projects/linux·blob v5.7 · refs

608 lines · 15.5 KiB

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 with sys_umount(). If the accointing
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_sem 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/blkdev.h> /* sector_div */
64#include <linux/pid_namespace.h>
65#include <linux/fs_pin.h>
66
67/*
68 * These constants control the amount of freespace that suspend and
69 * resume the process accounting system, and the time delay between
70 * each check.
71 * Turned into sysctl-controllable parameters. AV, 12/11/98
72 */
73
74int acct_parm[3] = {4, 2, 30};
75#define RESUME (acct_parm[0]) /* >foo% free space - resume */
76#define SUSPEND (acct_parm[1]) /* <foo% free space - suspend */
77#define ACCT_TIMEOUT (acct_parm[2]) /* foo second timeout between checks */
78
79/*
80 * External references and all of the globals.
81 */
82
83struct bsd_acct_struct {
84 struct fs_pin pin;
85 atomic_long_t count;
86 struct rcu_head rcu;
87 struct mutex lock;
88 int active;
89 unsigned long needcheck;
90 struct file *file;
91 struct pid_namespace *ns;
92 struct work_struct work;
93 struct completion done;
94};
95
96static void do_acct_process(struct bsd_acct_struct *acct);
97
98/*
99 * Check the amount of free space and suspend/resume accordingly.
100 */
101static int check_free_space(struct bsd_acct_struct *acct)
102{
103 struct kstatfs sbuf;
104
105 if (time_is_after_jiffies(acct->needcheck))
106 goto out;
107
108 /* May block */
109 if (vfs_statfs(&acct->file->f_path, &sbuf))
110 goto out;
111
112 if (acct->active) {
113 u64 suspend = sbuf.f_blocks * SUSPEND;
114 do_div(suspend, 100);
115 if (sbuf.f_bavail <= suspend) {
116 acct->active = 0;
117 pr_info("Process accounting paused\n");
118 }
119 } else {
120 u64 resume = sbuf.f_blocks * RESUME;
121 do_div(resume, 100);
122 if (sbuf.f_bavail >= resume) {
123 acct->active = 1;
124 pr_info("Process accounting resumed\n");
125 }
126 }
127
128 acct->needcheck = jiffies + ACCT_TIMEOUT*HZ;
129out:
130 return acct->active;
131}
132
133static void acct_put(struct bsd_acct_struct *p)
134{
135 if (atomic_long_dec_and_test(&p->count))
136 kfree_rcu(p, rcu);
137}
138
139static inline struct bsd_acct_struct *to_acct(struct fs_pin *p)
140{
141 return p ? container_of(p, struct bsd_acct_struct, pin) : NULL;
142}
143
144static struct bsd_acct_struct *acct_get(struct pid_namespace *ns)
145{
146 struct bsd_acct_struct *res;
147again:
148 smp_rmb();
149 rcu_read_lock();
150 res = to_acct(READ_ONCE(ns->bacct));
151 if (!res) {
152 rcu_read_unlock();
153 return NULL;
154 }
155 if (!atomic_long_inc_not_zero(&res->count)) {
156 rcu_read_unlock();
157 cpu_relax();
158 goto again;
159 }
160 rcu_read_unlock();
161 mutex_lock(&res->lock);
162 if (res != to_acct(READ_ONCE(ns->bacct))) {
163 mutex_unlock(&res->lock);
164 acct_put(res);
165 goto again;
166 }
167 return res;
168}
169
170static void acct_pin_kill(struct fs_pin *pin)
171{
172 struct bsd_acct_struct *acct = to_acct(pin);
173 mutex_lock(&acct->lock);
174 do_acct_process(acct);
175 schedule_work(&acct->work);
176 wait_for_completion(&acct->done);
177 cmpxchg(&acct->ns->bacct, pin, NULL);
178 mutex_unlock(&acct->lock);
179 pin_remove(pin);
180 acct_put(acct);
181}
182
183static void close_work(struct work_struct *work)
184{
185 struct bsd_acct_struct *acct = container_of(work, struct bsd_acct_struct, work);
186 struct file *file = acct->file;
187 if (file->f_op->flush)
188 file->f_op->flush(file, NULL);
189 __fput_sync(file);
190 complete(&acct->done);
191}
192
193static int acct_on(struct filename *pathname)
194{
195 struct file *file;
196 struct vfsmount *mnt, *internal;
197 struct pid_namespace *ns = task_active_pid_ns(current);
198 struct bsd_acct_struct *acct;
199 struct fs_pin *old;
200 int err;
201
202 acct = kzalloc(sizeof(struct bsd_acct_struct), GFP_KERNEL);
203 if (!acct)
204 return -ENOMEM;
205
206 /* Difference from BSD - they don't do O_APPEND */
207 file = file_open_name(pathname, O_WRONLY|O_APPEND|O_LARGEFILE, 0);
208 if (IS_ERR(file)) {
209 kfree(acct);
210 return PTR_ERR(file);
211 }
212
213 if (!S_ISREG(file_inode(file)->i_mode)) {
214 kfree(acct);
215 filp_close(file, NULL);
216 return -EACCES;
217 }
218
219 if (!(file->f_mode & FMODE_CAN_WRITE)) {
220 kfree(acct);
221 filp_close(file, NULL);
222 return -EIO;
223 }
224 internal = mnt_clone_internal(&file->f_path);
225 if (IS_ERR(internal)) {
226 kfree(acct);
227 filp_close(file, NULL);
228 return PTR_ERR(internal);
229 }
230 err = __mnt_want_write(internal);
231 if (err) {
232 mntput(internal);
233 kfree(acct);
234 filp_close(file, NULL);
235 return err;
236 }
237 mnt = file->f_path.mnt;
238 file->f_path.mnt = internal;
239
240 atomic_long_set(&acct->count, 1);
241 init_fs_pin(&acct->pin, acct_pin_kill);
242 acct->file = file;
243 acct->needcheck = jiffies;
244 acct->ns = ns;
245 mutex_init(&acct->lock);
246 INIT_WORK(&acct->work, close_work);
247 init_completion(&acct->done);
248 mutex_lock_nested(&acct->lock, 1); /* nobody has seen it yet */
249 pin_insert(&acct->pin, mnt);
250
251 rcu_read_lock();
252 old = xchg(&ns->bacct, &acct->pin);
253 mutex_unlock(&acct->lock);
254 pin_kill(old);
255 __mnt_drop_write(mnt);
256 mntput(mnt);
257 return 0;
258}
259
260static DEFINE_MUTEX(acct_on_mutex);
261
262/**
263 * sys_acct - enable/disable process accounting
264 * @name: file name for accounting records or NULL to shutdown accounting
265 *
266 * Returns 0 for success or negative errno values for failure.
267 *
268 * sys_acct() is the only system call needed to implement process
269 * accounting. It takes the name of the file where accounting records
270 * should be written. If the filename is NULL, accounting will be
271 * shutdown.
272 */
273SYSCALL_DEFINE1(acct, const char __user *, name)
274{
275 int error = 0;
276
277 if (!capable(CAP_SYS_PACCT))
278 return -EPERM;
279
280 if (name) {
281 struct filename *tmp = getname(name);
282
283 if (IS_ERR(tmp))
284 return PTR_ERR(tmp);
285 mutex_lock(&acct_on_mutex);
286 error = acct_on(tmp);
287 mutex_unlock(&acct_on_mutex);
288 putname(tmp);
289 } else {
290 rcu_read_lock();
291 pin_kill(task_active_pid_ns(current)->bacct);
292 }
293
294 return error;
295}
296
297void acct_exit_ns(struct pid_namespace *ns)
298{
299 rcu_read_lock();
300 pin_kill(ns->bacct);
301}
302
303/*
304 * encode an unsigned long into a comp_t
305 *
306 * This routine has been adopted from the encode_comp_t() function in
307 * the kern_acct.c file of the FreeBSD operating system. The encoding
308 * is a 13-bit fraction with a 3-bit (base 8) exponent.
309 */
310
311#define MANTSIZE 13 /* 13 bit mantissa. */
312#define EXPSIZE 3 /* Base 8 (3 bit) exponent. */
313#define MAXFRACT ((1 << MANTSIZE) - 1) /* Maximum fractional value. */
314
315static comp_t encode_comp_t(unsigned long value)
316{
317 int exp, rnd;
318
319 exp = rnd = 0;
320 while (value > MAXFRACT) {
321 rnd = value & (1 << (EXPSIZE - 1)); /* Round up? */
322 value >>= EXPSIZE; /* Base 8 exponent == 3 bit shift. */
323 exp++;
324 }
325
326 /*
327 * If we need to round up, do it (and handle overflow correctly).
328 */
329 if (rnd && (++value > MAXFRACT)) {
330 value >>= EXPSIZE;
331 exp++;
332 }
333
334 /*
335 * Clean it up and polish it off.
336 */
337 exp <<= MANTSIZE; /* Shift the exponent into place */
338 exp += value; /* and add on the mantissa. */
339 return exp;
340}
341
342#if ACCT_VERSION == 1 || ACCT_VERSION == 2
343/*
344 * encode an u64 into a comp2_t (24 bits)
345 *
346 * Format: 5 bit base 2 exponent, 20 bits mantissa.
347 * The leading bit of the mantissa is not stored, but implied for
348 * non-zero exponents.
349 * Largest encodable value is 50 bits.
350 */
351
352#define MANTSIZE2 20 /* 20 bit mantissa. */
353#define EXPSIZE2 5 /* 5 bit base 2 exponent. */
354#define MAXFRACT2 ((1ul << MANTSIZE2) - 1) /* Maximum fractional value. */
355#define MAXEXP2 ((1 << EXPSIZE2) - 1) /* Maximum exponent. */
356
357static comp2_t encode_comp2_t(u64 value)
358{
359 int exp, rnd;
360
361 exp = (value > (MAXFRACT2>>1));
362 rnd = 0;
363 while (value > MAXFRACT2) {
364 rnd = value & 1;
365 value >>= 1;
366 exp++;
367 }
368
369 /*
370 * If we need to round up, do it (and handle overflow correctly).
371 */
372 if (rnd && (++value > MAXFRACT2)) {
373 value >>= 1;
374 exp++;
375 }
376
377 if (exp > MAXEXP2) {
378 /* Overflow. Return largest representable number instead. */
379 return (1ul << (MANTSIZE2+EXPSIZE2-1)) - 1;
380 } else {
381 return (value & (MAXFRACT2>>1)) | (exp << (MANTSIZE2-1));
382 }
383}
384#endif
385
386#if ACCT_VERSION == 3
387/*
388 * encode an u64 into a 32 bit IEEE float
389 */
390static u32 encode_float(u64 value)
391{
392 unsigned exp = 190;
393 unsigned u;
394
395 if (value == 0)
396 return 0;
397 while ((s64)value > 0) {
398 value <<= 1;
399 exp--;
400 }
401 u = (u32)(value >> 40) & 0x7fffffu;
402 return u | (exp << 23);
403}
404#endif
405
406/*
407 * Write an accounting entry for an exiting process
408 *
409 * The acct_process() call is the workhorse of the process
410 * accounting system. The struct acct is built here and then written
411 * into the accounting file. This function should only be called from
412 * do_exit() or when switching to a different output file.
413 */
414
415static void fill_ac(acct_t *ac)
416{
417 struct pacct_struct *pacct = &current->signal->pacct;
418 u64 elapsed, run_time;
419 time64_t btime;
420 struct tty_struct *tty;
421
422 /*
423 * Fill the accounting struct with the needed info as recorded
424 * by the different kernel functions.
425 */
426 memset(ac, 0, sizeof(acct_t));
427
428 ac->ac_version = ACCT_VERSION | ACCT_BYTEORDER;
429 strlcpy(ac->ac_comm, current->comm, sizeof(ac->ac_comm));
430
431 /* calculate run_time in nsec*/
432 run_time = ktime_get_ns();
433 run_time -= current->group_leader->start_time;
434 /* convert nsec -> AHZ */
435 elapsed = nsec_to_AHZ(run_time);
436#if ACCT_VERSION == 3
437 ac->ac_etime = encode_float(elapsed);
438#else
439 ac->ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ?
440 (unsigned long) elapsed : (unsigned long) -1l);
441#endif
442#if ACCT_VERSION == 1 || ACCT_VERSION == 2
443 {
444 /* new enlarged etime field */
445 comp2_t etime = encode_comp2_t(elapsed);
446
447 ac->ac_etime_hi = etime >> 16;
448 ac->ac_etime_lo = (u16) etime;
449 }
450#endif
451 do_div(elapsed, AHZ);
452 btime = ktime_get_real_seconds() - elapsed;
453 ac->ac_btime = clamp_t(time64_t, btime, 0, U32_MAX);
454#if ACCT_VERSION==2
455 ac->ac_ahz = AHZ;
456#endif
457
458 spin_lock_irq(&current->sighand->siglock);
459 tty = current->signal->tty; /* Safe as we hold the siglock */
460 ac->ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0;
461 ac->ac_utime = encode_comp_t(nsec_to_AHZ(pacct->ac_utime));
462 ac->ac_stime = encode_comp_t(nsec_to_AHZ(pacct->ac_stime));
463 ac->ac_flag = pacct->ac_flag;
464 ac->ac_mem = encode_comp_t(pacct->ac_mem);
465 ac->ac_minflt = encode_comp_t(pacct->ac_minflt);
466 ac->ac_majflt = encode_comp_t(pacct->ac_majflt);
467 ac->ac_exitcode = pacct->ac_exitcode;
468 spin_unlock_irq(&current->sighand->siglock);
469}
470/*
471 * do_acct_process does all actual work. Caller holds the reference to file.
472 */
473static void do_acct_process(struct bsd_acct_struct *acct)
474{
475 acct_t ac;
476 unsigned long flim;
477 const struct cred *orig_cred;
478 struct file *file = acct->file;
479
480 /*
481 * Accounting records are not subject to resource limits.
482 */
483 flim = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
484 current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
485 /* Perform file operations on behalf of whoever enabled accounting */
486 orig_cred = override_creds(file->f_cred);
487
488 /*
489 * First check to see if there is enough free_space to continue
490 * the process accounting system.
491 */
492 if (!check_free_space(acct))
493 goto out;
494
495 fill_ac(&ac);
496 /* we really need to bite the bullet and change layout */
497 ac.ac_uid = from_kuid_munged(file->f_cred->user_ns, orig_cred->uid);
498 ac.ac_gid = from_kgid_munged(file->f_cred->user_ns, orig_cred->gid);
499#if ACCT_VERSION == 1 || ACCT_VERSION == 2
500 /* backward-compatible 16 bit fields */
501 ac.ac_uid16 = ac.ac_uid;
502 ac.ac_gid16 = ac.ac_gid;
503#endif
504#if ACCT_VERSION == 3
505 {
506 struct pid_namespace *ns = acct->ns;
507
508 ac.ac_pid = task_tgid_nr_ns(current, ns);
509 rcu_read_lock();
510 ac.ac_ppid = task_tgid_nr_ns(rcu_dereference(current->real_parent),
511 ns);
512 rcu_read_unlock();
513 }
514#endif
515 /*
516 * Get freeze protection. If the fs is frozen, just skip the write
517 * as we could deadlock the system otherwise.
518 */
519 if (file_start_write_trylock(file)) {
520 /* it's been opened O_APPEND, so position is irrelevant */
521 loff_t pos = 0;
522 __kernel_write(file, &ac, sizeof(acct_t), &pos);
523 file_end_write(file);
524 }
525out:
526 current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim;
527 revert_creds(orig_cred);
528}
529
530/**
531 * acct_collect - collect accounting information into pacct_struct
532 * @exitcode: task exit code
533 * @group_dead: not 0, if this thread is the last one in the process.
534 */
535void acct_collect(long exitcode, int group_dead)
536{
537 struct pacct_struct *pacct = &current->signal->pacct;
538 u64 utime, stime;
539 unsigned long vsize = 0;
540
541 if (group_dead && current->mm) {
542 struct vm_area_struct *vma;
543
544 down_read(&current->mm->mmap_sem);
545 vma = current->mm->mmap;
546 while (vma) {
547 vsize += vma->vm_end - vma->vm_start;
548 vma = vma->vm_next;
549 }
550 up_read(&current->mm->mmap_sem);
551 }
552
553 spin_lock_irq(&current->sighand->siglock);
554 if (group_dead)
555 pacct->ac_mem = vsize / 1024;
556 if (thread_group_leader(current)) {
557 pacct->ac_exitcode = exitcode;
558 if (current->flags & PF_FORKNOEXEC)
559 pacct->ac_flag |= AFORK;
560 }
561 if (current->flags & PF_SUPERPRIV)
562 pacct->ac_flag |= ASU;
563 if (current->flags & PF_DUMPCORE)
564 pacct->ac_flag |= ACORE;
565 if (current->flags & PF_SIGNALED)
566 pacct->ac_flag |= AXSIG;
567
568 task_cputime(current, &utime, &stime);
569 pacct->ac_utime += utime;
570 pacct->ac_stime += stime;
571 pacct->ac_minflt += current->min_flt;
572 pacct->ac_majflt += current->maj_flt;
573 spin_unlock_irq(&current->sighand->siglock);
574}
575
576static void slow_acct_process(struct pid_namespace *ns)
577{
578 for ( ; ns; ns = ns->parent) {
579 struct bsd_acct_struct *acct = acct_get(ns);
580 if (acct) {
581 do_acct_process(acct);
582 mutex_unlock(&acct->lock);
583 acct_put(acct);
584 }
585 }
586}
587
588/**
589 * acct_process
590 *
591 * handles process accounting for an exiting task
592 */
593void acct_process(void)
594{
595 struct pid_namespace *ns;
596
597 /*
598 * This loop is safe lockless, since current is still
599 * alive and holds its namespace, which in turn holds
600 * its parent.
601 */
602 for (ns = task_active_pid_ns(current); ns != NULL; ns = ns->parent) {
603 if (ns->bacct)
604 break;
605 }
606 if (unlikely(ns))
607 slow_acct_process(ns);
608}