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Commit cb69f36b authored by Kees Cook's avatar Kees Cook Committed by Tyler Hicks
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ecryptfs: avoid ctx initialization race 



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: default avatarKees Cook <keescook@chromium.org>
[tyhicks: remove out label, which is no longer used]
Signed-off-by: default avatarTyler Hicks <tyhicks@canonical.com>
parent e6cbd6a4

fs/ecryptfs/crypto.c

+6 −6
Original line number Diff line number Diff line
@@ -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;

}