linux/security/apparmor/resource.c
Jeff Mahoney ff118479a7 apparmor: allow SYS_CAP_RESOURCE to be sufficient to prlimit another task
While using AppArmor, SYS_CAP_RESOURCE is insufficient to call prlimit
on another task. The only other example of a AppArmor mediating access to
another, already running, task (ignoring fork+exec) is ptrace.

The AppArmor model for ptrace is that one of the following must be true:
1) The tracer is unconfined
2) The tracer is in complain mode
3) The tracer and tracee are confined by the same profile
4) The tracer is confined but has SYS_CAP_PTRACE

1), 2, and 3) are already true for setrlimit.

We can match the ptrace model just by allowing CAP_SYS_RESOURCE.

We still test the values of the rlimit since it can always be overridden
using a value that means unlimited for a particular resource.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
2016-07-12 08:43:10 -07:00

157 lines
4.4 KiB
C

/*
* AppArmor security module
*
* This file contains AppArmor resource mediation and attachment
*
* Copyright (C) 1998-2008 Novell/SUSE
* Copyright 2009-2010 Canonical Ltd.
*
* 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.
*/
#include <linux/audit.h>
#include "include/audit.h"
#include "include/context.h"
#include "include/resource.h"
#include "include/policy.h"
/*
* Table of rlimit names: we generate it from resource.h.
*/
#include "rlim_names.h"
struct aa_fs_entry aa_fs_entry_rlimit[] = {
AA_FS_FILE_STRING("mask", AA_FS_RLIMIT_MASK),
{ }
};
/* audit callback for resource specific fields */
static void audit_cb(struct audit_buffer *ab, void *va)
{
struct common_audit_data *sa = va;
audit_log_format(ab, " rlimit=%s value=%lu",
rlim_names[sa->aad->rlim.rlim], sa->aad->rlim.max);
}
/**
* audit_resource - audit setting resource limit
* @profile: profile being enforced (NOT NULL)
* @resoure: rlimit being auditing
* @value: value being set
* @error: error value
*
* Returns: 0 or sa->error else other error code on failure
*/
static int audit_resource(struct aa_profile *profile, unsigned int resource,
unsigned long value, int error)
{
struct common_audit_data sa;
struct apparmor_audit_data aad = {0,};
sa.type = LSM_AUDIT_DATA_NONE;
sa.aad = &aad;
aad.op = OP_SETRLIMIT,
aad.rlim.rlim = resource;
aad.rlim.max = value;
aad.error = error;
return aa_audit(AUDIT_APPARMOR_AUTO, profile, GFP_KERNEL, &sa,
audit_cb);
}
/**
* aa_map_resouce - map compiled policy resource to internal #
* @resource: flattened policy resource number
*
* Returns: resource # for the current architecture.
*
* rlimit resource can vary based on architecture, map the compiled policy
* resource # to the internal representation for the architecture.
*/
int aa_map_resource(int resource)
{
return rlim_map[resource];
}
/**
* aa_task_setrlimit - test permission to set an rlimit
* @profile - profile confining the task (NOT NULL)
* @task - task the resource is being set on
* @resource - the resource being set
* @new_rlim - the new resource limit (NOT NULL)
*
* Control raising the processes hard limit.
*
* Returns: 0 or error code if setting resource failed
*/
int aa_task_setrlimit(struct aa_profile *profile, struct task_struct *task,
unsigned int resource, struct rlimit *new_rlim)
{
struct aa_profile *task_profile;
int error = 0;
rcu_read_lock();
task_profile = aa_get_profile(aa_cred_profile(__task_cred(task)));
rcu_read_unlock();
/* TODO: extend resource control to handle other (non current)
* profiles. AppArmor rules currently have the implicit assumption
* that the task is setting the resource of a task confined with
* the same profile or that the task setting the resource of another
* task has CAP_SYS_RESOURCE.
*/
if ((profile != task_profile &&
aa_capable(profile, CAP_SYS_RESOURCE, 1)) ||
(profile->rlimits.mask & (1 << resource) &&
new_rlim->rlim_max > profile->rlimits.limits[resource].rlim_max))
error = -EACCES;
aa_put_profile(task_profile);
return audit_resource(profile, resource, new_rlim->rlim_max, error);
}
/**
* __aa_transition_rlimits - apply new profile rlimits
* @old: old profile on task (NOT NULL)
* @new: new profile with rlimits to apply (NOT NULL)
*/
void __aa_transition_rlimits(struct aa_profile *old, struct aa_profile *new)
{
unsigned int mask = 0;
struct rlimit *rlim, *initrlim;
int i;
/* for any rlimits the profile controlled reset the soft limit
* to the less of the tasks hard limit and the init tasks soft limit
*/
if (old->rlimits.mask) {
for (i = 0, mask = 1; i < RLIM_NLIMITS; i++, mask <<= 1) {
if (old->rlimits.mask & mask) {
rlim = current->signal->rlim + i;
initrlim = init_task.signal->rlim + i;
rlim->rlim_cur = min(rlim->rlim_max,
initrlim->rlim_cur);
}
}
}
/* set any new hard limits as dictated by the new profile */
if (!new->rlimits.mask)
return;
for (i = 0, mask = 1; i < RLIM_NLIMITS; i++, mask <<= 1) {
if (!(new->rlimits.mask & mask))
continue;
rlim = current->signal->rlim + i;
rlim->rlim_max = min(rlim->rlim_max,
new->rlimits.limits[i].rlim_max);
/* soft limit should not exceed hard limit */
rlim->rlim_cur = min(rlim->rlim_cur, rlim->rlim_max);
}
}