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

Greg Kroah-Hartman
2018-12-11T16:01:00Z

From: Pan Bian <bianpan2016@163.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@vger.kernel.org>
Signed-off-by: Pan Bian <bianpan2016@163.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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;