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evm: Check size of security.evm before using it

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This patch checks the size for the EVM_IMA_XATTR_DIGSIG and
EVM_XATTR_PORTABLE_DIGSIG types to ensure that the algorithm is read from
the buffer returned by vfs_getxattr_alloc().

Cc: stable@vger.kernel.org # 4.19.x
Fixes: 5feeb61183 ("evm: Allow non-SHA1 digital signatures")
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
This commit is contained in:
Roberto Sassu 2020-09-04 11:23:30 +02:00 committed by Mimi Zohar
parent 4be92db3b5
commit 455b6c9112
1 changed files with 6 additions and 0 deletions
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6
security/integrity/evm/evm_main.c
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@ -184,6 +184,12 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
break;
case EVM_IMA_XATTR_DIGSIG:
case EVM_XATTR_PORTABLE_DIGSIG:
/* accept xattr with non-empty signature field */
if (xattr_len <= sizeof(struct signature_v2_hdr)) {
evm_status = INTEGRITY_FAIL;
goto out;
}
hdr = (struct signature_v2_hdr *)xattr_data;
digest.hdr.algo = hdr->hash_algo;
rc = evm_calc_hash(dentry, xattr_name, xattr_value,