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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: Roberto Sassu <roberto.sassu@polito.it>
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
This commit is contained in:
Mimi Zohar 2011-05-13 12:53:38 -04:00
parent 7102ebcd65
commit 817b54aa45
3 changed files with 27 additions and 1 deletions
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6
include/linux/evm.h
View File

@ -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;

15
security/integrity/evm/evm_main.c
View File

@ -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

7
security/security.c
View File

@ -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);