1
// SPDX-License-Identifier: GPL-2.0
2
/*
3
 *  linux/kernel/acct.c
4
 *
5
 *  BSD Process Accounting for Linux
6
 *
7
 *  Author: Marco van Wieringen <[email protected]>
8
 *
9
 *  Some code based on ideas and code from:
10
 *  Thomas K. Dyas <[email protected]>
11
 *
12
 *  This file implements BSD-style process accounting. Whenever any
13
 *  process exits, an accounting record of type "struct acct" is
14
 *  written to the file specified with the acct() system call. It is
15
 *  up to user-level programs to do useful things with the accounting
16
 *  log. The kernel just provides the raw accounting information.
17
 *
18
 * (C) Copyright 1995 - 1997 Marco van Wieringen - ELM Consultancy B.V.
19
 *
20
 *  Plugged two leaks. 1) It didn't return acct_file into the free_filps if
21
 *  the file happened to be read-only. 2) If the accounting was suspended
22
 *  due to the lack of space it happily allowed to reopen it and completely
23
 *  lost the old acct_file. 3/10/98, Al Viro.
24
 *
25
 *  Now we silently close acct_file on attempt to reopen. Cleaned sys_acct().
26
 *  XTerms and EMACS are manifestations of pure evil. 21/10/98, AV.
27
 *
28
 *  Fixed a nasty interaction with sys_umount(). If the accounting
29
 *  was suspeneded we failed to stop it on umount(). Messy.
30
 *  Another one: remount to readonly didn't stop accounting.
31
 *	Question: what should we do if we have CAP_SYS_ADMIN but not
32
 *  CAP_SYS_PACCT? Current code does the following: umount returns -EBUSY
33
 *  unless we are messing with the root. In that case we are getting a
34
 *  real mess with do_remount_sb(). 9/11/98, AV.
35
 *
36
 *  Fixed a bunch of races (and pair of leaks). Probably not the best way,
37
 *  but this one obviously doesn't introduce deadlocks. Later. BTW, found
38
 *  one race (and leak) in BSD implementation.
39
 *  OK, that's better. ANOTHER race and leak in BSD variant. There always
40
 *  is one more bug... 10/11/98, AV.
41
 *
42
 *	Oh, fsck... Oopsable SMP race in do_process_acct() - we must hold
43
 * ->mmap_lock to walk the vma list of current->mm. Nasty, since it leaks
44
 * a struct file opened for write. Fixed. 2/6/2000, AV.
45
 */
46

47
#include <linux/slab.h>
48
#include <linux/acct.h>
49
#include <linux/capability.h>
50
#include <linux/tty.h>
51
#include <linux/statfs.h>
52
#include <linux/jiffies.h>
53
#include <linux/syscalls.h>
54
#include <linux/namei.h>
55
#include <linux/sched/cputime.h>
56

57
#include <asm/div64.h>
58
#include <linux/pid_namespace.h>
59
#include <linux/fs_pin.h>
60

61
/*
62
 * These constants control the amount of freespace that suspend and
63
 * resume the process accounting system, and the time delay between
64
 * each check.
65
 * Turned into sysctl-controllable parameters. AV, 12/11/98
66
 */
67

68
static int acct_parm[3] = {4, 2, 30};
69
#define RESUME		(acct_parm[0])	/* >foo% free space - resume */
70
#define SUSPEND		(acct_parm[1])	/* <foo% free space - suspend */
71
#define ACCT_TIMEOUT	(acct_parm[2])	/* foo second timeout between checks */
72

73
#ifdef CONFIG_SYSCTL
74
static const struct ctl_table kern_acct_table[] = {
75
	{
76
		.procname       = "acct",
77
		.data           = &acct_parm,
78
		.maxlen         = 3*sizeof(int),
79
		.mode           = 0644,
80
		.proc_handler   = proc_dointvec,
81
	},
82
};
83

84
static __init int kernel_acct_sysctls_init(void)
85
{
86
	register_sysctl_init("kernel", kern_acct_table);
87
	return 0;
88
}
89
late_initcall(kernel_acct_sysctls_init);
90
#endif /* CONFIG_SYSCTL */
91

92
/*
93
 * External references and all of the globals.
94
 */
95

96
struct bsd_acct_struct {
97
	struct fs_pin		pin;
98
	atomic_long_t		count;
99
	struct rcu_head		rcu;
100
	struct mutex		lock;
101
	bool			active;
102
	bool			check_space;
103
	unsigned long		needcheck;
104
	struct file		*file;
105
	struct pid_namespace	*ns;
106
	struct work_struct	work;
107
	struct completion	done;
108
	acct_t			ac;
109
};
110

111
static void fill_ac(struct bsd_acct_struct *acct);
112
static void acct_write_process(struct bsd_acct_struct *acct);
113

114
/*
115
 * Check the amount of free space and suspend/resume accordingly.
116
 */
117
static bool check_free_space(struct bsd_acct_struct *acct)
118
{
119
	struct kstatfs sbuf;
120

121
	if (!acct->check_space)
122
		return acct->active;
123

124
	/* May block */
125
	if (vfs_statfs(&acct->file->f_path, &sbuf))
126
		return acct->active;
127

128
	if (acct->active) {
129
		u64 suspend = sbuf.f_blocks * SUSPEND;
130
		do_div(suspend, 100);
131
		if (sbuf.f_bavail <= suspend) {
132
			acct->active = false;
133
			pr_info("Process accounting paused\n");
134
		}
135
	} else {
136
		u64 resume = sbuf.f_blocks * RESUME;
137
		do_div(resume, 100);
138
		if (sbuf.f_bavail >= resume) {
139
			acct->active = true;
140
			pr_info("Process accounting resumed\n");
141
		}
142
	}
143

144
	acct->needcheck = jiffies + ACCT_TIMEOUT*HZ;
145
	return acct->active;
146
}
147

148
static void acct_put(struct bsd_acct_struct *p)
149
{
150
	if (atomic_long_dec_and_test(&p->count))
151
		kfree_rcu(p, rcu);
152
}
153

154
static inline struct bsd_acct_struct *to_acct(struct fs_pin *p)
155
{
156
	return p ? container_of(p, struct bsd_acct_struct, pin) : NULL;
157
}
158

159
static struct bsd_acct_struct *acct_get(struct pid_namespace *ns)
160
{
161
	struct bsd_acct_struct *res;
162
again:
163
	smp_rmb();
164
	rcu_read_lock();
165
	res = to_acct(READ_ONCE(ns->bacct));
166
	if (!res) {
167
		rcu_read_unlock();
168
		return NULL;
169
	}
170
	if (!atomic_long_inc_not_zero(&res->count)) {
171
		rcu_read_unlock();
172
		cpu_relax();
173
		goto again;
174
	}
175
	rcu_read_unlock();
176
	mutex_lock(&res->lock);
177
	if (res != to_acct(READ_ONCE(ns->bacct))) {
178
		mutex_unlock(&res->lock);
179
		acct_put(res);
180
		goto again;
181
	}
182
	return res;
183
}
184

185
static void acct_pin_kill(struct fs_pin *pin)
186
{
187
	struct bsd_acct_struct *acct = to_acct(pin);
188
	mutex_lock(&acct->lock);
189
	/*
190
	 * Fill the accounting struct with the exiting task's info
191
	 * before punting to the workqueue.
192
	 */
193
	fill_ac(acct);
194
	schedule_work(&acct->work);
195
	wait_for_completion(&acct->done);
196
	cmpxchg(&acct->ns->bacct, pin, NULL);
197
	mutex_unlock(&acct->lock);
198
	pin_remove(pin);
199
	acct_put(acct);
200
}
201

202
static void close_work(struct work_struct *work)
203
{
204
	struct bsd_acct_struct *acct = container_of(work, struct bsd_acct_struct, work);
205
	struct file *file = acct->file;
206

207
	/* We were fired by acct_pin_kill() which holds acct->lock. */
208
	acct_write_process(acct);
209
	if (file->f_op->flush)
210
		file->f_op->flush(file, NULL);
211
	__fput_sync(file);
212
	complete(&acct->done);
213
}
214

215
DEFINE_FREE(fput_sync, struct file *, if (!IS_ERR_OR_NULL(_T)) __fput_sync(_T))
216
static int acct_on(const char __user *name)
217
{
218
	/* Difference from BSD - they don't do O_APPEND */
219
	const int open_flags = O_WRONLY|O_APPEND|O_LARGEFILE;
220
	struct pid_namespace *ns = task_active_pid_ns(current);
221
	struct filename *pathname __free(putname) = getname(name);
222
	struct file *original_file __free(fput) = NULL;	// in that order
223
	struct path internal __free(path_put) = {};	// in that order
224
	struct file *file __free(fput_sync) = NULL;	// in that order
225
	struct bsd_acct_struct *acct;
226
	struct vfsmount *mnt;
227
	struct fs_pin *old;
228

229
	if (IS_ERR(pathname))
230
		return PTR_ERR(pathname);
231
	original_file = file_open_name(pathname, open_flags, 0);
232
	if (IS_ERR(original_file))
233
		return PTR_ERR(original_file);
234

235
	mnt = mnt_clone_internal(&original_file->f_path);
236
	if (IS_ERR(mnt))
237
		return PTR_ERR(mnt);
238

239
	internal.mnt = mnt;
240
	internal.dentry = dget(mnt->mnt_root);
241

242
	file = dentry_open(&internal, open_flags, current_cred());
243
	if (IS_ERR(file))
244
		return PTR_ERR(file);
245

246
	if (!S_ISREG(file_inode(file)->i_mode))
247
		return -EACCES;
248

249
	/* Exclude kernel kernel internal filesystems. */
250
	if (file_inode(file)->i_sb->s_flags & (SB_NOUSER | SB_KERNMOUNT))
251
		return -EINVAL;
252

253
	/* Exclude procfs and sysfs. */
254
	if (file_inode(file)->i_sb->s_iflags & SB_I_USERNS_VISIBLE)
255
		return -EINVAL;
256

257
	if (!(file->f_mode & FMODE_CAN_WRITE))
258
		return -EIO;
259

260
	acct = kzalloc(sizeof(struct bsd_acct_struct), GFP_KERNEL);
261
	if (!acct)
262
		return -ENOMEM;
263

264
	atomic_long_set(&acct->count, 1);
265
	init_fs_pin(&acct->pin, acct_pin_kill);
266
	acct->file = no_free_ptr(file);
267
	acct->needcheck = jiffies;
268
	acct->ns = ns;
269
	mutex_init(&acct->lock);
270
	INIT_WORK(&acct->work, close_work);
271
	init_completion(&acct->done);
272
	mutex_lock_nested(&acct->lock, 1);	/* nobody has seen it yet */
273
	pin_insert(&acct->pin, original_file->f_path.mnt);
274

275
	rcu_read_lock();
276
	old = xchg(&ns->bacct, &acct->pin);
277
	mutex_unlock(&acct->lock);
278
	pin_kill(old);
279
	return 0;
280
}
281

282
static DEFINE_MUTEX(acct_on_mutex);
283

284
/**
285
 * sys_acct - enable/disable process accounting
286
 * @name: file name for accounting records or NULL to shutdown accounting
287
 *
288
 * sys_acct() is the only system call needed to implement process
289
 * accounting. It takes the name of the file where accounting records
290
 * should be written. If the filename is NULL, accounting will be
291
 * shutdown.
292
 *
293
 * Returns: 0 for success or negative errno values for failure.
294
 */
295
SYSCALL_DEFINE1(acct, const char __user *, name)
296
{
297
	int error = 0;
298

299
	if (!capable(CAP_SYS_PACCT))
300
		return -EPERM;
301

302
	if (name) {
303
		mutex_lock(&acct_on_mutex);
304
		error = acct_on(name);
305
		mutex_unlock(&acct_on_mutex);
306
	} else {
307
		rcu_read_lock();
308
		pin_kill(task_active_pid_ns(current)->bacct);
309
	}
310

311
	return error;
312
}
313

314
void acct_exit_ns(struct pid_namespace *ns)
315
{
316
	rcu_read_lock();
317
	pin_kill(ns->bacct);
318
}
319

320
/*
321
 *  encode an u64 into a comp_t
322
 *
323
 *  This routine has been adopted from the encode_comp_t() function in
324
 *  the kern_acct.c file of the FreeBSD operating system. The encoding
325
 *  is a 13-bit fraction with a 3-bit (base 8) exponent.
326
 */
327

328
#define	MANTSIZE	13			/* 13 bit mantissa. */
329
#define	EXPSIZE		3			/* Base 8 (3 bit) exponent. */
330
#define	MAXFRACT	((1 << MANTSIZE) - 1)	/* Maximum fractional value. */
331

332
static comp_t encode_comp_t(u64 value)
333
{
334
	int exp, rnd;
335

336
	exp = rnd = 0;
337
	while (value > MAXFRACT) {
338
		rnd = value & (1 << (EXPSIZE - 1));	/* Round up? */
339
		value >>= EXPSIZE;	/* Base 8 exponent == 3 bit shift. */
340
		exp++;
341
	}
342

343
	/*
344
	 * If we need to round up, do it (and handle overflow correctly).
345
	 */
346
	if (rnd && (++value > MAXFRACT)) {
347
		value >>= EXPSIZE;
348
		exp++;
349
	}
350

351
	if (exp > (((comp_t) ~0U) >> MANTSIZE))
352
		return (comp_t) ~0U;
353
	/*
354
	 * Clean it up and polish it off.
355
	 */
356
	exp <<= MANTSIZE;		/* Shift the exponent into place */
357
	exp += value;			/* and add on the mantissa. */
358
	return exp;
359
}
360

361
#if ACCT_VERSION == 1 || ACCT_VERSION == 2
362
/*
363
 * encode an u64 into a comp2_t (24 bits)
364
 *
365
 * Format: 5 bit base 2 exponent, 20 bits mantissa.
366
 * The leading bit of the mantissa is not stored, but implied for
367
 * non-zero exponents.
368
 * Largest encodable value is 50 bits.
369
 */
370

371
#define MANTSIZE2       20                      /* 20 bit mantissa. */
372
#define EXPSIZE2        5                       /* 5 bit base 2 exponent. */
373
#define MAXFRACT2       ((1ul << MANTSIZE2) - 1) /* Maximum fractional value. */
374
#define MAXEXP2         ((1 << EXPSIZE2) - 1)    /* Maximum exponent. */
375

376
static comp2_t encode_comp2_t(u64 value)
377
{
378
	int exp, rnd;
379

380
	exp = (value > (MAXFRACT2>>1));
381
	rnd = 0;
382
	while (value > MAXFRACT2) {
383
		rnd = value & 1;
384
		value >>= 1;
385
		exp++;
386
	}
387

388
	/*
389
	 * If we need to round up, do it (and handle overflow correctly).
390
	 */
391
	if (rnd && (++value > MAXFRACT2)) {
392
		value >>= 1;
393
		exp++;
394
	}
395

396
	if (exp > MAXEXP2) {
397
		/* Overflow. Return largest representable number instead. */
398
		return (1ul << (MANTSIZE2+EXPSIZE2-1)) - 1;
399
	} else {
400
		return (value & (MAXFRACT2>>1)) | (exp << (MANTSIZE2-1));
401
	}
402
}
403
#elif ACCT_VERSION == 3
404
/*
405
 * encode an u64 into a 32 bit IEEE float
406
 */
407
static u32 encode_float(u64 value)
408
{
409
	unsigned exp = 190;
410
	unsigned u;
411

412
	if (value == 0)
413
		return 0;
414
	while ((s64)value > 0) {
415
		value <<= 1;
416
		exp--;
417
	}
418
	u = (u32)(value >> 40) & 0x7fffffu;
419
	return u | (exp << 23);
420
}
421
#endif
422

423
/*
424
 *  Write an accounting entry for an exiting process
425
 *
426
 *  The acct_process() call is the workhorse of the process
427
 *  accounting system. The struct acct is built here and then written
428
 *  into the accounting file. This function should only be called from
429
 *  do_exit() or when switching to a different output file.
430
 */
431

432
static void fill_ac(struct bsd_acct_struct *acct)
433
{
434
	struct pacct_struct *pacct = &current->signal->pacct;
435
	struct file *file = acct->file;
436
	acct_t *ac = &acct->ac;
437
	u64 elapsed, run_time;
438
	time64_t btime;
439
	struct tty_struct *tty;
440

441
	lockdep_assert_held(&acct->lock);
442

443
	if (time_is_after_jiffies(acct->needcheck)) {
444
		acct->check_space = false;
445

446
		/* Don't fill in @ac if nothing will be written. */
447
		if (!acct->active)
448
			return;
449
	} else {
450
		acct->check_space = true;
451
	}
452

453
	/*
454
	 * Fill the accounting struct with the needed info as recorded
455
	 * by the different kernel functions.
456
	 */
457
	memset(ac, 0, sizeof(acct_t));
458

459
	ac->ac_version = ACCT_VERSION | ACCT_BYTEORDER;
460
	strscpy(ac->ac_comm, current->comm, sizeof(ac->ac_comm));
461

462
	/* calculate run_time in nsec*/
463
	run_time = ktime_get_ns();
464
	run_time -= current->group_leader->start_time;
465
	/* convert nsec -> AHZ */
466
	elapsed = nsec_to_AHZ(run_time);
467
#if ACCT_VERSION == 3
468
	ac->ac_etime = encode_float(elapsed);
469
#else
470
	ac->ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ?
471
				(unsigned long) elapsed : (unsigned long) -1l);
472
#endif
473
#if ACCT_VERSION == 1 || ACCT_VERSION == 2
474
	{
475
		/* new enlarged etime field */
476
		comp2_t etime = encode_comp2_t(elapsed);
477

478
		ac->ac_etime_hi = etime >> 16;
479
		ac->ac_etime_lo = (u16) etime;
480
	}
481
#endif
482
	do_div(elapsed, AHZ);
483
	btime = ktime_get_real_seconds() - elapsed;
484
	ac->ac_btime = clamp_t(time64_t, btime, 0, U32_MAX);
485
#if ACCT_VERSION == 2
486
	ac->ac_ahz = AHZ;
487
#endif
488

489
	spin_lock_irq(&current->sighand->siglock);
490
	tty = current->signal->tty;	/* Safe as we hold the siglock */
491
	ac->ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0;
492
	ac->ac_utime = encode_comp_t(nsec_to_AHZ(pacct->ac_utime));
493
	ac->ac_stime = encode_comp_t(nsec_to_AHZ(pacct->ac_stime));
494
	ac->ac_flag = pacct->ac_flag;
495
	ac->ac_mem = encode_comp_t(pacct->ac_mem);
496
	ac->ac_minflt = encode_comp_t(pacct->ac_minflt);
497
	ac->ac_majflt = encode_comp_t(pacct->ac_majflt);
498
	ac->ac_exitcode = pacct->ac_exitcode;
499
	spin_unlock_irq(&current->sighand->siglock);
500

501
	/* we really need to bite the bullet and change layout */
502
	ac->ac_uid = from_kuid_munged(file->f_cred->user_ns, current_uid());
503
	ac->ac_gid = from_kgid_munged(file->f_cred->user_ns, current_gid());
504
#if ACCT_VERSION == 1 || ACCT_VERSION == 2
505
	/* backward-compatible 16 bit fields */
506
	ac->ac_uid16 = ac->ac_uid;
507
	ac->ac_gid16 = ac->ac_gid;
508
#elif ACCT_VERSION == 3
509
	{
510
		struct pid_namespace *ns = acct->ns;
511

512
		ac->ac_pid = task_tgid_nr_ns(current, ns);
513
		rcu_read_lock();
514
		ac->ac_ppid = task_tgid_nr_ns(rcu_dereference(current->real_parent), ns);
515
		rcu_read_unlock();
516
	}
517
#endif
518
}
519

520
static void acct_write_process(struct bsd_acct_struct *acct)
521
{
522
	struct file *file = acct->file;
523
	const struct cred *cred;
524
	acct_t *ac = &acct->ac;
525

526
	/* Perform file operations on behalf of whoever enabled accounting */
527
	cred = override_creds(file->f_cred);
528

529
	/*
530
	 * First check to see if there is enough free_space to continue
531
	 * the process accounting system. Then get freeze protection. If
532
	 * the fs is frozen, just skip the write as we could deadlock
533
	 * the system otherwise.
534
	 */
535
	if (check_free_space(acct) && file_start_write_trylock(file)) {
536
		/* it's been opened O_APPEND, so position is irrelevant */
537
		loff_t pos = 0;
538
		__kernel_write(file, ac, sizeof(acct_t), &pos);
539
		file_end_write(file);
540
	}
541

542
	revert_creds(cred);
543
}
544

545
static void do_acct_process(struct bsd_acct_struct *acct)
546
{
547
	unsigned long flim;
548

549
	/* Accounting records are not subject to resource limits. */
550
	flim = rlimit(RLIMIT_FSIZE);
551
	current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
552
	fill_ac(acct);
553
	acct_write_process(acct);
554
	current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim;
555
}
556

557
/**
558
 * acct_collect - collect accounting information into pacct_struct
559
 * @exitcode: task exit code
560
 * @group_dead: not 0, if this thread is the last one in the process.
561
 */
562
void acct_collect(long exitcode, int group_dead)
563
{
564
	struct pacct_struct *pacct = &current->signal->pacct;
565
	u64 utime, stime;
566
	unsigned long vsize = 0;
567

568
	if (group_dead && current->mm) {
569
		struct mm_struct *mm = current->mm;
570
		VMA_ITERATOR(vmi, mm, 0);
571
		struct vm_area_struct *vma;
572

573
		mmap_read_lock(mm);
574
		for_each_vma(vmi, vma)
575
			vsize += vma->vm_end - vma->vm_start;
576
		mmap_read_unlock(mm);
577
	}
578

579
	spin_lock_irq(&current->sighand->siglock);
580
	if (group_dead)
581
		pacct->ac_mem = vsize / 1024;
582
	if (thread_group_leader(current)) {
583
		pacct->ac_exitcode = exitcode;
584
		if (current->flags & PF_FORKNOEXEC)
585
			pacct->ac_flag |= AFORK;
586
	}
587
	if (current->flags & PF_SUPERPRIV)
588
		pacct->ac_flag |= ASU;
589
	if (current->flags & PF_DUMPCORE)
590
		pacct->ac_flag |= ACORE;
591
	if (current->flags & PF_SIGNALED)
592
		pacct->ac_flag |= AXSIG;
593

594
	task_cputime(current, &utime, &stime);
595
	pacct->ac_utime += utime;
596
	pacct->ac_stime += stime;
597
	pacct->ac_minflt += current->min_flt;
598
	pacct->ac_majflt += current->maj_flt;
599
	spin_unlock_irq(&current->sighand->siglock);
600
}
601

602
static void slow_acct_process(struct pid_namespace *ns)
603
{
604
	for ( ; ns; ns = ns->parent) {
605
		struct bsd_acct_struct *acct = acct_get(ns);
606
		if (acct) {
607
			do_acct_process(acct);
608
			mutex_unlock(&acct->lock);
609
			acct_put(acct);
610
		}
611
	}
612
}
613

614
/**
615
 * acct_process - handles process accounting for an exiting task
616
 */
617
void acct_process(void)
618
{
619
	struct pid_namespace *ns;
620

621
	/*
622
	 * This loop is safe lockless, since current is still
623
	 * alive and holds its namespace, which in turn holds
624
	 * its parent.
625
	 */
626
	for (ns = task_active_pid_ns(current); ns != NULL; ns = ns->parent) {
627
		if (ns->bacct)
628
			break;
629
	}
630
	if (unlikely(ns))
631
		slow_acct_process(ns);
632
}
633

634