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kernel_xiaomi_raphael/include/linux/init_task.h
Elena Reshetova 1a477a2949 sched/core: Convert task_struct.usage to refcount_t 
atomic_t variables are currently used to implement reference
counters with the following properties:

 - counter is initialized to 1 using atomic_set()
 - a resource is freed upon counter reaching zero
 - once counter reaches zero, its further
   increments aren't allowed
 - counter schema uses basic atomic operations
   (set, inc, inc_not_zero, dec_and_test, etc.)

Such atomic variables should be converted to a newly provided
refcount_t type and API that prevents accidental counter overflows
and underflows. This is important since overflows and underflows
can lead to use-after-free situation and be exploitable.

The variable task_struct.usage is used as pure reference counter.
Convert it to refcount_t and fix up the operations.

** Important note for maintainers:

Some functions from refcount_t API defined in lib/refcount.c
have different memory ordering guarantees than their atomic
counterparts.

The full comparison can be seen in
https://lkml.org/lkml/2017/11/15/57 and it is hopefully soon
in state to be merged to the documentation tree.

Normally the differences should not matter since refcount_t provides
enough guarantees to satisfy the refcounting use cases, but in
some rare cases it might matter.

Please double check that you don't have some undocumented
memory guarantees for this variable usage.

For the task_struct.usage it might make a difference
in following places:

 - put_task_struct(): decrement in refcount_dec_and_test() only
   provides RELEASE ordering and control dependency on success
   vs. fully ordered atomic counterpart

Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Reviewed-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akpm@linux-foundation.org
Cc: viro@zeniv.linux.org.uk
Link: https://lkml.kernel.org/r/1547814450-18902-5-git-send-email-elena.reshetova@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Alexander Winkowski <dereference23@outlook.com>
2023-02-14 12:57:06 +02:00

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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX__INIT_TASK_H
#define _LINUX__INIT_TASK_H
#include <linux/rcupdate.h>
#include <linux/irqflags.h>
#include <linux/utsname.h>
#include <linux/lockdep.h>
#include <linux/ftrace.h>
#include <linux/ipc.h>
#include <linux/pid_namespace.h>
#include <linux/user_namespace.h>
#include <linux/securebits.h>
#include <linux/seqlock.h>
#include <linux/rbtree.h>
#include <linux/sched/autogroup.h>
#include <net/net_namespace.h>
#include <linux/sched/rt.h>
#include <linux/livepatch.h>
#include <linux/mm_types.h>
#include <asm/thread_info.h>
#ifdef CONFIG_SMP
# define INIT_PUSHABLE_TASKS(tsk) \
.pushable_tasks = PLIST_NODE_INIT(tsk.pushable_tasks, MAX_PRIO),
#else
# define INIT_PUSHABLE_TASKS(tsk)
#endif
extern struct files_struct init_files;
extern struct fs_struct init_fs;
#ifdef CONFIG_CPUSETS
#define INIT_CPUSET_SEQ(tsk) \
.mems_allowed_seq = SEQCNT_ZERO(tsk.mems_allowed_seq),
#else
#define INIT_CPUSET_SEQ(tsk)
#endif
#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
#define INIT_PREV_CPUTIME(x) .prev_cputime = { \
.lock = __RAW_SPIN_LOCK_UNLOCKED(x.prev_cputime.lock), \
},
#else
#define INIT_PREV_CPUTIME(x)
#endif
#ifdef CONFIG_POSIX_TIMERS
#define INIT_POSIX_TIMERS(s) \
.posix_timers = LIST_HEAD_INIT(s.posix_timers),
#define INIT_CPU_TIMERS(s) \
.cpu_timers = { \
LIST_HEAD_INIT(s.cpu_timers[0]), \
LIST_HEAD_INIT(s.cpu_timers[1]), \
LIST_HEAD_INIT(s.cpu_timers[2]), \
},
#define INIT_CPUTIMER(s) \
.cputimer = { \
.cputime_atomic = INIT_CPUTIME_ATOMIC, \
.running = false, \
.checking_timer = false, \
},
#else
#define INIT_POSIX_TIMERS(s)
#define INIT_CPU_TIMERS(s)
#define INIT_CPUTIMER(s)
#endif
#define INIT_SIGNALS(sig) { \
.nr_threads = 1, \
.thread_head = LIST_HEAD_INIT(init_task.thread_node), \
.wait_chldexit = __WAIT_QUEUE_HEAD_INITIALIZER(sig.wait_chldexit),\
.shared_pending = { \
.list = LIST_HEAD_INIT(sig.shared_pending.list), \
.signal = {{0}}}, \
INIT_POSIX_TIMERS(sig) \
INIT_CPU_TIMERS(sig) \
.rlim = INIT_RLIMITS, \
INIT_CPUTIMER(sig) \
INIT_PREV_CPUTIME(sig) \
.cred_guard_mutex = \
__MUTEX_INITIALIZER(sig.cred_guard_mutex), \
}
extern struct nsproxy init_nsproxy;
#define INIT_SIGHAND(sighand) { \
.count = ATOMIC_INIT(1), \
.action = { { { .sa_handler = SIG_DFL, } }, }, \
.siglock = __SPIN_LOCK_UNLOCKED(sighand.siglock), \
.signalfd_wqh = __WAIT_QUEUE_HEAD_INITIALIZER(sighand.signalfd_wqh), \
}
extern struct group_info init_groups;
#define INIT_STRUCT_PID { \
.count = ATOMIC_INIT(1), \
.tasks = { \
{ .first = NULL }, \
{ .first = NULL }, \
{ .first = NULL }, \
}, \
.level = 0, \
.numbers = { { \
.nr = 0, \
.ns = &init_pid_ns, \
.pid_chain = { .next = NULL, .pprev = NULL }, \
}, } \
}
#define INIT_PID_LINK(type) \
{ \
.node = { \
.next = NULL, \
.pprev = NULL, \
}, \
.pid = &init_struct_pid, \
}
#ifdef CONFIG_AUDITSYSCALL
#define INIT_IDS \
.loginuid = INVALID_UID, \
.sessionid = (unsigned int)-1,
#else
#define INIT_IDS
#endif
#ifdef CONFIG_PREEMPT_RCU
#define INIT_TASK_RCU_PREEMPT(tsk) \
.rcu_read_lock_nesting = 0, \
.rcu_read_unlock_special.s = 0, \
.rcu_node_entry = LIST_HEAD_INIT(tsk.rcu_node_entry), \
.rcu_blocked_node = NULL,
#else
#define INIT_TASK_RCU_PREEMPT(tsk)
#endif
#ifdef CONFIG_TASKS_RCU
#define INIT_TASK_RCU_TASKS(tsk) \
.rcu_tasks_holdout = false, \
.rcu_tasks_holdout_list = \
LIST_HEAD_INIT(tsk.rcu_tasks_holdout_list), \
.rcu_tasks_idle_cpu = -1,
#else
#define INIT_TASK_RCU_TASKS(tsk)
#endif
extern struct cred init_cred;
#ifdef CONFIG_CGROUP_SCHED
# define INIT_CGROUP_SCHED(tsk) \
.sched_task_group = &root_task_group,
#else
# define INIT_CGROUP_SCHED(tsk)
#endif
#ifdef CONFIG_PERF_EVENTS
# define INIT_PERF_EVENTS(tsk) \
.perf_event_mutex = \
__MUTEX_INITIALIZER(tsk.perf_event_mutex), \
.perf_event_list = LIST_HEAD_INIT(tsk.perf_event_list),
#else
# define INIT_PERF_EVENTS(tsk)
#endif
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
# define INIT_VTIME(tsk) \
.vtime.seqcount = SEQCNT_ZERO(tsk.vtime.seqcount), \
.vtime.starttime = 0, \
.vtime.state = VTIME_SYS,
#else
# define INIT_VTIME(tsk)
#endif
#define INIT_TASK_COMM "swapper"
#ifdef CONFIG_RT_MUTEXES
# define INIT_RT_MUTEXES(tsk) \
.pi_waiters = RB_ROOT_CACHED, \
.pi_top_task = NULL,
#else
# define INIT_RT_MUTEXES(tsk)
#endif
#ifdef CONFIG_NUMA_BALANCING
# define INIT_NUMA_BALANCING(tsk) \
.numa_preferred_nid = -1, \
.numa_group = NULL, \
.numa_faults = NULL,
#else
# define INIT_NUMA_BALANCING(tsk)
#endif
#ifdef CONFIG_KASAN
# define INIT_KASAN(tsk) \
.kasan_depth = 1,
#else
# define INIT_KASAN(tsk)
#endif
#ifdef CONFIG_LIVEPATCH
# define INIT_LIVEPATCH(tsk) \
.patch_state = KLP_UNDEFINED,
#else
# define INIT_LIVEPATCH(tsk)
#endif
#ifdef CONFIG_THREAD_INFO_IN_TASK
# define INIT_TASK_TI(tsk) \
.thread_info = INIT_THREAD_INFO(tsk), \
.stack_refcount = ATOMIC_INIT(1),
#else
# define INIT_TASK_TI(tsk)
#endif
#ifdef CONFIG_SECURITY
#define INIT_TASK_SECURITY .security = NULL,
#else
#define INIT_TASK_SECURITY
#endif
/*
* INIT_TASK is used to set up the first task table, touch at
* your own risk!. Base=0, limit=0x1fffff (=2MB)
*/
#define INIT_TASK(tsk) \
{ \
INIT_TASK_TI(tsk) \
.state = 0, \
.stack = init_stack, \
.usage = REFCOUNT_INIT(2), \
.flags = PF_KTHREAD, \
.prio = MAX_PRIO-20, \
.static_prio = MAX_PRIO-20, \
.normal_prio = MAX_PRIO-20, \
.policy = SCHED_NORMAL, \
.cpus_ptr = &tsk.cpus_mask, \
.cpus_mask = CPU_MASK_ALL, \
.nr_cpus_allowed= NR_CPUS, \
.cpus_requested = CPU_MASK_ALL, \
.mm = NULL, \
.active_mm = &init_mm, \
.restart_block = { \
.fn = do_no_restart_syscall, \
}, \
.se = { \
.group_node = LIST_HEAD_INIT(tsk.se.group_node), \
}, \
.rt = { \
.run_list = LIST_HEAD_INIT(tsk.rt.run_list), \
.time_slice = RR_TIMESLICE, \
}, \
.tasks = LIST_HEAD_INIT(tsk.tasks), \
INIT_PUSHABLE_TASKS(tsk) \
INIT_CGROUP_SCHED(tsk) \
.ptraced = LIST_HEAD_INIT(tsk.ptraced), \
.ptrace_entry = LIST_HEAD_INIT(tsk.ptrace_entry), \
.real_parent = &tsk, \
.parent = &tsk, \
.children = LIST_HEAD_INIT(tsk.children), \
.sibling = LIST_HEAD_INIT(tsk.sibling), \
.group_leader = &tsk, \
RCU_POINTER_INITIALIZER(real_cred, &init_cred), \
RCU_POINTER_INITIALIZER(cred, &init_cred), \
.comm = INIT_TASK_COMM, \
.thread = INIT_THREAD, \
.fs = &init_fs, \
.files = &init_files, \
.signal = &init_signals, \
.sighand = &init_sighand, \
.nsproxy = &init_nsproxy, \
.pending = { \
.list = LIST_HEAD_INIT(tsk.pending.list), \
.signal = {{0}}}, \
.blocked = {{0}}, \
.alloc_lock = __SPIN_LOCK_UNLOCKED(tsk.alloc_lock), \
.journal_info = NULL, \
INIT_CPU_TIMERS(tsk) \
.pi_lock = __RAW_SPIN_LOCK_UNLOCKED(tsk.pi_lock), \
.timer_slack_ns = 50000, /* 50 usec default slack */ \
.pids = { \
[PIDTYPE_PID] = INIT_PID_LINK(PIDTYPE_PID), \
[PIDTYPE_PGID] = INIT_PID_LINK(PIDTYPE_PGID), \
[PIDTYPE_SID] = INIT_PID_LINK(PIDTYPE_SID), \
}, \
.thread_group = LIST_HEAD_INIT(tsk.thread_group), \
.thread_node = LIST_HEAD_INIT(init_signals.thread_head), \
INIT_IDS \
INIT_PERF_EVENTS(tsk) \
INIT_TRACE_IRQFLAGS \
INIT_LOCKDEP \
INIT_FTRACE_GRAPH \
INIT_TRACE_RECURSION \
INIT_TASK_RCU_PREEMPT(tsk) \
INIT_TASK_RCU_TASKS(tsk) \
INIT_CPUSET_SEQ(tsk) \
INIT_RT_MUTEXES(tsk) \
INIT_PREV_CPUTIME(tsk) \
INIT_VTIME(tsk) \
INIT_NUMA_BALANCING(tsk) \
INIT_KASAN(tsk) \
INIT_LIVEPATCH(tsk) \
INIT_TASK_SECURITY \
}
/* Attach to the init_task data structure for proper alignment */
#define __init_task_data __attribute__((__section__(".data..init_task")))
#endif
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