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339 lines
8.4 KiB
C
339 lines
8.4 KiB
C
/*
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* Copyright (C) 2005,2006,2007,2008 IBM Corporation
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*
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* Authors:
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* Reiner Sailer <sailer@watson.ibm.com>
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* Serge Hallyn <serue@us.ibm.com>
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* Kylene Hall <kylene@us.ibm.com>
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* Mimi Zohar <zohar@us.ibm.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, version 2 of the
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* License.
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*
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* File: ima_main.c
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* implements the IMA hooks: ima_bprm_check, ima_file_mmap,
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* and ima_file_check.
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*/
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#include <linux/module.h>
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#include <linux/file.h>
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#include <linux/binfmts.h>
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#include <linux/mount.h>
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#include <linux/mman.h>
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#include <linux/slab.h>
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#include "ima.h"
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int ima_initialized;
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char *ima_hash = "sha1";
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static int __init hash_setup(char *str)
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{
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if (strncmp(str, "md5", 3) == 0)
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ima_hash = "md5";
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return 1;
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}
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__setup("ima_hash=", hash_setup);
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struct ima_imbalance {
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struct hlist_node node;
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unsigned long fsmagic;
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};
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/*
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* ima_limit_imbalance - emit one imbalance message per filesystem type
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*
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* Maintain list of filesystem types that do not measure files properly.
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* Return false if unknown, true if known.
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*/
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static bool ima_limit_imbalance(struct file *file)
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{
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static DEFINE_SPINLOCK(ima_imbalance_lock);
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static HLIST_HEAD(ima_imbalance_list);
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struct super_block *sb = file->f_dentry->d_sb;
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struct ima_imbalance *entry;
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struct hlist_node *node;
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bool found = false;
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rcu_read_lock();
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hlist_for_each_entry_rcu(entry, node, &ima_imbalance_list, node) {
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if (entry->fsmagic == sb->s_magic) {
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found = true;
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break;
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}
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}
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rcu_read_unlock();
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if (found)
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goto out;
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entry = kmalloc(sizeof(*entry), GFP_NOFS);
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if (!entry)
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goto out;
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entry->fsmagic = sb->s_magic;
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spin_lock(&ima_imbalance_lock);
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/*
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* we could have raced and something else might have added this fs
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* to the list, but we don't really care
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*/
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hlist_add_head_rcu(&entry->node, &ima_imbalance_list);
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spin_unlock(&ima_imbalance_lock);
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printk(KERN_INFO "IMA: unmeasured files on fsmagic: %lX\n",
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entry->fsmagic);
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out:
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return found;
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}
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/* ima_read_write_check - reflect possible reading/writing errors in the PCR.
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*
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* When opening a file for read, if the file is already open for write,
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* the file could change, resulting in a file measurement error.
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*
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* Opening a file for write, if the file is already open for read, results
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* in a time of measure, time of use (ToMToU) error.
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*
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* In either case invalidate the PCR.
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*/
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enum iint_pcr_error { TOMTOU, OPEN_WRITERS };
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static void ima_read_write_check(enum iint_pcr_error error,
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struct ima_iint_cache *iint,
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struct inode *inode,
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const unsigned char *filename)
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{
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switch (error) {
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case TOMTOU:
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if (iint->readcount > 0)
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ima_add_violation(inode, filename, "invalid_pcr",
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"ToMToU");
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break;
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case OPEN_WRITERS:
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if (iint->writecount > 0)
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ima_add_violation(inode, filename, "invalid_pcr",
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"open_writers");
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break;
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}
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}
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/*
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* Update the counts given an fmode_t
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*/
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static void ima_inc_counts(struct ima_iint_cache *iint, fmode_t mode)
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{
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BUG_ON(!mutex_is_locked(&iint->mutex));
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iint->opencount++;
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if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
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iint->readcount++;
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if (mode & FMODE_WRITE)
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iint->writecount++;
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}
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/*
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* ima_counts_get - increment file counts
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*
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* Maintain read/write counters for all files, but only
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* invalidate the PCR for measured files:
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* - Opening a file for write when already open for read,
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* results in a time of measure, time of use (ToMToU) error.
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* - Opening a file for read when already open for write,
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* could result in a file measurement error.
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*
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*/
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void ima_counts_get(struct file *file)
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{
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struct dentry *dentry = file->f_path.dentry;
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struct inode *inode = dentry->d_inode;
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fmode_t mode = file->f_mode;
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struct ima_iint_cache *iint;
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int rc;
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if (!ima_initialized || !S_ISREG(inode->i_mode))
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return;
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iint = ima_iint_find_get(inode);
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if (!iint)
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return;
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mutex_lock(&iint->mutex);
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rc = ima_must_measure(iint, inode, MAY_READ, FILE_CHECK);
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if (rc < 0)
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goto out;
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if (mode & FMODE_WRITE) {
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ima_read_write_check(TOMTOU, iint, inode, dentry->d_name.name);
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goto out;
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}
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ima_read_write_check(OPEN_WRITERS, iint, inode, dentry->d_name.name);
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out:
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ima_inc_counts(iint, file->f_mode);
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mutex_unlock(&iint->mutex);
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kref_put(&iint->refcount, iint_free);
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}
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/*
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* Decrement ima counts
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*/
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static void ima_dec_counts(struct ima_iint_cache *iint, struct inode *inode,
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struct file *file)
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{
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mode_t mode = file->f_mode;
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BUG_ON(!mutex_is_locked(&iint->mutex));
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iint->opencount--;
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if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
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iint->readcount--;
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if (mode & FMODE_WRITE) {
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iint->writecount--;
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if (iint->writecount == 0) {
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if (iint->version != inode->i_version)
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iint->flags &= ~IMA_MEASURED;
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}
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}
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if (((iint->opencount < 0) ||
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(iint->readcount < 0) ||
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(iint->writecount < 0)) &&
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!ima_limit_imbalance(file)) {
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printk(KERN_INFO "%s: open/free imbalance (r:%ld w:%ld o:%ld)\n",
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__func__, iint->readcount, iint->writecount,
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iint->opencount);
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dump_stack();
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}
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}
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/**
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* ima_file_free - called on __fput()
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* @file: pointer to file structure being freed
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*
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* Flag files that changed, based on i_version;
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* and decrement the iint readcount/writecount.
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*/
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void ima_file_free(struct file *file)
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{
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struct inode *inode = file->f_dentry->d_inode;
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struct ima_iint_cache *iint;
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if (!ima_initialized || !S_ISREG(inode->i_mode))
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return;
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iint = ima_iint_find_get(inode);
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if (!iint)
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return;
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mutex_lock(&iint->mutex);
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ima_dec_counts(iint, inode, file);
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mutex_unlock(&iint->mutex);
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kref_put(&iint->refcount, iint_free);
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}
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static int process_measurement(struct file *file, const unsigned char *filename,
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int mask, int function)
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{
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struct inode *inode = file->f_dentry->d_inode;
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struct ima_iint_cache *iint;
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int rc;
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if (!ima_initialized || !S_ISREG(inode->i_mode))
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return 0;
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iint = ima_iint_find_get(inode);
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if (!iint)
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return -ENOMEM;
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mutex_lock(&iint->mutex);
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rc = ima_must_measure(iint, inode, mask, function);
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if (rc != 0)
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goto out;
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rc = ima_collect_measurement(iint, file);
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if (!rc)
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ima_store_measurement(iint, file, filename);
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out:
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mutex_unlock(&iint->mutex);
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kref_put(&iint->refcount, iint_free);
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return rc;
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}
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/**
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* ima_file_mmap - based on policy, collect/store measurement.
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* @file: pointer to the file to be measured (May be NULL)
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* @prot: contains the protection that will be applied by the kernel.
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*
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* Measure files being mmapped executable based on the ima_must_measure()
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* policy decision.
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*
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* Return 0 on success, an error code on failure.
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* (Based on the results of appraise_measurement().)
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*/
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int ima_file_mmap(struct file *file, unsigned long prot)
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{
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int rc;
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if (!file)
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return 0;
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if (prot & PROT_EXEC)
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rc = process_measurement(file, file->f_dentry->d_name.name,
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MAY_EXEC, FILE_MMAP);
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return 0;
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}
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/**
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* ima_bprm_check - based on policy, collect/store measurement.
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* @bprm: contains the linux_binprm structure
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*
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* The OS protects against an executable file, already open for write,
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* from being executed in deny_write_access() and an executable file,
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* already open for execute, from being modified in get_write_access().
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* So we can be certain that what we verify and measure here is actually
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* what is being executed.
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*
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* Return 0 on success, an error code on failure.
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* (Based on the results of appraise_measurement().)
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*/
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int ima_bprm_check(struct linux_binprm *bprm)
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{
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int rc;
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rc = process_measurement(bprm->file, bprm->filename,
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MAY_EXEC, BPRM_CHECK);
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return 0;
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}
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/**
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* ima_path_check - based on policy, collect/store measurement.
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* @file: pointer to the file to be measured
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* @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
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*
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* Measure files based on the ima_must_measure() policy decision.
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*
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* Always return 0 and audit dentry_open failures.
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* (Return code will be based upon measurement appraisal.)
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*/
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int ima_file_check(struct file *file, int mask)
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{
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int rc;
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rc = process_measurement(file, file->f_dentry->d_name.name,
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mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
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FILE_CHECK);
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return 0;
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}
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EXPORT_SYMBOL_GPL(ima_file_check);
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static int __init init_ima(void)
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{
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int error;
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error = ima_init();
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ima_initialized = 1;
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return error;
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}
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static void __exit cleanup_ima(void)
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{
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ima_cleanup();
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}
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late_initcall(init_ima); /* Start IMA after the TPM is available */
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MODULE_DESCRIPTION("Integrity Measurement Architecture");
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MODULE_LICENSE("GPL");
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