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 roberto.sassu@huawei.com Reviewed-by: Mimi Zohar zohar@linux.ibm.com --- 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 0d36259b690d..e4b47759ba1c 100644 --- a/security/integrity/evm/evm_main.c +++ b/security/integrity/evm/evm_main.c @@ -181,6 +181,12 @@ 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,