Re: [PATCH -next] evm: Use __vfs_setxattr() to update security.evm
From: Mimi Zohar <zohar@linux.ibm.com>
Date: 2023-01-18 21:45:28
Also in:
linux-integrity, lkml
On Wed, 2022-12-28 at 11:02 +0800, Xiu Jianfeng wrote:
Currently it uses __vfs_setxattr_noperm() to update "security.evm", however there are two lsm hooks(inode_post_setxattr and inode_setsecurity) being called inside this function, which don't make any sense for xattr "security.evm", because the handlers of these two hooks, such as selinux and smack, only care about their own xattr.
Updating the security.ima hash triggers re-calculating and writing the security.evm HMAC. Refer to evm_inode_post_setxattr(). Mimi
quoted hunk ↗ jump to hunk
On the other hand, there is a literally rather than actually cyclical callchain as follows: security_inode_post_setxattr ->evm_inode_post_setxattr ->evm_update_evmxattr ->__vfs_setxattr_noperm ->security_inode_post_setxattr So use __vfs_setxattr() to update "security.evm". Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com> --- security/integrity/evm/evm_crypto.c | 7 +++---- security/integrity/ima/ima_appraise.c | 8 ++++---- 2 files changed, 7 insertions(+), 8 deletions(-)diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c index fa5ff13fa8c9..d8275dfa49ef 100644 --- a/security/integrity/evm/evm_crypto.c +++ b/security/integrity/evm/evm_crypto.c@@ -376,10 +376,9 @@ int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name, xattr_value_len, &data); if (rc == 0) { data.hdr.xattr.sha1.type = EVM_XATTR_HMAC; - rc = __vfs_setxattr_noperm(&init_user_ns, dentry, - XATTR_NAME_EVM, - &data.hdr.xattr.data[1], - SHA1_DIGEST_SIZE + 1, 0); + rc = __vfs_setxattr(&init_user_ns, dentry, d_inode(dentry), + XATTR_NAME_EVM, &data.hdr.xattr.data[1], + SHA1_DIGEST_SIZE + 1, 0); } else if (rc == -ENODATA && (inode->i_opflags & IOP_XATTR)) { rc = __vfs_removexattr(&init_user_ns, dentry, XATTR_NAME_EVM); }diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c index ee6f7e237f2e..d2de9dc6c345 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c@@ -98,10 +98,10 @@ static int ima_fix_xattr(struct dentry *dentry, iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG; iint->ima_hash->xattr.ng.algo = algo; } - rc = __vfs_setxattr_noperm(&init_user_ns, dentry, XATTR_NAME_IMA, - &iint->ima_hash->xattr.data[offset], - (sizeof(iint->ima_hash->xattr) - offset) + - iint->ima_hash->length, 0); + rc = __vfs_setxattr(&init_user_ns, dentry, d_inode(dentry), + XATTR_NAME_IMA, &iint->ima_hash->xattr.data[offset], + (sizeof(iint->ima_hash->xattr) - offset) + + iint->ima_hash->length, 0); return rc; }