From: Dan Carpenter dan.carpenter@oracle.com
mainline inclusion from mainline-v5.7-rc7 commit 8433856947217ebb5697a8ff9c4c9cad4639a2cf category: bugfix
---------------------------
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.
Note: CRYPTO_ALG_ASYNC has been preserved since commit 3d234b3313cd1 ("crypto: drop mask=CRYPTO_ALG_ASYNC from 'shash' tfm allocations") is not applied to stable kernels.
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 --- security/integrity/evm/evm_crypto.c | 45 ++++++++++++++--------------- 1 file changed, 22 insertions(+), 23 deletions(-)
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c index d6b65b237840..157efcc3ad6e 100644 --- a/security/integrity/evm/evm_crypto.c +++ b/security/integrity/evm/evm_crypto.c @@ -78,7 +78,7 @@ 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) { @@ -96,32 +96,31 @@ 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_ALG_ASYNC | 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_ALG_ASYNC | 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)