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
>
> 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@xxxxxxxxxx>
> ---
> 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;
> }
>
