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Subject[PATCH] crypto: do not free algorithm before using
Date
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.

Signed-off-by: Pan Bian <bianpan2016@163.com>
---
crypto/cbc.c | 6 ++++--
crypto/cfb.c | 6 ++++--
crypto/pcbc.c | 6 ++++--
3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/crypto/cbc.c b/crypto/cbc.c
index b761b1f..dd5f332 100644
--- a/crypto/cbc.c
+++ b/crypto/cbc.c
@@ -140,9 +140,8 @@ static int crypto_cbc_create(struct crypto_template *tmpl, struct rtattr **tb)
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 crypto_template *tmpl, struct rtattr **tb)
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;
diff --git a/crypto/cfb.c b/crypto/cfb.c
index a0d68c0..20987d0 100644
--- a/crypto/cfb.c
+++ b/crypto/cfb.c
@@ -286,9 +286,8 @@ static int crypto_cfb_create(struct crypto_template *tmpl, struct rtattr **tb)
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 crypto_template *tmpl, struct rtattr **tb)
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;
diff --git a/crypto/pcbc.c b/crypto/pcbc.c
index ef802f6..8aa1014 100644
--- a/crypto/pcbc.c
+++ b/crypto/pcbc.c
@@ -244,9 +244,8 @@ static int crypto_pcbc_create(struct crypto_template *tmpl, struct rtattr **tb)
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 crypto_template *tmpl, struct rtattr **tb)
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;
--
2.7.4

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