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ecryptfs: avoid ctx initialization race

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It might be possible for two callers to race the mutex lock after the
NULL ctx check. Instead, move the lock above the check so there isn't
the possibility of leaking a crypto ctx. Additionally, report the full
algo name when failing.

Signed-off-by: Kees Cook <keescook@chromium.org>
[tyhicks: remove out label, which is no longer used]
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
This commit is contained in:
Kees Cook 2013-08-13 15:02:27 -07:00 committed by Tyler Hicks
parent e6cbd6a44d
commit cb69f36ba1
1 changed files with 6 additions and 6 deletions
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12
fs/ecryptfs/crypto.c
View file

@ -614,30 +614,30 @@ int ecryptfs_init_crypt_ctx(struct ecryptfs_crypt_stat *crypt_stat)
"key_size_bits = [%zd]\n",
crypt_stat->cipher, (int)strlen(crypt_stat->cipher),
crypt_stat->key_size << 3);
mutex_lock(&crypt_stat->cs_tfm_mutex);
if (crypt_stat->tfm) {
rc = 0;
goto out;
goto out_unlock;
}
mutex_lock(&crypt_stat->cs_tfm_mutex);
rc = ecryptfs_crypto_api_algify_cipher_name(&full_alg_name,
crypt_stat->cipher, "cbc");
if (rc)
goto out_unlock;
crypt_stat->tfm = crypto_alloc_ablkcipher(full_alg_name, 0, 0);
kfree(full_alg_name);
if (IS_ERR(crypt_stat->tfm)) {
rc = PTR_ERR(crypt_stat->tfm);
crypt_stat->tfm = NULL;
ecryptfs_printk(KERN_ERR, "cryptfs: init_crypt_ctx(): "
"Error initializing cipher [%s]\n",
crypt_stat->cipher);
goto out_unlock;
full_alg_name);
goto out_free;
}
crypto_ablkcipher_set_flags(crypt_stat->tfm, CRYPTO_TFM_REQ_WEAK_KEY);
rc = 0;
out_free:
kfree(full_alg_name);
out_unlock:
mutex_unlock(&crypt_stat->cs_tfm_mutex);
out:
return rc;
}