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authorDan Carpenter <dan.carpenter@oracle.com>2020-05-12 16:19:17 +0300
committerMimi Zohar <zohar@linux.ibm.com>2020-05-15 02:55:54 +0300
commit8433856947217ebb5697a8ff9c4c9cad4639a2cf (patch)
treec85e552f9a199f1996efbd103abebf6dd52cbc63 /security
parent770f60586d2af0590be263f55fd079226313922c (diff)
downloadlinux-8433856947217ebb5697a8ff9c4c9cad4639a2cf.tar.xz
evm: Fix a small race in init_desc()
The IS_ERR_OR_NULL() function has two conditions and if we got really unlucky we could hit a race where "ptr" started as an error pointer and then was set to NULL. Both conditions would be false even though the pointer at the end was NULL. This patch fixes the problem by ensuring that "*tfm" can only be NULL or valid. I have introduced a "tmp_tfm" variable to make that work. I also reversed a condition and pulled the code in one tab. Reported-by: Roberto Sassu <roberto.sassu@huawei.com> Fixes: 53de3b080d5e ("evm: Check also if *tfm is an error pointer in init_desc()") Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Acked-by: Roberto Sassu <roberto.sassu@huawei.com> Acked-by: Krzysztof Struczynski <krzysztof.struczynski@huawei.com> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Diffstat (limited to 'security')
-rw-r--r--security/integrity/evm/evm_crypto.c44
1 files changed, 22 insertions, 22 deletions
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index 2e1597e59606..764b896cd628 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -73,7 +73,7 @@ static struct shash_desc *init_desc(char type, uint8_t hash_algo)
{
long rc;
const char *algo;
- struct crypto_shash **tfm;
+ struct crypto_shash **tfm, *tmp_tfm;
struct shash_desc *desc;
if (type == EVM_XATTR_HMAC) {
@@ -91,31 +91,31 @@ static struct shash_desc *init_desc(char type, uint8_t hash_algo)
algo = hash_algo_name[hash_algo];
}
- if (IS_ERR_OR_NULL(*tfm)) {
- mutex_lock(&mutex);
- if (*tfm)
- goto out;
- *tfm = crypto_alloc_shash(algo, 0, CRYPTO_NOLOAD);
- if (IS_ERR(*tfm)) {
- rc = PTR_ERR(*tfm);
- pr_err("Can not allocate %s (reason: %ld)\n", algo, rc);
- *tfm = NULL;
+ if (*tfm)
+ goto alloc;
+ mutex_lock(&mutex);
+ if (*tfm)
+ goto unlock;
+
+ tmp_tfm = crypto_alloc_shash(algo, 0, CRYPTO_NOLOAD);
+ if (IS_ERR(tmp_tfm)) {
+ pr_err("Can not allocate %s (reason: %ld)\n", algo,
+ PTR_ERR(tmp_tfm));
+ mutex_unlock(&mutex);
+ return ERR_CAST(tmp_tfm);
+ }
+ if (type == EVM_XATTR_HMAC) {
+ rc = crypto_shash_setkey(tmp_tfm, evmkey, evmkey_len);
+ if (rc) {
+ crypto_free_shash(tmp_tfm);
mutex_unlock(&mutex);
return ERR_PTR(rc);
}
- if (type == EVM_XATTR_HMAC) {
- rc = crypto_shash_setkey(*tfm, evmkey, evmkey_len);
- if (rc) {
- crypto_free_shash(*tfm);
- *tfm = NULL;
- mutex_unlock(&mutex);
- return ERR_PTR(rc);
- }
- }
-out:
- mutex_unlock(&mutex);
}
-
+ *tfm = tmp_tfm;
+unlock:
+ mutex_unlock(&mutex);
+alloc:
desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm),
GFP_KERNEL);
if (!desc)