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linux-next/security/integrity/ima/ima_api.c
Roberto Sassu 45fae74939 ima: free duplicate measurement memory
Info about new measurements are cached in the iint for performance.  When
the inode is flushed from cache, the associated iint is flushed as well.
Subsequent access to the inode will cause the inode to be re-measured and
will attempt to add a duplicate entry to the measurement list.

This patch frees the duplicate measurement memory, fixing a memory leak.

Signed-off-by: Roberto Sassu <roberto.sassu@polito.it>
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Cc: stable@vger.kernel.org
2011-12-19 22:04:32 -05:00

186 lines
5.5 KiB
C

/*
* Copyright (C) 2008 IBM Corporation
*
* Author: Mimi Zohar <zohar@us.ibm.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation, version 2 of the
* License.
*
* File: ima_api.c
* Implements must_measure, collect_measurement, store_measurement,
* and store_template.
*/
#include <linux/module.h>
#include <linux/slab.h>
#include "ima.h"
static const char *IMA_TEMPLATE_NAME = "ima";
/*
* ima_store_template - store ima template measurements
*
* Calculate the hash of a template entry, add the template entry
* to an ordered list of measurement entries maintained inside the kernel,
* and also update the aggregate integrity value (maintained inside the
* configured TPM PCR) over the hashes of the current list of measurement
* entries.
*
* Applications retrieve the current kernel-held measurement list through
* the securityfs entries in /sys/kernel/security/ima. The signed aggregate
* TPM PCR (called quote) can be retrieved using a TPM user space library
* and is used to validate the measurement list.
*
* Returns 0 on success, error code otherwise
*/
int ima_store_template(struct ima_template_entry *entry,
int violation, struct inode *inode)
{
const char *op = "add_template_measure";
const char *audit_cause = "hashing_error";
int result;
memset(entry->digest, 0, sizeof(entry->digest));
entry->template_name = IMA_TEMPLATE_NAME;
entry->template_len = sizeof(entry->template);
if (!violation) {
result = ima_calc_template_hash(entry->template_len,
&entry->template,
entry->digest);
if (result < 0) {
integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
entry->template_name, op,
audit_cause, result, 0);
return result;
}
}
result = ima_add_template_entry(entry, violation, op, inode);
return result;
}
/*
* ima_add_violation - add violation to measurement list.
*
* Violations are flagged in the measurement list with zero hash values.
* By extending the PCR with 0xFF's instead of with zeroes, the PCR
* value is invalidated.
*/
void ima_add_violation(struct inode *inode, const unsigned char *filename,
const char *op, const char *cause)
{
struct ima_template_entry *entry;
int violation = 1;
int result;
/* can overflow, only indicator */
atomic_long_inc(&ima_htable.violations);
entry = kmalloc(sizeof(*entry), GFP_KERNEL);
if (!entry) {
result = -ENOMEM;
goto err_out;
}
memset(&entry->template, 0, sizeof(entry->template));
strncpy(entry->template.file_name, filename, IMA_EVENT_NAME_LEN_MAX);
result = ima_store_template(entry, violation, inode);
if (result < 0)
kfree(entry);
err_out:
integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
op, cause, result, 0);
}
/**
* ima_must_measure - measure decision based on policy.
* @inode: pointer to inode to measure
* @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXECUTE)
* @function: calling function (FILE_CHECK, BPRM_CHECK, FILE_MMAP)
*
* The policy is defined in terms of keypairs:
* subj=, obj=, type=, func=, mask=, fsmagic=
* subj,obj, and type: are LSM specific.
* func: FILE_CHECK | BPRM_CHECK | FILE_MMAP
* mask: contains the permission mask
* fsmagic: hex value
*
* Return 0 to measure. For matching a DONT_MEASURE policy, no policy,
* or other error, return an error code.
*/
int ima_must_measure(struct inode *inode, int mask, int function)
{
int must_measure;
must_measure = ima_match_policy(inode, function, mask);
return must_measure ? 0 : -EACCES;
}
/*
* ima_collect_measurement - collect file measurement
*
* Calculate the file hash, if it doesn't already exist,
* storing the measurement and i_version in the iint.
*
* Must be called with iint->mutex held.
*
* Return 0 on success, error code otherwise
*/
int ima_collect_measurement(struct integrity_iint_cache *iint,
struct file *file)
{
int result = -EEXIST;
if (!(iint->flags & IMA_MEASURED)) {
u64 i_version = file->f_dentry->d_inode->i_version;
memset(iint->digest, 0, IMA_DIGEST_SIZE);
result = ima_calc_hash(file, iint->digest);
if (!result)
iint->version = i_version;
}
return result;
}
/*
* ima_store_measurement - store file measurement
*
* Create an "ima" template and then store the template by calling
* ima_store_template.
*
* We only get here if the inode has not already been measured,
* but the measurement could already exist:
* - multiple copies of the same file on either the same or
* different filesystems.
* - the inode was previously flushed as well as the iint info,
* containing the hashing info.
*
* Must be called with iint->mutex held.
*/
void ima_store_measurement(struct integrity_iint_cache *iint,
struct file *file, const unsigned char *filename)
{
const char *op = "add_template_measure";
const char *audit_cause = "ENOMEM";
int result = -ENOMEM;
struct inode *inode = file->f_dentry->d_inode;
struct ima_template_entry *entry;
int violation = 0;
entry = kmalloc(sizeof(*entry), GFP_KERNEL);
if (!entry) {
integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
op, audit_cause, result, 0);
return;
}
memset(&entry->template, 0, sizeof(entry->template));
memcpy(entry->template.digest, iint->digest, IMA_DIGEST_SIZE);
strncpy(entry->template.file_name, filename, IMA_EVENT_NAME_LEN_MAX);
result = ima_store_template(entry, violation, inode);
if (!result || result == -EEXIST)
iint->flags |= IMA_MEASURED;
if (result < 0)
kfree(entry);
}