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 <mvw@planets.elm.net>
8 *
9 *  Some code based on ideas and code from:
10 *  Thomas K. Dyas <tdyas@eden.rutgers.edu>
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/mm.h>
48#include <linux/slab.h>
49#include <linux/acct.h>
50#include <linux/capability.h>
51#include <linux/file.h>
52#include <linux/tty.h>
53#include <linux/security.h>
54#include <linux/vfs.h>
55#include <linux/jiffies.h>
56#include <linux/times.h>
57#include <linux/syscalls.h>
58#include <linux/mount.h>
59#include <linux/uaccess.h>
60#include <linux/sched/cputime.h>
61
62#include <asm/div64.h>
63#include <linux/pid_namespace.h>
64#include <linux/fs_pin.h>
65
66/*
67 * These constants control the amount of freespace that suspend and
68 * resume the process accounting system, and the time delay between
69 * each check.
70 * Turned into sysctl-controllable parameters. AV, 12/11/98
71 */
72
73static int acct_parm[3] = {4, 2, 30};
74#define RESUME		(acct_parm[0])	/* >foo% free space - resume */
75#define SUSPEND		(acct_parm[1])	/* <foo% free space - suspend */
76#define ACCT_TIMEOUT	(acct_parm[2])	/* foo second timeout between checks */
77
78#ifdef CONFIG_SYSCTL
79static struct ctl_table kern_acct_table[] = {
80	{
81		.procname       = "acct",
82		.data           = &acct_parm,
83		.maxlen         = 3*sizeof(int),
84		.mode           = 0644,
85		.proc_handler   = proc_dointvec,
86	},
87	{ }
88};
89
90static __init int kernel_acct_sysctls_init(void)
91{
92	register_sysctl_init("kernel", kern_acct_table);
93	return 0;
94}
95late_initcall(kernel_acct_sysctls_init);
96#endif /* CONFIG_SYSCTL */
97
98/*
99 * External references and all of the globals.
100 */
101
102struct bsd_acct_struct {
103	struct fs_pin		pin;
104	atomic_long_t		count;
105	struct rcu_head		rcu;
106	struct mutex		lock;
107	int			active;
108	unsigned long		needcheck;
109	struct file		*file;
110	struct pid_namespace	*ns;
111	struct work_struct	work;
112	struct completion	done;
113};
114
115static void do_acct_process(struct bsd_acct_struct *acct);
116
117/*
118 * Check the amount of free space and suspend/resume accordingly.
119 */
120static int check_free_space(struct bsd_acct_struct *acct)
121{
122	struct kstatfs sbuf;
123
124	if (time_is_after_jiffies(acct->needcheck))
125		goto out;
126
127	/* May block */
128	if (vfs_statfs(&acct->file->f_path, &sbuf))
129		goto out;
130
131	if (acct->active) {
132		u64 suspend = sbuf.f_blocks * SUSPEND;
133		do_div(suspend, 100);
134		if (sbuf.f_bavail <= suspend) {
135			acct->active = 0;
136			pr_info("Process accounting paused\n");
137		}
138	} else {
139		u64 resume = sbuf.f_blocks * RESUME;
140		do_div(resume, 100);
141		if (sbuf.f_bavail >= resume) {
142			acct->active = 1;
143			pr_info("Process accounting resumed\n");
144		}
145	}
146
147	acct->needcheck = jiffies + ACCT_TIMEOUT*HZ;
148out:
149	return acct->active;
150}
151
152static void acct_put(struct bsd_acct_struct *p)
153{
154	if (atomic_long_dec_and_test(&p->count))
155		kfree_rcu(p, rcu);
156}
157
158static inline struct bsd_acct_struct *to_acct(struct fs_pin *p)
159{
160	return p ? container_of(p, struct bsd_acct_struct, pin) : NULL;
161}
162
163static struct bsd_acct_struct *acct_get(struct pid_namespace *ns)
164{
165	struct bsd_acct_struct *res;
166again:
167	smp_rmb();
168	rcu_read_lock();
169	res = to_acct(READ_ONCE(ns->bacct));
170	if (!res) {
171		rcu_read_unlock();
172		return NULL;
173	}
174	if (!atomic_long_inc_not_zero(&res->count)) {
175		rcu_read_unlock();
176		cpu_relax();
177		goto again;
178	}
179	rcu_read_unlock();
180	mutex_lock(&res->lock);
181	if (res != to_acct(READ_ONCE(ns->bacct))) {
182		mutex_unlock(&res->lock);
183		acct_put(res);
184		goto again;
185	}
186	return res;
187}
188
189static void acct_pin_kill(struct fs_pin *pin)
190{
191	struct bsd_acct_struct *acct = to_acct(pin);
192	mutex_lock(&acct->lock);
193	do_acct_process(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
202static 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	if (file->f_op->flush)
207		file->f_op->flush(file, NULL);
208	__fput_sync(file);
209	complete(&acct->done);
210}
211
212static int acct_on(struct filename *pathname)
213{
214	struct file *file;
215	struct vfsmount *mnt, *internal;
216	struct pid_namespace *ns = task_active_pid_ns(current);
217	struct bsd_acct_struct *acct;
218	struct fs_pin *old;
219	int err;
220
221	acct = kzalloc(sizeof(struct bsd_acct_struct), GFP_KERNEL);
222	if (!acct)
223		return -ENOMEM;
224
225	/* Difference from BSD - they don't do O_APPEND */
226	file = file_open_name(pathname, O_WRONLY|O_APPEND|O_LARGEFILE, 0);
227	if (IS_ERR(file)) {
228		kfree(acct);
229		return PTR_ERR(file);
230	}
231
232	if (!S_ISREG(file_inode(file)->i_mode)) {
233		kfree(acct);
234		filp_close(file, NULL);
235		return -EACCES;
236	}
237
238	if (!(file->f_mode & FMODE_CAN_WRITE)) {
239		kfree(acct);
240		filp_close(file, NULL);
241		return -EIO;
242	}
243	internal = mnt_clone_internal(&file->f_path);
244	if (IS_ERR(internal)) {
245		kfree(acct);
246		filp_close(file, NULL);
247		return PTR_ERR(internal);
248	}
249	err = mnt_get_write_access(internal);
250	if (err) {
251		mntput(internal);
252		kfree(acct);
253		filp_close(file, NULL);
254		return err;
255	}
256	mnt = file->f_path.mnt;
257	file->f_path.mnt = internal;
258
259	atomic_long_set(&acct->count, 1);
260	init_fs_pin(&acct->pin, acct_pin_kill);
261	acct->file = file;
262	acct->needcheck = jiffies;
263	acct->ns = ns;
264	mutex_init(&acct->lock);
265	INIT_WORK(&acct->work, close_work);
266	init_completion(&acct->done);
267	mutex_lock_nested(&acct->lock, 1);	/* nobody has seen it yet */
268	pin_insert(&acct->pin, mnt);
269
270	rcu_read_lock();
271	old = xchg(&ns->bacct, &acct->pin);
272	mutex_unlock(&acct->lock);
273	pin_kill(old);
274	mnt_put_write_access(mnt);
275	mntput(mnt);
276	return 0;
277}
278
279static DEFINE_MUTEX(acct_on_mutex);
280
281/**
282 * sys_acct - enable/disable process accounting
283 * @name: file name for accounting records or NULL to shutdown accounting
284 *
285 * sys_acct() is the only system call needed to implement process
286 * accounting. It takes the name of the file where accounting records
287 * should be written. If the filename is NULL, accounting will be
288 * shutdown.
289 *
290 * Returns: 0 for success or negative errno values for failure.
291 */
292SYSCALL_DEFINE1(acct, const char __user *, name)
293{
294	int error = 0;
295
296	if (!capable(CAP_SYS_PACCT))
297		return -EPERM;
298
299	if (name) {
300		struct filename *tmp = getname(name);
301
302		if (IS_ERR(tmp))
303			return PTR_ERR(tmp);
304		mutex_lock(&acct_on_mutex);
305		error = acct_on(tmp);
306		mutex_unlock(&acct_on_mutex);
307		putname(tmp);
308	} else {
309		rcu_read_lock();
310		pin_kill(task_active_pid_ns(current)->bacct);
311	}
312
313	return error;
314}
315
316void acct_exit_ns(struct pid_namespace *ns)
317{
318	rcu_read_lock();
319	pin_kill(ns->bacct);
320}
321
322/*
323 *  encode an u64 into a comp_t
324 *
325 *  This routine has been adopted from the encode_comp_t() function in
326 *  the kern_acct.c file of the FreeBSD operating system. The encoding
327 *  is a 13-bit fraction with a 3-bit (base 8) exponent.
328 */
329
330#define	MANTSIZE	13			/* 13 bit mantissa. */
331#define	EXPSIZE		3			/* Base 8 (3 bit) exponent. */
332#define	MAXFRACT	((1 << MANTSIZE) - 1)	/* Maximum fractional value. */
333
334static comp_t encode_comp_t(u64 value)
335{
336	int exp, rnd;
337
338	exp = rnd = 0;
339	while (value > MAXFRACT) {
340		rnd = value & (1 << (EXPSIZE - 1));	/* Round up? */
341		value >>= EXPSIZE;	/* Base 8 exponent == 3 bit shift. */
342		exp++;
343	}
344
345	/*
346	 * If we need to round up, do it (and handle overflow correctly).
347	 */
348	if (rnd && (++value > MAXFRACT)) {
349		value >>= EXPSIZE;
350		exp++;
351	}
352
353	if (exp > (((comp_t) ~0U) >> MANTSIZE))
354		return (comp_t) ~0U;
355	/*
356	 * Clean it up and polish it off.
357	 */
358	exp <<= MANTSIZE;		/* Shift the exponent into place */
359	exp += value;			/* and add on the mantissa. */
360	return exp;
361}
362
363#if ACCT_VERSION == 1 || ACCT_VERSION == 2
364/*
365 * encode an u64 into a comp2_t (24 bits)
366 *
367 * Format: 5 bit base 2 exponent, 20 bits mantissa.
368 * The leading bit of the mantissa is not stored, but implied for
369 * non-zero exponents.
370 * Largest encodable value is 50 bits.
371 */
372
373#define MANTSIZE2       20                      /* 20 bit mantissa. */
374#define EXPSIZE2        5                       /* 5 bit base 2 exponent. */
375#define MAXFRACT2       ((1ul << MANTSIZE2) - 1) /* Maximum fractional value. */
376#define MAXEXP2         ((1 << EXPSIZE2) - 1)    /* Maximum exponent. */
377
378static comp2_t encode_comp2_t(u64 value)
379{
380	int exp, rnd;
381
382	exp = (value > (MAXFRACT2>>1));
383	rnd = 0;
384	while (value > MAXFRACT2) {
385		rnd = value & 1;
386		value >>= 1;
387		exp++;
388	}
389
390	/*
391	 * If we need to round up, do it (and handle overflow correctly).
392	 */
393	if (rnd && (++value > MAXFRACT2)) {
394		value >>= 1;
395		exp++;
396	}
397
398	if (exp > MAXEXP2) {
399		/* Overflow. Return largest representable number instead. */
400		return (1ul << (MANTSIZE2+EXPSIZE2-1)) - 1;
401	} else {
402		return (value & (MAXFRACT2>>1)) | (exp << (MANTSIZE2-1));
403	}
404}
405#elif ACCT_VERSION == 3
406/*
407 * encode an u64 into a 32 bit IEEE float
408 */
409static u32 encode_float(u64 value)
410{
411	unsigned exp = 190;
412	unsigned u;
413
414	if (value == 0)
415		return 0;
416	while ((s64)value > 0) {
417		value <<= 1;
418		exp--;
419	}
420	u = (u32)(value >> 40) & 0x7fffffu;
421	return u | (exp << 23);
422}
423#endif
424
425/*
426 *  Write an accounting entry for an exiting process
427 *
428 *  The acct_process() call is the workhorse of the process
429 *  accounting system. The struct acct is built here and then written
430 *  into the accounting file. This function should only be called from
431 *  do_exit() or when switching to a different output file.
432 */
433
434static void fill_ac(acct_t *ac)
435{
436	struct pacct_struct *pacct = &current->signal->pacct;
437	u64 elapsed, run_time;
438	time64_t btime;
439	struct tty_struct *tty;
440
441	/*
442	 * Fill the accounting struct with the needed info as recorded
443	 * by the different kernel functions.
444	 */
445	memset(ac, 0, sizeof(acct_t));
446
447	ac->ac_version = ACCT_VERSION | ACCT_BYTEORDER;
448	strscpy(ac->ac_comm, current->comm, sizeof(ac->ac_comm));
449
450	/* calculate run_time in nsec*/
451	run_time = ktime_get_ns();
452	run_time -= current->group_leader->start_time;
453	/* convert nsec -> AHZ */
454	elapsed = nsec_to_AHZ(run_time);
455#if ACCT_VERSION == 3
456	ac->ac_etime = encode_float(elapsed);
457#else
458	ac->ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ?
459				(unsigned long) elapsed : (unsigned long) -1l);
460#endif
461#if ACCT_VERSION == 1 || ACCT_VERSION == 2
462	{
463		/* new enlarged etime field */
464		comp2_t etime = encode_comp2_t(elapsed);
465
466		ac->ac_etime_hi = etime >> 16;
467		ac->ac_etime_lo = (u16) etime;
468	}
469#endif
470	do_div(elapsed, AHZ);
471	btime = ktime_get_real_seconds() - elapsed;
472	ac->ac_btime = clamp_t(time64_t, btime, 0, U32_MAX);
473#if ACCT_VERSION == 2
474	ac->ac_ahz = AHZ;
475#endif
476
477	spin_lock_irq(&current->sighand->siglock);
478	tty = current->signal->tty;	/* Safe as we hold the siglock */
479	ac->ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0;
480	ac->ac_utime = encode_comp_t(nsec_to_AHZ(pacct->ac_utime));
481	ac->ac_stime = encode_comp_t(nsec_to_AHZ(pacct->ac_stime));
482	ac->ac_flag = pacct->ac_flag;
483	ac->ac_mem = encode_comp_t(pacct->ac_mem);
484	ac->ac_minflt = encode_comp_t(pacct->ac_minflt);
485	ac->ac_majflt = encode_comp_t(pacct->ac_majflt);
486	ac->ac_exitcode = pacct->ac_exitcode;
487	spin_unlock_irq(&current->sighand->siglock);
488}
489/*
490 *  do_acct_process does all actual work. Caller holds the reference to file.
491 */
492static void do_acct_process(struct bsd_acct_struct *acct)
493{
494	acct_t ac;
495	unsigned long flim;
496	const struct cred *orig_cred;
497	struct file *file = acct->file;
498
499	/*
500	 * Accounting records are not subject to resource limits.
501	 */
502	flim = rlimit(RLIMIT_FSIZE);
503	current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
504	/* Perform file operations on behalf of whoever enabled accounting */
505	orig_cred = override_creds(file->f_cred);
506
507	/*
508	 * First check to see if there is enough free_space to continue
509	 * the process accounting system.
510	 */
511	if (!check_free_space(acct))
512		goto out;
513
514	fill_ac(&ac);
515	/* we really need to bite the bullet and change layout */
516	ac.ac_uid = from_kuid_munged(file->f_cred->user_ns, orig_cred->uid);
517	ac.ac_gid = from_kgid_munged(file->f_cred->user_ns, orig_cred->gid);
518#if ACCT_VERSION == 1 || ACCT_VERSION == 2
519	/* backward-compatible 16 bit fields */
520	ac.ac_uid16 = ac.ac_uid;
521	ac.ac_gid16 = ac.ac_gid;
522#elif ACCT_VERSION == 3
523	{
524		struct pid_namespace *ns = acct->ns;
525
526		ac.ac_pid = task_tgid_nr_ns(current, ns);
527		rcu_read_lock();
528		ac.ac_ppid = task_tgid_nr_ns(rcu_dereference(current->real_parent),
529					     ns);
530		rcu_read_unlock();
531	}
532#endif
533	/*
534	 * Get freeze protection. If the fs is frozen, just skip the write
535	 * as we could deadlock the system otherwise.
536	 */
537	if (file_start_write_trylock(file)) {
538		/* it's been opened O_APPEND, so position is irrelevant */
539		loff_t pos = 0;
540		__kernel_write(file, &ac, sizeof(acct_t), &pos);
541		file_end_write(file);
542	}
543out:
544	current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim;
545	revert_creds(orig_cred);
546}
547
548/**
549 * acct_collect - collect accounting information into pacct_struct
550 * @exitcode: task exit code
551 * @group_dead: not 0, if this thread is the last one in the process.
552 */
553void acct_collect(long exitcode, int group_dead)
554{
555	struct pacct_struct *pacct = &current->signal->pacct;
556	u64 utime, stime;
557	unsigned long vsize = 0;
558
559	if (group_dead && current->mm) {
560		struct mm_struct *mm = current->mm;
561		VMA_ITERATOR(vmi, mm, 0);
562		struct vm_area_struct *vma;
563
564		mmap_read_lock(mm);
565		for_each_vma(vmi, vma)
566			vsize += vma->vm_end - vma->vm_start;
567		mmap_read_unlock(mm);
568	}
569
570	spin_lock_irq(&current->sighand->siglock);
571	if (group_dead)
572		pacct->ac_mem = vsize / 1024;
573	if (thread_group_leader(current)) {
574		pacct->ac_exitcode = exitcode;
575		if (current->flags & PF_FORKNOEXEC)
576			pacct->ac_flag |= AFORK;
577	}
578	if (current->flags & PF_SUPERPRIV)
579		pacct->ac_flag |= ASU;
580	if (current->flags & PF_DUMPCORE)
581		pacct->ac_flag |= ACORE;
582	if (current->flags & PF_SIGNALED)
583		pacct->ac_flag |= AXSIG;
584
585	task_cputime(current, &utime, &stime);
586	pacct->ac_utime += utime;
587	pacct->ac_stime += stime;
588	pacct->ac_minflt += current->min_flt;
589	pacct->ac_majflt += current->maj_flt;
590	spin_unlock_irq(&current->sighand->siglock);
591}
592
593static void slow_acct_process(struct pid_namespace *ns)
594{
595	for ( ; ns; ns = ns->parent) {
596		struct bsd_acct_struct *acct = acct_get(ns);
597		if (acct) {
598			do_acct_process(acct);
599			mutex_unlock(&acct->lock);
600			acct_put(acct);
601		}
602	}
603}
604
605/**
606 * acct_process - handles process accounting for an exiting task
607 */
608void acct_process(void)
609{
610	struct pid_namespace *ns;
611
612	/*
613	 * This loop is safe lockless, since current is still
614	 * alive and holds its namespace, which in turn holds
615	 * its parent.
616	 */
617	for (ns = task_active_pid_ns(current); ns != NULL; ns = ns->parent) {
618		if (ns->bacct)
619			break;
620	}
621	if (unlikely(ns))
622		slow_acct_process(ns);
623}
624