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/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
74 int 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
83 struct 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
96 static void do_acct_process(struct bsd_acct_struct *acct);
97
98 /*
99 * Check the amount of free space and suspend/resume accordingly.
100 */
check_free_space(struct bsd_acct_struct * acct)101 static 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;
129 out:
130 return acct->active;
131 }
132
acct_put(struct bsd_acct_struct * p)133 static 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
to_acct(struct fs_pin * p)139 static 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
acct_get(struct pid_namespace * ns)144 static struct bsd_acct_struct *acct_get(struct pid_namespace *ns)
145 {
146 struct bsd_acct_struct *res;
147 again:
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
acct_pin_kill(struct fs_pin * pin)170 static 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
close_work(struct work_struct * work)183 static 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
acct_on(struct filename * pathname)193 static 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
260 static 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 * sys_acct() is the only system call needed to implement process
267 * accounting. It takes the name of the file where accounting records
268 * should be written. If the filename is NULL, accounting will be
269 * shutdown.
270 *
271 * Returns: 0 for success or negative errno values for failure.
272 */
SYSCALL_DEFINE1(acct,const char __user *,name)273 SYSCALL_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
acct_exit_ns(struct pid_namespace * ns)297 void 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
encode_comp_t(unsigned long value)315 static 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
encode_comp2_t(u64 value)357 static 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 #elif ACCT_VERSION == 3
385 /*
386 * encode an u64 into a 32 bit IEEE float
387 */
encode_float(u64 value)388 static u32 encode_float(u64 value)
389 {
390 unsigned exp = 190;
391 unsigned u;
392
393 if (value == 0)
394 return 0;
395 while ((s64)value > 0) {
396 value <<= 1;
397 exp--;
398 }
399 u = (u32)(value >> 40) & 0x7fffffu;
400 return u | (exp << 23);
401 }
402 #endif
403
404 /*
405 * Write an accounting entry for an exiting process
406 *
407 * The acct_process() call is the workhorse of the process
408 * accounting system. The struct acct is built here and then written
409 * into the accounting file. This function should only be called from
410 * do_exit() or when switching to a different output file.
411 */
412
fill_ac(acct_t * ac)413 static void fill_ac(acct_t *ac)
414 {
415 struct pacct_struct *pacct = ¤t->signal->pacct;
416 u64 elapsed, run_time;
417 time64_t btime;
418 struct tty_struct *tty;
419
420 /*
421 * Fill the accounting struct with the needed info as recorded
422 * by the different kernel functions.
423 */
424 memset(ac, 0, sizeof(acct_t));
425
426 ac->ac_version = ACCT_VERSION | ACCT_BYTEORDER;
427 strlcpy(ac->ac_comm, current->comm, sizeof(ac->ac_comm));
428
429 /* calculate run_time in nsec*/
430 run_time = ktime_get_ns();
431 run_time -= current->group_leader->start_time;
432 /* convert nsec -> AHZ */
433 elapsed = nsec_to_AHZ(run_time);
434 #if ACCT_VERSION == 3
435 ac->ac_etime = encode_float(elapsed);
436 #else
437 ac->ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ?
438 (unsigned long) elapsed : (unsigned long) -1l);
439 #endif
440 #if ACCT_VERSION == 1 || ACCT_VERSION == 2
441 {
442 /* new enlarged etime field */
443 comp2_t etime = encode_comp2_t(elapsed);
444
445 ac->ac_etime_hi = etime >> 16;
446 ac->ac_etime_lo = (u16) etime;
447 }
448 #endif
449 do_div(elapsed, AHZ);
450 btime = ktime_get_real_seconds() - elapsed;
451 ac->ac_btime = clamp_t(time64_t, btime, 0, U32_MAX);
452 #if ACCT_VERSION==2
453 ac->ac_ahz = AHZ;
454 #endif
455
456 spin_lock_irq(¤t->sighand->siglock);
457 tty = current->signal->tty; /* Safe as we hold the siglock */
458 ac->ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0;
459 ac->ac_utime = encode_comp_t(nsec_to_AHZ(pacct->ac_utime));
460 ac->ac_stime = encode_comp_t(nsec_to_AHZ(pacct->ac_stime));
461 ac->ac_flag = pacct->ac_flag;
462 ac->ac_mem = encode_comp_t(pacct->ac_mem);
463 ac->ac_minflt = encode_comp_t(pacct->ac_minflt);
464 ac->ac_majflt = encode_comp_t(pacct->ac_majflt);
465 ac->ac_exitcode = pacct->ac_exitcode;
466 spin_unlock_irq(¤t->sighand->siglock);
467 }
468 /*
469 * do_acct_process does all actual work. Caller holds the reference to file.
470 */
do_acct_process(struct bsd_acct_struct * acct)471 static void do_acct_process(struct bsd_acct_struct *acct)
472 {
473 acct_t ac;
474 unsigned long flim;
475 const struct cred *orig_cred;
476 struct file *file = acct->file;
477
478 /*
479 * Accounting records are not subject to resource limits.
480 */
481 flim = rlimit(RLIMIT_FSIZE);
482 current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
483 /* Perform file operations on behalf of whoever enabled accounting */
484 orig_cred = override_creds(file->f_cred);
485
486 /*
487 * First check to see if there is enough free_space to continue
488 * the process accounting system.
489 */
490 if (!check_free_space(acct))
491 goto out;
492
493 fill_ac(&ac);
494 /* we really need to bite the bullet and change layout */
495 ac.ac_uid = from_kuid_munged(file->f_cred->user_ns, orig_cred->uid);
496 ac.ac_gid = from_kgid_munged(file->f_cred->user_ns, orig_cred->gid);
497 #if ACCT_VERSION == 1 || ACCT_VERSION == 2
498 /* backward-compatible 16 bit fields */
499 ac.ac_uid16 = ac.ac_uid;
500 ac.ac_gid16 = ac.ac_gid;
501 #elif ACCT_VERSION == 3
502 {
503 struct pid_namespace *ns = acct->ns;
504
505 ac.ac_pid = task_tgid_nr_ns(current, ns);
506 rcu_read_lock();
507 ac.ac_ppid = task_tgid_nr_ns(rcu_dereference(current->real_parent),
508 ns);
509 rcu_read_unlock();
510 }
511 #endif
512 /*
513 * Get freeze protection. If the fs is frozen, just skip the write
514 * as we could deadlock the system otherwise.
515 */
516 if (file_start_write_trylock(file)) {
517 /* it's been opened O_APPEND, so position is irrelevant */
518 loff_t pos = 0;
519 __kernel_write(file, &ac, sizeof(acct_t), &pos);
520 file_end_write(file);
521 }
522 out:
523 current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim;
524 revert_creds(orig_cred);
525 }
526
527 /**
528 * acct_collect - collect accounting information into pacct_struct
529 * @exitcode: task exit code
530 * @group_dead: not 0, if this thread is the last one in the process.
531 */
acct_collect(long exitcode,int group_dead)532 void acct_collect(long exitcode, int group_dead)
533 {
534 struct pacct_struct *pacct = ¤t->signal->pacct;
535 u64 utime, stime;
536 unsigned long vsize = 0;
537
538 if (group_dead && current->mm) {
539 struct vm_area_struct *vma;
540
541 mmap_read_lock(current->mm);
542 vma = current->mm->mmap;
543 while (vma) {
544 vsize += vma->vm_end - vma->vm_start;
545 vma = vma->vm_next;
546 }
547 mmap_read_unlock(current->mm);
548 }
549
550 spin_lock_irq(¤t->sighand->siglock);
551 if (group_dead)
552 pacct->ac_mem = vsize / 1024;
553 if (thread_group_leader(current)) {
554 pacct->ac_exitcode = exitcode;
555 if (current->flags & PF_FORKNOEXEC)
556 pacct->ac_flag |= AFORK;
557 }
558 if (current->flags & PF_SUPERPRIV)
559 pacct->ac_flag |= ASU;
560 if (current->flags & PF_DUMPCORE)
561 pacct->ac_flag |= ACORE;
562 if (current->flags & PF_SIGNALED)
563 pacct->ac_flag |= AXSIG;
564
565 task_cputime(current, &utime, &stime);
566 pacct->ac_utime += utime;
567 pacct->ac_stime += stime;
568 pacct->ac_minflt += current->min_flt;
569 pacct->ac_majflt += current->maj_flt;
570 spin_unlock_irq(¤t->sighand->siglock);
571 }
572
slow_acct_process(struct pid_namespace * ns)573 static void slow_acct_process(struct pid_namespace *ns)
574 {
575 for ( ; ns; ns = ns->parent) {
576 struct bsd_acct_struct *acct = acct_get(ns);
577 if (acct) {
578 do_acct_process(acct);
579 mutex_unlock(&acct->lock);
580 acct_put(acct);
581 }
582 }
583 }
584
585 /**
586 * acct_process - handles process accounting for an exiting task
587 */
acct_process(void)588 void acct_process(void)
589 {
590 struct pid_namespace *ns;
591
592 /*
593 * This loop is safe lockless, since current is still
594 * alive and holds its namespace, which in turn holds
595 * its parent.
596 */
597 for (ns = task_active_pid_ns(current); ns != NULL; ns = ns->parent) {
598 if (ns->bacct)
599 break;
600 }
601 if (unlikely(ns))
602 slow_acct_process(ns);
603 }
604
