From 455b6c9112eff8d249e32ba165742085678a80a4 Mon Sep 17 00:00:00 2001 From: Roberto Sassu Date: Fri, 4 Sep 2020 11:23:30 +0200 Subject: [PATCH] evm: Check size of security.evm before using it 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: 5feeb61183dde ("evm: Allow non-SHA1 digital signatures") Signed-off-by: Roberto Sassu Signed-off-by: Mimi Zohar --- security/integrity/evm/evm_main.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c index 6ae00fee1d34..76d19146d74b 100644 --- a/security/integrity/evm/evm_main.c +++ b/security/integrity/evm/evm_main.c @@ -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,