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Commit 817b54aa authored by Mimi Zohar's avatar Mimi Zohar
Browse files

evm: add evm_inode_setattr to prevent updating an invalid security.evm 



Permit changing of security.evm only when valid, unless in fixmode.

Reported-by: default avatarRoberto Sassu <roberto.sassu@polito.it>
Signed-off-by: default avatarMimi Zohar <zohar@us.ibm.com>
parent 7102ebcd

include/linux/evm.h

+6 −0
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ extern enum integrity_status evm_verifyxattr(struct dentry *dentry, 
					     void *xattr_value,

					     size_t xattr_value_len,

					     struct integrity_iint_cache *iint);

extern int evm_inode_setattr(struct dentry *dentry, struct iattr *attr);

extern void evm_inode_post_setattr(struct dentry *dentry, int ia_valid);

extern int evm_inode_setxattr(struct dentry *dentry, const char *name,

			      const void *value, size_t size);
@@ -44,6 +45,11 @@ static inline enum integrity_status evm_verifyxattr(struct dentry *dentry, 
}

#endif



static int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)

{

	return 0;

}



static inline void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)

{

	return;

security/integrity/evm/evm_main.c

+15 −0
Original line number Diff line number Diff line
@@ -277,6 +277,21 @@ void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name) 
	return;

}



/**

 * evm_inode_setattr - prevent updating an invalid EVM extended attribute

 * @dentry: pointer to the affected dentry

 */

int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)

{

	unsigned int ia_valid = attr->ia_valid;

	enum integrity_status evm_status;



	if (ia_valid & ~(ATTR_MODE | ATTR_UID | ATTR_GID))

		return 0;

	evm_status = evm_verify_current_integrity(dentry);

	return evm_status == INTEGRITY_PASS ? 0 : -EPERM;

}



/**

 * evm_inode_post_setattr - update 'security.evm' after modifying metadata

 * @dentry: pointer to the affected dentry

security/security.c

+6 −1
Original line number Diff line number Diff line
@@ -571,9 +571,14 @@ int security_inode_exec_permission(struct inode *inode, unsigned int flags) 


int security_inode_setattr(struct dentry *dentry, struct iattr *attr)

{

	int ret;



	if (unlikely(IS_PRIVATE(dentry->d_inode)))

		return 0;

	return security_ops->inode_setattr(dentry, attr);

	ret = security_ops->inode_setattr(dentry, attr);

	if (ret)

		return ret;

	return evm_inode_setattr(dentry, attr);

}

EXPORT_SYMBOL_GPL(security_inode_setattr);