linux/security/apparmor/context.c
John Johansen 77b071b340 apparmor: change how profile replacement update is done
remove the use of replaced by chaining and move to profile invalidation
and lookup to handle task replacement.

Replacement chaining can result in large chains of profiles being pinned
in memory when one profile in the chain is use. With implicit labeling
this will be even more of a problem, so move to a direct lookup method.

Signed-off-by: John Johansen <john.johansen@canonical.com>
2013-08-14 11:42:06 -07:00

223 lines
5.4 KiB
C

/*
* AppArmor security module
*
* This file contains AppArmor functions used to manipulate object security
* contexts.
*
* 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.
*
*
* AppArmor sets confinement on every task, via the the aa_task_cxt and
* the aa_task_cxt.profile, both of which are required and are not allowed
* to be NULL. The aa_task_cxt is not reference counted and is unique
* to each cred (which is reference count). The profile pointed to by
* the task_cxt is reference counted.
*
* TODO
* If a task uses change_hat it currently does not return to the old
* cred or task context but instead creates a new one. Ideally the task
* should return to the previous cred if it has not been modified.
*
*/
#include "include/context.h"
#include "include/policy.h"
/**
* aa_alloc_task_context - allocate a new task_cxt
* @flags: gfp flags for allocation
*
* Returns: allocated buffer or NULL on failure
*/
struct aa_task_cxt *aa_alloc_task_context(gfp_t flags)
{
return kzalloc(sizeof(struct aa_task_cxt), flags);
}
/**
* aa_free_task_context - free a task_cxt
* @cxt: task_cxt to free (MAYBE NULL)
*/
void aa_free_task_context(struct aa_task_cxt *cxt)
{
if (cxt) {
aa_put_profile(cxt->profile);
aa_put_profile(cxt->previous);
aa_put_profile(cxt->onexec);
kzfree(cxt);
}
}
/**
* aa_dup_task_context - duplicate a task context, incrementing reference counts
* @new: a blank task context (NOT NULL)
* @old: the task context to copy (NOT NULL)
*/
void aa_dup_task_context(struct aa_task_cxt *new, const struct aa_task_cxt *old)
{
*new = *old;
aa_get_profile(new->profile);
aa_get_profile(new->previous);
aa_get_profile(new->onexec);
}
/**
* aa_get_task_profile - Get another task's profile
* @task: task to query (NOT NULL)
*
* Returns: counted reference to @task's profile
*/
struct aa_profile *aa_get_task_profile(struct task_struct *task)
{
struct aa_profile *p;
rcu_read_lock();
p = aa_get_profile(__aa_task_profile(task));
rcu_read_unlock();
return p;
}
/**
* aa_replace_current_profile - replace the current tasks profiles
* @profile: new profile (NOT NULL)
*
* Returns: 0 or error on failure
*/
int aa_replace_current_profile(struct aa_profile *profile)
{
struct aa_task_cxt *cxt = current_cxt();
struct cred *new;
BUG_ON(!profile);
if (cxt->profile == profile)
return 0;
new = prepare_creds();
if (!new)
return -ENOMEM;
cxt = cred_cxt(new);
if (unconfined(profile) || (cxt->profile->ns != profile->ns))
/* if switching to unconfined or a different profile namespace
* clear out context state
*/
aa_clear_task_cxt_trans(cxt);
/* be careful switching cxt->profile, when racing replacement it
* is possible that cxt->profile->replacedby->profile is the reference
* keeping @profile valid, so make sure to get its reference before
* dropping the reference on cxt->profile */
aa_get_profile(profile);
aa_put_profile(cxt->profile);
cxt->profile = profile;
commit_creds(new);
return 0;
}
/**
* aa_set_current_onexec - set the tasks change_profile to happen onexec
* @profile: system profile to set at exec (MAYBE NULL to clear value)
*
* Returns: 0 or error on failure
*/
int aa_set_current_onexec(struct aa_profile *profile)
{
struct aa_task_cxt *cxt;
struct cred *new = prepare_creds();
if (!new)
return -ENOMEM;
cxt = cred_cxt(new);
aa_get_profile(profile);
aa_put_profile(cxt->onexec);
cxt->onexec = profile;
commit_creds(new);
return 0;
}
/**
* aa_set_current_hat - set the current tasks hat
* @profile: profile to set as the current hat (NOT NULL)
* @token: token value that must be specified to change from the hat
*
* Do switch of tasks hat. If the task is currently in a hat
* validate the token to match.
*
* Returns: 0 or error on failure
*/
int aa_set_current_hat(struct aa_profile *profile, u64 token)
{
struct aa_task_cxt *cxt;
struct cred *new = prepare_creds();
if (!new)
return -ENOMEM;
BUG_ON(!profile);
cxt = cred_cxt(new);
if (!cxt->previous) {
/* transfer refcount */
cxt->previous = cxt->profile;
cxt->token = token;
} else if (cxt->token == token) {
aa_put_profile(cxt->profile);
} else {
/* previous_profile && cxt->token != token */
abort_creds(new);
return -EACCES;
}
cxt->profile = aa_get_newest_profile(profile);
/* clear exec on switching context */
aa_put_profile(cxt->onexec);
cxt->onexec = NULL;
commit_creds(new);
return 0;
}
/**
* aa_restore_previous_profile - exit from hat context restoring the profile
* @token: the token that must be matched to exit hat context
*
* Attempt to return out of a hat to the previous profile. The token
* must match the stored token value.
*
* Returns: 0 or error of failure
*/
int aa_restore_previous_profile(u64 token)
{
struct aa_task_cxt *cxt;
struct cred *new = prepare_creds();
if (!new)
return -ENOMEM;
cxt = cred_cxt(new);
if (cxt->token != token) {
abort_creds(new);
return -EACCES;
}
/* ignore restores when there is no saved profile */
if (!cxt->previous) {
abort_creds(new);
return 0;
}
aa_put_profile(cxt->profile);
cxt->profile = aa_get_newest_profile(cxt->previous);
BUG_ON(!cxt->profile);
/* clear exec && prev information when restoring to previous context */
aa_clear_task_cxt_trans(cxt);
commit_creds(new);
return 0;
}