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// SPDX-License-Identifier: GPL-2.0
/*
* linux/kernel/acct.c
*
* BSD Process Accounting for Linux
*
* Author: Marco van Wieringen <mvw@planets.elm.net>
*
* Some code based on ideas and code from:
* Thomas K. Dyas <tdyas@eden.rutgers.edu>
*
* This file implements BSD-style process accounting. Whenever any
* process exits, an accounting record of type "struct acct" is
* written to the file specified with the acct() system call. It is
* up to user-level programs to do useful things with the accounting
* log. The kernel just provides the raw accounting information.
*
* (C) Copyright 1995 - 1997 Marco van Wieringen - ELM Consultancy B.V.
*
* Plugged two leaks. 1) It didn't return acct_file into the free_filps if
* the file happened to be read-only. 2) If the accounting was suspended
* due to the lack of space it happily allowed to reopen it and completely
* lost the old acct_file. 3/10/98, Al Viro.
*
* Now we silently close acct_file on attempt to reopen. Cleaned sys_acct().
* XTerms and EMACS are manifestations of pure evil. 21/10/98, AV.
*
* Fixed a nasty interaction with with sys_umount(). If the accointing
* was suspeneded we failed to stop it on umount(). Messy.
* Another one: remount to readonly didn't stop accounting.
* Question: what should we do if we have CAP_SYS_ADMIN but not
* CAP_SYS_PACCT? Current code does the following: umount returns -EBUSY
* unless we are messing with the root. In that case we are getting a
* real mess with do_remount_sb(). 9/11/98, AV.
*
* Fixed a bunch of races (and pair of leaks). Probably not the best way,
* but this one obviously doesn't introduce deadlocks. Later. BTW, found
* one race (and leak) in BSD implementation.
* OK, that's better. ANOTHER race and leak in BSD variant. There always
* is one more bug... 10/11/98, AV.
*
* Oh, fsck... Oopsable SMP race in do_process_acct() - we must hold
* ->mmap_sem to walk the vma list of current->mm. Nasty, since it leaks
* a struct file opened for write. Fixed. 2/6/2000, AV.
*/
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/acct.h>
#include <linux/capability.h>
#include <linux/file.h>
#include <linux/tty.h>
#include <linux/security.h>
#include <linux/vfs.h>
#include <linux/jiffies.h>
#include <linux/times.h>
#include <linux/syscalls.h>
#include <linux/mount.h>
#include <linux/uaccess.h>
#include <linux/sched/cputime.h>
#include <asm/div64.h>
#include <linux/blkdev.h> /* sector_div */
#include <linux/pid_namespace.h>
#include <linux/fs_pin.h>
/*
* These constants control the amount of freespace that suspend and
* resume the process accounting system, and the time delay between
* each check.
* Turned into sysctl-controllable parameters. AV, 12/11/98
*/
int acct_parm[3] = {4, 2, 30};
#define RESUME (acct_parm[0]) /* >foo% free space - resume */
#define SUSPEND (acct_parm[1]) /* <foo% free space - suspend */
#define ACCT_TIMEOUT (acct_parm[2]) /* foo second timeout between checks */
/*
* External references and all of the globals.
*/
struct bsd_acct_struct {
struct fs_pin pin;
atomic_long_t count;
struct rcu_head rcu;
struct mutex lock;
int active;
unsigned long needcheck;
struct file *file;
struct pid_namespace *ns;
struct work_struct work;
struct completion done;
};
static void do_acct_process(struct bsd_acct_struct *acct);
/*
* Check the amount of free space and suspend/resume accordingly.
*/
static int check_free_space(struct bsd_acct_struct *acct)
{
struct kstatfs sbuf;
if (time_is_after_jiffies(acct->needcheck))
goto out;
/* May block */
if (vfs_statfs(&acct->file->f_path, &sbuf))
goto out;
if (acct->active) {
u64 suspend = sbuf.f_blocks * SUSPEND;
do_div(suspend, 100);
if (sbuf.f_bavail <= suspend) {
acct->active = 0;
pr_info("Process accounting paused\n");
}
} else {
u64 resume = sbuf.f_blocks * RESUME;
do_div(resume, 100);
if (sbuf.f_bavail >= resume) {
acct->active = 1;
pr_info("Process accounting resumed\n");
}
}
acct->needcheck = jiffies + ACCT_TIMEOUT*HZ;
out:
return acct->active;
}
static void acct_put(struct bsd_acct_struct *p)
{
if (atomic_long_dec_and_test(&p->count))
kfree_rcu(p, rcu);
}
static inline struct bsd_acct_struct *to_acct(struct fs_pin *p)
{
return p ? container_of(p, struct bsd_acct_struct, pin) : NULL;
}
static struct bsd_acct_struct *acct_get(struct pid_namespace *ns)
{
struct bsd_acct_struct *res;
again:
smp_rmb();
rcu_read_lock();
res = to_acct(READ_ONCE(ns->bacct));
if (!res) {
rcu_read_unlock();
return NULL;
}
if (!atomic_long_inc_not_zero(&res->count)) {
rcu_read_unlock();
cpu_relax();
goto again;
}
rcu_read_unlock();
mutex_lock(&res->lock);
if (res != to_acct(READ_ONCE(ns->bacct))) {
mutex_unlock(&res->lock);
acct_put(res);
goto again;
}
return res;
}
static void acct_pin_kill(struct fs_pin *pin)
{
struct bsd_acct_struct *acct = to_acct(pin);
mutex_lock(&acct->lock);
do_acct_process(acct);
schedule_work(&acct->work);
wait_for_completion(&acct->done);
cmpxchg(&acct->ns->bacct, pin, NULL);
mutex_unlock(&acct->lock);
pin_remove(pin);
acct_put(acct);
}
static void close_work(struct work_struct *work)
{
struct bsd_acct_struct *acct = container_of(work, struct bsd_acct_struct, work);
struct file *file = acct->file;
if (file->f_op->flush)
file->f_op->flush(file, NULL);
__fput_sync(file);
complete(&acct->done);
}
static int acct_on(struct filename *pathname)
{
struct file *file;
struct vfsmount *mnt, *internal;
struct pid_namespace *ns = task_active_pid_ns(current);
struct bsd_acct_struct *acct;
struct fs_pin *old;
int err;
acct = kzalloc(sizeof(struct bsd_acct_struct), GFP_KERNEL);
if (!acct)
return -ENOMEM;
/* Difference from BSD - they don't do O_APPEND */
file = file_open_name(pathname, O_WRONLY|O_APPEND|O_LARGEFILE, 0);
if (IS_ERR(file)) {
kfree(acct);
return PTR_ERR(file);
}
if (!S_ISREG(file_inode(file)->i_mode)) {
kfree(acct);
filp_close(file, NULL);
return -EACCES;
}
if (!(file->f_mode & FMODE_CAN_WRITE)) {
kfree(acct);
filp_close(file, NULL);
return -EIO;
}
internal = mnt_clone_internal(&file->f_path);
if (IS_ERR(internal)) {
kfree(acct);
filp_close(file, NULL);
return PTR_ERR(internal);
}
err = mnt_want_write(internal);
if (err) {
mntput(internal);
kfree(acct);
filp_close(file, NULL);
return err;
}
mnt = file->f_path.mnt;
file->f_path.mnt = internal;
atomic_long_set(&acct->count, 1);
init_fs_pin(&acct->pin, acct_pin_kill);
acct->file = file;
acct->needcheck = jiffies;
acct->ns = ns;
mutex_init(&acct->lock);
INIT_WORK(&acct->work, close_work);
init_completion(&acct->done);
mutex_lock_nested(&acct->lock, 1); /* nobody has seen it yet */
pin_insert(&acct->pin, mnt);
rcu_read_lock();
old = xchg(&ns->bacct, &acct->pin
|