android_kernel_xiaomi_sm8350/kernel/cred.c
David Howells de09a9771a CRED: Fix get_task_cred() and task_state() to not resurrect dead credentials
It's possible for get_task_cred() as it currently stands to 'corrupt' a set of
credentials by incrementing their usage count after their replacement by the
task being accessed.

What happens is that get_task_cred() can race with commit_creds():

	TASK_1			TASK_2			RCU_CLEANER
	-->get_task_cred(TASK_2)
	rcu_read_lock()
	__cred = __task_cred(TASK_2)
				-->commit_creds()
				old_cred = TASK_2->real_cred
				TASK_2->real_cred = ...
				put_cred(old_cred)
				  call_rcu(old_cred)
		[__cred->usage == 0]
	get_cred(__cred)
		[__cred->usage == 1]
	rcu_read_unlock()
							-->put_cred_rcu()
							[__cred->usage == 1]
							panic()

However, since a tasks credentials are generally not changed very often, we can
reasonably make use of a loop involving reading the creds pointer and using
atomic_inc_not_zero() to attempt to increment it if it hasn't already hit zero.

If successful, we can safely return the credentials in the knowledge that, even
if the task we're accessing has released them, they haven't gone to the RCU
cleanup code.

We then change task_state() in procfs to use get_task_cred() rather than
calling get_cred() on the result of __task_cred(), as that suffers from the
same problem.

Without this change, a BUG_ON in __put_cred() or in put_cred_rcu() can be
tripped when it is noticed that the usage count is not zero as it ought to be,
for example:

kernel BUG at kernel/cred.c:168!
invalid opcode: 0000 [#1] SMP
last sysfs file: /sys/kernel/mm/ksm/run
CPU 0
Pid: 2436, comm: master Not tainted 2.6.33.3-85.fc13.x86_64 #1 0HR330/OptiPlex
745
RIP: 0010:[<ffffffff81069881>]  [<ffffffff81069881>] __put_cred+0xc/0x45
RSP: 0018:ffff88019e7e9eb8  EFLAGS: 00010202
RAX: 0000000000000001 RBX: ffff880161514480 RCX: 00000000ffffffff
RDX: 00000000ffffffff RSI: ffff880140c690c0 RDI: ffff880140c690c0
RBP: ffff88019e7e9eb8 R08: 00000000000000d0 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000040 R12: ffff880140c690c0
R13: ffff88019e77aea0 R14: 00007fff336b0a5c R15: 0000000000000001
FS:  00007f12f50d97c0(0000) GS:ffff880007400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8f461bc000 CR3: 00000001b26ce000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process master (pid: 2436, threadinfo ffff88019e7e8000, task ffff88019e77aea0)
Stack:
 ffff88019e7e9ec8 ffffffff810698cd ffff88019e7e9ef8 ffffffff81069b45
<0> ffff880161514180 ffff880161514480 ffff880161514180 0000000000000000
<0> ffff88019e7e9f28 ffffffff8106aace 0000000000000001 0000000000000246
Call Trace:
 [<ffffffff810698cd>] put_cred+0x13/0x15
 [<ffffffff81069b45>] commit_creds+0x16b/0x175
 [<ffffffff8106aace>] set_current_groups+0x47/0x4e
 [<ffffffff8106ac89>] sys_setgroups+0xf6/0x105
 [<ffffffff81009b02>] system_call_fastpath+0x16/0x1b
Code: 48 8d 71 ff e8 7e 4e 15 00 85 c0 78 0b 8b 75 ec 48 89 df e8 ef 4a 15 00
48 83 c4 18 5b c9 c3 55 8b 07 8b 07 48 89 e5 85 c0 74 04 <0f> 0b eb fe 65 48 8b
04 25 00 cc 00 00 48 3b b8 58 04 00 00 75
RIP  [<ffffffff81069881>] __put_cred+0xc/0x45
 RSP <ffff88019e7e9eb8>
---[ end trace df391256a100ebdd ]---

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-07-29 15:16:17 -07:00

858 lines
22 KiB
C

/* Task credentials management - see Documentation/credentials.txt
*
* Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/module.h>
#include <linux/cred.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/key.h>
#include <linux/keyctl.h>
#include <linux/init_task.h>
#include <linux/security.h>
#include <linux/cn_proc.h>
#if 0
#define kdebug(FMT, ...) \
printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
#else
static inline __attribute__((format(printf, 1, 2)))
void no_printk(const char *fmt, ...)
{
}
#define kdebug(FMT, ...) \
no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
#endif
static struct kmem_cache *cred_jar;
/*
* The common credentials for the initial task's thread group
*/
#ifdef CONFIG_KEYS
static struct thread_group_cred init_tgcred = {
.usage = ATOMIC_INIT(2),
.tgid = 0,
.lock = SPIN_LOCK_UNLOCKED,
};
#endif
/*
* The initial credentials for the initial task
*/
struct cred init_cred = {
.usage = ATOMIC_INIT(4),
#ifdef CONFIG_DEBUG_CREDENTIALS
.subscribers = ATOMIC_INIT(2),
.magic = CRED_MAGIC,
#endif
.securebits = SECUREBITS_DEFAULT,
.cap_inheritable = CAP_INIT_INH_SET,
.cap_permitted = CAP_FULL_SET,
.cap_effective = CAP_INIT_EFF_SET,
.cap_bset = CAP_INIT_BSET,
.user = INIT_USER,
.group_info = &init_groups,
#ifdef CONFIG_KEYS
.tgcred = &init_tgcred,
#endif
};
static inline void set_cred_subscribers(struct cred *cred, int n)
{
#ifdef CONFIG_DEBUG_CREDENTIALS
atomic_set(&cred->subscribers, n);
#endif
}
static inline int read_cred_subscribers(const struct cred *cred)
{
#ifdef CONFIG_DEBUG_CREDENTIALS
return atomic_read(&cred->subscribers);
#else
return 0;
#endif
}
static inline void alter_cred_subscribers(const struct cred *_cred, int n)
{
#ifdef CONFIG_DEBUG_CREDENTIALS
struct cred *cred = (struct cred *) _cred;
atomic_add(n, &cred->subscribers);
#endif
}
/*
* Dispose of the shared task group credentials
*/
#ifdef CONFIG_KEYS
static void release_tgcred_rcu(struct rcu_head *rcu)
{
struct thread_group_cred *tgcred =
container_of(rcu, struct thread_group_cred, rcu);
BUG_ON(atomic_read(&tgcred->usage) != 0);
key_put(tgcred->session_keyring);
key_put(tgcred->process_keyring);
kfree(tgcred);
}
#endif
/*
* Release a set of thread group credentials.
*/
static void release_tgcred(struct cred *cred)
{
#ifdef CONFIG_KEYS
struct thread_group_cred *tgcred = cred->tgcred;
if (atomic_dec_and_test(&tgcred->usage))
call_rcu(&tgcred->rcu, release_tgcred_rcu);
#endif
}
/*
* The RCU callback to actually dispose of a set of credentials
*/
static void put_cred_rcu(struct rcu_head *rcu)
{
struct cred *cred = container_of(rcu, struct cred, rcu);
kdebug("put_cred_rcu(%p)", cred);
#ifdef CONFIG_DEBUG_CREDENTIALS
if (cred->magic != CRED_MAGIC_DEAD ||
atomic_read(&cred->usage) != 0 ||
read_cred_subscribers(cred) != 0)
panic("CRED: put_cred_rcu() sees %p with"
" mag %x, put %p, usage %d, subscr %d\n",
cred, cred->magic, cred->put_addr,
atomic_read(&cred->usage),
read_cred_subscribers(cred));
#else
if (atomic_read(&cred->usage) != 0)
panic("CRED: put_cred_rcu() sees %p with usage %d\n",
cred, atomic_read(&cred->usage));
#endif
security_cred_free(cred);
key_put(cred->thread_keyring);
key_put(cred->request_key_auth);
release_tgcred(cred);
if (cred->group_info)
put_group_info(cred->group_info);
free_uid(cred->user);
kmem_cache_free(cred_jar, cred);
}
/**
* __put_cred - Destroy a set of credentials
* @cred: The record to release
*
* Destroy a set of credentials on which no references remain.
*/
void __put_cred(struct cred *cred)
{
kdebug("__put_cred(%p{%d,%d})", cred,
atomic_read(&cred->usage),
read_cred_subscribers(cred));
BUG_ON(atomic_read(&cred->usage) != 0);
#ifdef CONFIG_DEBUG_CREDENTIALS
BUG_ON(read_cred_subscribers(cred) != 0);
cred->magic = CRED_MAGIC_DEAD;
cred->put_addr = __builtin_return_address(0);
#endif
BUG_ON(cred == current->cred);
BUG_ON(cred == current->real_cred);
call_rcu(&cred->rcu, put_cred_rcu);
}
EXPORT_SYMBOL(__put_cred);
/*
* Clean up a task's credentials when it exits
*/
void exit_creds(struct task_struct *tsk)
{
struct cred *cred;
kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
atomic_read(&tsk->cred->usage),
read_cred_subscribers(tsk->cred));
cred = (struct cred *) tsk->real_cred;
tsk->real_cred = NULL;
validate_creds(cred);
alter_cred_subscribers(cred, -1);
put_cred(cred);
cred = (struct cred *) tsk->cred;
tsk->cred = NULL;
validate_creds(cred);
alter_cred_subscribers(cred, -1);
put_cred(cred);
cred = (struct cred *) tsk->replacement_session_keyring;
if (cred) {
tsk->replacement_session_keyring = NULL;
validate_creds(cred);
put_cred(cred);
}
}
/**
* get_task_cred - Get another task's objective credentials
* @task: The task to query
*
* Get the objective credentials of a task, pinning them so that they can't go
* away. Accessing a task's credentials directly is not permitted.
*
* The caller must also make sure task doesn't get deleted, either by holding a
* ref on task or by holding tasklist_lock to prevent it from being unlinked.
*/
const struct cred *get_task_cred(struct task_struct *task)
{
const struct cred *cred;
rcu_read_lock();
do {
cred = __task_cred((task));
BUG_ON(!cred);
} while (!atomic_inc_not_zero(&((struct cred *)cred)->usage));
rcu_read_unlock();
return cred;
}
/*
* Allocate blank credentials, such that the credentials can be filled in at a
* later date without risk of ENOMEM.
*/
struct cred *cred_alloc_blank(void)
{
struct cred *new;
new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
if (!new)
return NULL;
#ifdef CONFIG_KEYS
new->tgcred = kzalloc(sizeof(*new->tgcred), GFP_KERNEL);
if (!new->tgcred) {
kmem_cache_free(cred_jar, new);
return NULL;
}
atomic_set(&new->tgcred->usage, 1);
#endif
atomic_set(&new->usage, 1);
if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
goto error;
#ifdef CONFIG_DEBUG_CREDENTIALS
new->magic = CRED_MAGIC;
#endif
return new;
error:
abort_creds(new);
return NULL;
}
/**
* prepare_creds - Prepare a new set of credentials for modification
*
* Prepare a new set of task credentials for modification. A task's creds
* shouldn't generally be modified directly, therefore this function is used to
* prepare a new copy, which the caller then modifies and then commits by
* calling commit_creds().
*
* Preparation involves making a copy of the objective creds for modification.
*
* Returns a pointer to the new creds-to-be if successful, NULL otherwise.
*
* Call commit_creds() or abort_creds() to clean up.
*/
struct cred *prepare_creds(void)
{
struct task_struct *task = current;
const struct cred *old;
struct cred *new;
validate_process_creds();
new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
if (!new)
return NULL;
kdebug("prepare_creds() alloc %p", new);
old = task->cred;
memcpy(new, old, sizeof(struct cred));
atomic_set(&new->usage, 1);
set_cred_subscribers(new, 0);
get_group_info(new->group_info);
get_uid(new->user);
#ifdef CONFIG_KEYS
key_get(new->thread_keyring);
key_get(new->request_key_auth);
atomic_inc(&new->tgcred->usage);
#endif
#ifdef CONFIG_SECURITY
new->security = NULL;
#endif
if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
goto error;
validate_creds(new);
return new;
error:
abort_creds(new);
return NULL;
}
EXPORT_SYMBOL(prepare_creds);
/*
* Prepare credentials for current to perform an execve()
* - The caller must hold current->cred_guard_mutex
*/
struct cred *prepare_exec_creds(void)
{
struct thread_group_cred *tgcred = NULL;
struct cred *new;
#ifdef CONFIG_KEYS
tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
if (!tgcred)
return NULL;
#endif
new = prepare_creds();
if (!new) {
kfree(tgcred);
return new;
}
#ifdef CONFIG_KEYS
/* newly exec'd tasks don't get a thread keyring */
key_put(new->thread_keyring);
new->thread_keyring = NULL;
/* create a new per-thread-group creds for all this set of threads to
* share */
memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred));
atomic_set(&tgcred->usage, 1);
spin_lock_init(&tgcred->lock);
/* inherit the session keyring; new process keyring */
key_get(tgcred->session_keyring);
tgcred->process_keyring = NULL;
release_tgcred(new);
new->tgcred = tgcred;
#endif
return new;
}
/*
* Copy credentials for the new process created by fork()
*
* We share if we can, but under some circumstances we have to generate a new
* set.
*
* The new process gets the current process's subjective credentials as its
* objective and subjective credentials
*/
int copy_creds(struct task_struct *p, unsigned long clone_flags)
{
#ifdef CONFIG_KEYS
struct thread_group_cred *tgcred;
#endif
struct cred *new;
int ret;
mutex_init(&p->cred_guard_mutex);
if (
#ifdef CONFIG_KEYS
!p->cred->thread_keyring &&
#endif
clone_flags & CLONE_THREAD
) {
p->real_cred = get_cred(p->cred);
get_cred(p->cred);
alter_cred_subscribers(p->cred, 2);
kdebug("share_creds(%p{%d,%d})",
p->cred, atomic_read(&p->cred->usage),
read_cred_subscribers(p->cred));
atomic_inc(&p->cred->user->processes);
return 0;
}
new = prepare_creds();
if (!new)
return -ENOMEM;
if (clone_flags & CLONE_NEWUSER) {
ret = create_user_ns(new);
if (ret < 0)
goto error_put;
}
#ifdef CONFIG_KEYS
/* new threads get their own thread keyrings if their parent already
* had one */
if (new->thread_keyring) {
key_put(new->thread_keyring);
new->thread_keyring = NULL;
if (clone_flags & CLONE_THREAD)
install_thread_keyring_to_cred(new);
}
/* we share the process and session keyrings between all the threads in
* a process - this is slightly icky as we violate COW credentials a
* bit */
if (!(clone_flags & CLONE_THREAD)) {
tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
if (!tgcred) {
ret = -ENOMEM;
goto error_put;
}
atomic_set(&tgcred->usage, 1);
spin_lock_init(&tgcred->lock);
tgcred->process_keyring = NULL;
tgcred->session_keyring = key_get(new->tgcred->session_keyring);
release_tgcred(new);
new->tgcred = tgcred;
}
#endif
atomic_inc(&new->user->processes);
p->cred = p->real_cred = get_cred(new);
alter_cred_subscribers(new, 2);
validate_creds(new);
return 0;
error_put:
put_cred(new);
return ret;
}
/**
* commit_creds - Install new credentials upon the current task
* @new: The credentials to be assigned
*
* Install a new set of credentials to the current task, using RCU to replace
* the old set. Both the objective and the subjective credentials pointers are
* updated. This function may not be called if the subjective credentials are
* in an overridden state.
*
* This function eats the caller's reference to the new credentials.
*
* Always returns 0 thus allowing this function to be tail-called at the end
* of, say, sys_setgid().
*/
int commit_creds(struct cred *new)
{
struct task_struct *task = current;
const struct cred *old = task->real_cred;
kdebug("commit_creds(%p{%d,%d})", new,
atomic_read(&new->usage),
read_cred_subscribers(new));
BUG_ON(task->cred != old);
#ifdef CONFIG_DEBUG_CREDENTIALS
BUG_ON(read_cred_subscribers(old) < 2);
validate_creds(old);
validate_creds(new);
#endif
BUG_ON(atomic_read(&new->usage) < 1);
get_cred(new); /* we will require a ref for the subj creds too */
/* dumpability changes */
if (old->euid != new->euid ||
old->egid != new->egid ||
old->fsuid != new->fsuid ||
old->fsgid != new->fsgid ||
!cap_issubset(new->cap_permitted, old->cap_permitted)) {
if (task->mm)
set_dumpable(task->mm, suid_dumpable);
task->pdeath_signal = 0;
smp_wmb();
}
/* alter the thread keyring */
if (new->fsuid != old->fsuid)
key_fsuid_changed(task);
if (new->fsgid != old->fsgid)
key_fsgid_changed(task);
/* do it
* - What if a process setreuid()'s and this brings the
* new uid over his NPROC rlimit? We can check this now
* cheaply with the new uid cache, so if it matters
* we should be checking for it. -DaveM
*/
alter_cred_subscribers(new, 2);
if (new->user != old->user)
atomic_inc(&new->user->processes);
rcu_assign_pointer(task->real_cred, new);
rcu_assign_pointer(task->cred, new);
if (new->user != old->user)
atomic_dec(&old->user->processes);
alter_cred_subscribers(old, -2);
/* send notifications */
if (new->uid != old->uid ||
new->euid != old->euid ||
new->suid != old->suid ||
new->fsuid != old->fsuid)
proc_id_connector(task, PROC_EVENT_UID);
if (new->gid != old->gid ||
new->egid != old->egid ||
new->sgid != old->sgid ||
new->fsgid != old->fsgid)
proc_id_connector(task, PROC_EVENT_GID);
/* release the old obj and subj refs both */
put_cred(old);
put_cred(old);
return 0;
}
EXPORT_SYMBOL(commit_creds);
/**
* abort_creds - Discard a set of credentials and unlock the current task
* @new: The credentials that were going to be applied
*
* Discard a set of credentials that were under construction and unlock the
* current task.
*/
void abort_creds(struct cred *new)
{
kdebug("abort_creds(%p{%d,%d})", new,
atomic_read(&new->usage),
read_cred_subscribers(new));
#ifdef CONFIG_DEBUG_CREDENTIALS
BUG_ON(read_cred_subscribers(new) != 0);
#endif
BUG_ON(atomic_read(&new->usage) < 1);
put_cred(new);
}
EXPORT_SYMBOL(abort_creds);
/**
* override_creds - Override the current process's subjective credentials
* @new: The credentials to be assigned
*
* Install a set of temporary override subjective credentials on the current
* process, returning the old set for later reversion.
*/
const struct cred *override_creds(const struct cred *new)
{
const struct cred *old = current->cred;
kdebug("override_creds(%p{%d,%d})", new,
atomic_read(&new->usage),
read_cred_subscribers(new));
validate_creds(old);
validate_creds(new);
get_cred(new);
alter_cred_subscribers(new, 1);
rcu_assign_pointer(current->cred, new);
alter_cred_subscribers(old, -1);
kdebug("override_creds() = %p{%d,%d}", old,
atomic_read(&old->usage),
read_cred_subscribers(old));
return old;
}
EXPORT_SYMBOL(override_creds);
/**
* revert_creds - Revert a temporary subjective credentials override
* @old: The credentials to be restored
*
* Revert a temporary set of override subjective credentials to an old set,
* discarding the override set.
*/
void revert_creds(const struct cred *old)
{
const struct cred *override = current->cred;
kdebug("revert_creds(%p{%d,%d})", old,
atomic_read(&old->usage),
read_cred_subscribers(old));
validate_creds(old);
validate_creds(override);
alter_cred_subscribers(old, 1);
rcu_assign_pointer(current->cred, old);
alter_cred_subscribers(override, -1);
put_cred(override);
}
EXPORT_SYMBOL(revert_creds);
/*
* initialise the credentials stuff
*/
void __init cred_init(void)
{
/* allocate a slab in which we can store credentials */
cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred),
0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
}
/**
* prepare_kernel_cred - Prepare a set of credentials for a kernel service
* @daemon: A userspace daemon to be used as a reference
*
* Prepare a set of credentials for a kernel service. This can then be used to
* override a task's own credentials so that work can be done on behalf of that
* task that requires a different subjective context.
*
* @daemon is used to provide a base for the security record, but can be NULL.
* If @daemon is supplied, then the security data will be derived from that;
* otherwise they'll be set to 0 and no groups, full capabilities and no keys.
*
* The caller may change these controls afterwards if desired.
*
* Returns the new credentials or NULL if out of memory.
*
* Does not take, and does not return holding current->cred_replace_mutex.
*/
struct cred *prepare_kernel_cred(struct task_struct *daemon)
{
const struct cred *old;
struct cred *new;
new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
if (!new)
return NULL;
kdebug("prepare_kernel_cred() alloc %p", new);
if (daemon)
old = get_task_cred(daemon);
else
old = get_cred(&init_cred);
validate_creds(old);
*new = *old;
get_uid(new->user);
get_group_info(new->group_info);
#ifdef CONFIG_KEYS
atomic_inc(&init_tgcred.usage);
new->tgcred = &init_tgcred;
new->request_key_auth = NULL;
new->thread_keyring = NULL;
new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
#endif
#ifdef CONFIG_SECURITY
new->security = NULL;
#endif
if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
goto error;
atomic_set(&new->usage, 1);
set_cred_subscribers(new, 0);
put_cred(old);
validate_creds(new);
return new;
error:
put_cred(new);
put_cred(old);
return NULL;
}
EXPORT_SYMBOL(prepare_kernel_cred);
/**
* set_security_override - Set the security ID in a set of credentials
* @new: The credentials to alter
* @secid: The LSM security ID to set
*
* Set the LSM security ID in a set of credentials so that the subjective
* security is overridden when an alternative set of credentials is used.
*/
int set_security_override(struct cred *new, u32 secid)
{
return security_kernel_act_as(new, secid);
}
EXPORT_SYMBOL(set_security_override);
/**
* set_security_override_from_ctx - Set the security ID in a set of credentials
* @new: The credentials to alter
* @secctx: The LSM security context to generate the security ID from.
*
* Set the LSM security ID in a set of credentials so that the subjective
* security is overridden when an alternative set of credentials is used. The
* security ID is specified in string form as a security context to be
* interpreted by the LSM.
*/
int set_security_override_from_ctx(struct cred *new, const char *secctx)
{
u32 secid;
int ret;
ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
if (ret < 0)
return ret;
return set_security_override(new, secid);
}
EXPORT_SYMBOL(set_security_override_from_ctx);
/**
* set_create_files_as - Set the LSM file create context in a set of credentials
* @new: The credentials to alter
* @inode: The inode to take the context from
*
* Change the LSM file creation context in a set of credentials to be the same
* as the object context of the specified inode, so that the new inodes have
* the same MAC context as that inode.
*/
int set_create_files_as(struct cred *new, struct inode *inode)
{
new->fsuid = inode->i_uid;
new->fsgid = inode->i_gid;
return security_kernel_create_files_as(new, inode);
}
EXPORT_SYMBOL(set_create_files_as);
#ifdef CONFIG_DEBUG_CREDENTIALS
bool creds_are_invalid(const struct cred *cred)
{
if (cred->magic != CRED_MAGIC)
return true;
#ifdef CONFIG_SECURITY_SELINUX
if (selinux_is_enabled()) {
if ((unsigned long) cred->security < PAGE_SIZE)
return true;
if ((*(u32 *)cred->security & 0xffffff00) ==
(POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
return true;
}
#endif
return false;
}
EXPORT_SYMBOL(creds_are_invalid);
/*
* dump invalid credentials
*/
static void dump_invalid_creds(const struct cred *cred, const char *label,
const struct task_struct *tsk)
{
printk(KERN_ERR "CRED: %s credentials: %p %s%s%s\n",
label, cred,
cred == &init_cred ? "[init]" : "",
cred == tsk->real_cred ? "[real]" : "",
cred == tsk->cred ? "[eff]" : "");
printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
cred->magic, cred->put_addr);
printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
atomic_read(&cred->usage),
read_cred_subscribers(cred));
printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
cred->uid, cred->euid, cred->suid, cred->fsuid);
printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
cred->gid, cred->egid, cred->sgid, cred->fsgid);
#ifdef CONFIG_SECURITY
printk(KERN_ERR "CRED: ->security is %p\n", cred->security);
if ((unsigned long) cred->security >= PAGE_SIZE &&
(((unsigned long) cred->security & 0xffffff00) !=
(POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
printk(KERN_ERR "CRED: ->security {%x, %x}\n",
((u32*)cred->security)[0],
((u32*)cred->security)[1]);
#endif
}
/*
* report use of invalid credentials
*/
void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
{
printk(KERN_ERR "CRED: Invalid credentials\n");
printk(KERN_ERR "CRED: At %s:%u\n", file, line);
dump_invalid_creds(cred, "Specified", current);
BUG();
}
EXPORT_SYMBOL(__invalid_creds);
/*
* check the credentials on a process
*/
void __validate_process_creds(struct task_struct *tsk,
const char *file, unsigned line)
{
if (tsk->cred == tsk->real_cred) {
if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
creds_are_invalid(tsk->cred)))
goto invalid_creds;
} else {
if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
read_cred_subscribers(tsk->cred) < 1 ||
creds_are_invalid(tsk->real_cred) ||
creds_are_invalid(tsk->cred)))
goto invalid_creds;
}
return;
invalid_creds:
printk(KERN_ERR "CRED: Invalid process credentials\n");
printk(KERN_ERR "CRED: At %s:%u\n", file, line);
dump_invalid_creds(tsk->real_cred, "Real", tsk);
if (tsk->cred != tsk->real_cred)
dump_invalid_creds(tsk->cred, "Effective", tsk);
else
printk(KERN_ERR "CRED: Effective creds == Real creds\n");
BUG();
}
EXPORT_SYMBOL(__validate_process_creds);
/*
* check creds for do_exit()
*/
void validate_creds_for_do_exit(struct task_struct *tsk)
{
kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
tsk->real_cred, tsk->cred,
atomic_read(&tsk->cred->usage),
read_cred_subscribers(tsk->cred));
__validate_process_creds(tsk, __FILE__, __LINE__);
}
#endif /* CONFIG_DEBUG_CREDENTIALS */