From: Dan Carpenter <dan.carpenter@oracle.com>
To: roberto.sassu@huawei.com
Cc: linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org
Subject: [bug report] evm: Check also if *tfm is an error pointer in init_desc()
Date: Tue, 12 May 2020 13:48:09 +0300 [thread overview]
Message-ID: <20200512104809.GA262740@mwanda> (raw)
Hello Roberto Sassu,
The patch 53de3b080d5e: "evm: Check also if *tfm is an error pointer
in init_desc()" from Apr 27, 2020, leads to the following static
checker warning:
security/integrity/evm/evm_crypto.c:119 init_desc()
error: '*tfm' dereferencing possible ERR_PTR()
security/integrity/evm/evm_crypto.c
89
90 tfm = &evm_tfm[hash_algo];
91 algo = hash_algo_name[hash_algo];
92 }
93
94 if (IS_ERR_OR_NULL(*tfm)) {
This used to be a "if (!*tfm)" check.
95 mutex_lock(&mutex);
96 if (*tfm)
97 goto out;
Then we test again with the lock held. But in the new code if "*tfm"
is an error pointer then we jump directly to the unlock and crash on the
next line. I can't see how the commit would fix anything.
98 *tfm = crypto_alloc_shash(algo, 0, CRYPTO_NOLOAD);
99 if (IS_ERR(*tfm)) {
100 rc = PTR_ERR(*tfm);
101 pr_err("Can not allocate %s (reason: %ld)\n", algo, rc);
102 *tfm = NULL;
103 mutex_unlock(&mutex);
104 return ERR_PTR(rc);
105 }
106 if (type == EVM_XATTR_HMAC) {
107 rc = crypto_shash_setkey(*tfm, evmkey, evmkey_len);
108 if (rc) {
109 crypto_free_shash(*tfm);
110 *tfm = NULL;
111 mutex_unlock(&mutex);
112 return ERR_PTR(rc);
113 }
114 }
115 out:
116 mutex_unlock(&mutex);
117 }
118
119 desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),
^^^^
I don't understand how using *tfm outside of a lock is safe at all
anyway.
120 GFP_KERNEL);
121 if (!desc)
122 return ERR_PTR(-ENOMEM);
123
regards,
dan carpenter
next reply other threads:[~2020-05-12 10:51 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-12 10:48 Dan Carpenter [this message]
2020-05-12 11:31 ` [bug report] evm: Check also if *tfm is an error pointer in init_desc() Roberto Sassu
2020-05-12 12:34 ` Dan Carpenter
2020-05-12 12:45 ` Roberto Sassu
2020-05-12 13:04 ` Dan Carpenter
2020-05-12 13:08 ` Roberto Sassu
2020-05-12 13:19 ` [PATCH] evm: Fix a small race " Dan Carpenter
2020-05-12 13:43 ` Roberto Sassu
2020-05-12 17:47 ` [PATCH v2] " Dan Carpenter
2020-05-14 6:47 ` Roberto Sassu
2020-05-14 7:11 ` Krzysztof Struczynski
2020-05-14 18:21 ` Mimi Zohar
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