);
 	if (err)
@@ -174,12 +173,15 @@ static int crypto_cbc_create(struct cryp
 	err = skcipher_register_instance(tmpl, inst);
 	if (err)
 		goto err_drop_spawn;
+	crypto_mod_put(alg);
 
 out:
 	return err;
 
 err_drop_spawn:
 	crypto_drop_spawn(spawn);
+err_put_alg:
+	crypto_mod_put(alg);
 err_free_inst:
 	kfree(inst);
 	goto out;
--- a/crypto/cfb.c
+++ b/crypto/cfb.c
@@ -286,9 +286,8 @@ static int crypto_cfb_create(struct cryp
 	spawn = skcipher_instance_ctx(inst);
 	err = crypto_init_spawn(spawn, alg, skcipher_crypto_instance(inst),
 				CRYPTO_ALG_TYPE_MASK);
-	crypto_mod_put(alg);
 	if (err)
-		goto err_free_inst;
+		goto err_put_alg;
 
 	err = crypto_inst_setname(skcipher_crypto_instance(inst), "cfb", alg);
 	if (err)
@@ -317,12 +316,15 @@ static int crypto_cfb_create(struct cryp
 	err = skcipher_register_instance(tmpl, inst);
 	if (err)
 		goto err_drop_spawn;
+	crypto_mod_put(alg);
 
 out:
 	return err;
 
 err_drop_spawn:
 	crypto_drop_spawn(spawn);
+err_put_alg:
+	crypto_mod_put(alg);
 err_free_inst:
 	kfree(inst);
 	goto out;
--- a/crypto/pcbc.c
+++ b/crypto/pcbc.c
@@ -244,9 +244,8 @@ static int crypto_pcbc_create(struct cry
 	spawn = skcipher_instance_ctx(inst);
 	err = crypto_init_spawn(spawn, alg, skcipher_crypto_instance(inst),
 				CRYPTO_ALG_TYPE_MASK);
-	crypto_mod_put(alg);
 	if (err)
-		goto err_free_inst;
+		goto err_put_alg;
 
 	err = crypto_inst_setname(skcipher_crypto_instance(inst), "pcbc", alg);
 	if (err)
@@ -275,12 +274,15 @@ static int crypto_pcbc_create(struct cry
 	err = skcipher_register_instance(tmpl, inst);
 	if (err)
 		goto err_drop_spawn;
+	crypto_mod_put(alg);
 
 out:
 	return err;
 
 err_drop_spawn:
 	crypto_drop_spawn(spawn);
+err_put_alg:
+	crypto_mod_put(alg);
 err_free_inst:
 	kfree(inst);
 	goto out;