| // 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 sys_umount(). If the accounting |
| * 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_lock 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/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 |
| */ |
| |
| static 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 */ |
| |
| #ifdef CONFIG_SYSCTL |
| static struct ctl_table kern_acct_table[] = { |
| { |
| .procname = "acct", |
| .data = &acct_parm, |
| .maxlen = 3*sizeof(int), |
| .mode = 0644, |
| .proc_handler = proc_dointvec, |
| }, |
| { } |
| }; |
| |
| static __init int kernel_acct_sysctls_init(void) |
| { |
| register_sysctl_init("kernel", kern_acct_table); |
| return 0; |
| } |
| late_initcall(kernel_acct_sysctls_init); |
| #endif /* CONFIG_SYSCTL */ |
| |
| /* |
| * 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); |
| mutex_unlock(&acct->lock); |
| pin_kill(old); |
| __mnt_drop_write(mnt); |
| mntput(mnt); |
| return 0; |
| } |
| |
| static DEFINE_MUTEX(acct_on_mutex); |
| |
| /** |
| * sys_acct - enable/disable process accounting |
| * @name: file name for accounting records or NULL to shutdown accounting |
| * |
| * sys_acct() is the only system call needed to implement process |
| * accounting. It takes the name of the file where accounting records |
| * should be written. If the filename is NULL, accounting will be |
| * shutdown. |
| * |
| * Returns: 0 for success or negative errno values for failure. |
| */ |
| SYSCALL_DEFINE1(acct, const char __user *, name) |
| { |
| int error = 0; |
| |
| if (!capable(CAP_SYS_PACCT)) |
| return -EPERM; |
| |
| if (name) { |
| struct filename *tmp = getname(name); |
| |
| if (IS_ERR(tmp)) |
| return PTR_ERR(tmp); |
| mutex_lock(&acct_on_mutex); |
| error = acct_on(tmp); |
| mutex_unlock(&acct_on_mutex); |
| putname(tmp); |
| } else { |
| rcu_read_lock(); |
| pin_kill(task_active_pid_ns(current)->bacct); |
| } |
| |
| return error; |
| } |
| |
| void acct_exit_ns(struct pid_namespace *ns) |
| { |
| rcu_read_lock(); |
| pin_kill(ns->bacct); |
| } |
| |
| /* |
| * encode an unsigned long into a comp_t |
| * |
| * This routine has been adopted from the encode_comp_t() function in |
| * the kern_acct.c file of the FreeBSD operating system. The encoding |
| * is a 13-bit fraction with a 3-bit (base 8) exponent. |
| */ |
| |
| #define MANTSIZE 13 /* 13 bit mantissa. */ |
| #define EXPSIZE 3 /* Base 8 (3 bit) exponent. */ |
| #define MAXFRACT ((1 << MANTSIZE) - 1) /* Maximum fractional value. */ |
| |
| static comp_t encode_comp_t(unsigned long value) |
| { |
| int exp, rnd; |
| |
| exp = rnd = 0; |
| while (value > MAXFRACT) { |
| rnd = value & (1 << (EXPSIZE - 1)); /* Round up? */ |
| value >>= EXPSIZE; /* Base 8 exponent == 3 bit shift. */ |
| exp++; |
| } |
| |
| /* |
| * If we need to round up, do it (and handle overflow correctly). |
| */ |
| if (rnd && (++value > MAXFRACT)) { |
| value >>= EXPSIZE; |
| exp++; |
| } |
| |
| if (exp > (((comp_t) ~0U) >> MANTSIZE)) |
| return (comp_t) ~0U; |
| /* |
| * Clean it up and polish it off. |
| */ |
| exp <<= MANTSIZE; /* Shift the exponent into place */ |
| exp += value; /* and add on the mantissa. */ |
| return exp; |
| } |
| |
| #if ACCT_VERSION == 1 || ACCT_VERSION == 2 |
| /* |
| * encode an u64 into a comp2_t (24 bits) |
| * |
| * Format: 5 bit base 2 exponent, 20 bits mantissa. |
| * The leading bit of the mantissa is not stored, but implied for |
| * non-zero exponents. |
| * Largest encodable value is 50 bits. |
| */ |
| |
| #define MANTSIZE2 20 /* 20 bit mantissa. */ |
| #define EXPSIZE2 5 /* 5 bit base 2 exponent. */ |
| #define MAXFRACT2 ((1ul << MANTSIZE2) - 1) /* Maximum fractional value. */ |
| #define MAXEXP2 ((1 << EXPSIZE2) - 1) /* Maximum exponent. */ |
| |
| static comp2_t encode_comp2_t(u64 value) |
| { |
| int exp, rnd; |
| |
| exp = (value > (MAXFRACT2>>1)); |
| rnd = 0; |
| while (value > MAXFRACT2) { |
| rnd = value & 1; |
| value >>= 1; |
| exp++; |
| } |
| |
| /* |
| * If we need to round up, do it (and handle overflow correctly). |
| */ |
| if (rnd && (++value > MAXFRACT2)) { |
| value >>= 1; |
| exp++; |
| } |
| |
| if (exp > MAXEXP2) { |
| /* Overflow. Return largest representable number instead. */ |
| return (1ul << (MANTSIZE2+EXPSIZE2-1)) - 1; |
| } else { |
| return (value & (MAXFRACT2>>1)) | (exp << (MANTSIZE2-1)); |
| } |
| } |
| #elif ACCT_VERSION == 3 |
| /* |
| * encode an u64 into a 32 bit IEEE float |
| */ |
| static u32 encode_float(u64 value) |
| { |
| unsigned exp = 190; |
| unsigned u; |
| |
| if (value == 0) |
| return 0; |
| while ((s64)value > 0) { |
| value <<= 1; |
| exp--; |
| } |
| u = (u32)(value >> 40) & 0x7fffffu; |
| return u | (exp << 23); |
| } |
| #endif |
| |
| /* |
| * Write an accounting entry for an exiting process |
| * |
| * The acct_process() call is the workhorse of the process |
| * accounting system. The struct acct is built here and then written |
| * into the accounting file. This function should only be called from |
| * do_exit() or when switching to a different output file. |
| */ |
| |
| static void fill_ac(acct_t *ac) |
| { |
| struct pacct_struct *pacct = ¤t->signal->pacct; |
| u64 elapsed, run_time; |
| time64_t btime; |
| struct tty_struct *tty; |
| |
| /* |
| * Fill the accounting struct with the needed info as recorded |
| * by the different kernel functions. |
| */ |
| memset(ac, 0, sizeof(acct_t)); |
| |
| ac->ac_version = ACCT_VERSION | ACCT_BYTEORDER; |
| strlcpy(ac->ac_comm, current->comm, sizeof(ac->ac_comm)); |
| |
| /* calculate run_time in nsec*/ |
| run_time = ktime_get_ns(); |
| run_time -= current->group_leader->start_time; |
| /* convert nsec -> AHZ */ |
| elapsed = nsec_to_AHZ(run_time); |
| #if ACCT_VERSION == 3 |
| ac->ac_etime = encode_float(elapsed); |
| #else |
| ac->ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ? |
| (unsigned long) elapsed : (unsigned long) -1l); |
| #endif |
| #if ACCT_VERSION == 1 || ACCT_VERSION == 2 |
| { |
| /* new enlarged etime field */ |
| comp2_t etime = encode_comp2_t(elapsed); |
| |
| ac->ac_etime_hi = etime >> 16; |
| ac->ac_etime_lo = (u16) etime; |
| } |
| #endif |
| do_div(elapsed, AHZ); |
| btime = ktime_get_real_seconds() - elapsed; |
| ac->ac_btime = clamp_t(time64_t, btime, 0, U32_MAX); |
| #if ACCT_VERSION==2 |
| ac->ac_ahz = AHZ; |
| #endif |
| |
| spin_lock_irq(¤t->sighand->siglock); |
| tty = current->signal->tty; /* Safe as we hold the siglock */ |
| ac->ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0; |
| ac->ac_utime = encode_comp_t(nsec_to_AHZ(pacct->ac_utime)); |
| ac->ac_stime = encode_comp_t(nsec_to_AHZ(pacct->ac_stime)); |
| ac->ac_flag = pacct->ac_flag; |
| ac->ac_mem = encode_comp_t(pacct->ac_mem); |
| ac->ac_minflt = encode_comp_t(pacct->ac_minflt); |
| ac->ac_majflt = encode_comp_t(pacct->ac_majflt); |
| ac->ac_exitcode = pacct->ac_exitcode; |
| spin_unlock_irq(¤t->sighand->siglock); |
| } |
| /* |
| * do_acct_process does all actual work. Caller holds the reference to file. |
| */ |
| static void do_acct_process(struct bsd_acct_struct *acct) |
| { |
| acct_t ac; |
| unsigned long flim; |
| const struct cred *orig_cred; |
| struct file *file = acct->file; |
| |
| /* |
| * Accounting records are not subject to resource limits. |
| */ |
| flim = rlimit(RLIMIT_FSIZE); |
| current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY; |
| /* Perform file operations on behalf of whoever enabled accounting */ |
| orig_cred = override_creds(file->f_cred); |
| |
| /* |
| * First check to see if there is enough free_space to continue |
| * the process accounting system. |
| */ |
| if (!check_free_space(acct)) |
| goto out; |
| |
| fill_ac(&ac); |
| /* we really need to bite the bullet and change layout */ |
| ac.ac_uid = from_kuid_munged(file->f_cred->user_ns, orig_cred->uid); |
| ac.ac_gid = from_kgid_munged(file->f_cred->user_ns, orig_cred->gid); |
| #if ACCT_VERSION == 1 || ACCT_VERSION == 2 |
| /* backward-compatible 16 bit fields */ |
| ac.ac_uid16 = ac.ac_uid; |
| ac.ac_gid16 = ac.ac_gid; |
| #elif ACCT_VERSION == 3 |
| { |
| struct pid_namespace *ns = acct->ns; |
| |
| ac.ac_pid = task_tgid_nr_ns(current, ns); |
| rcu_read_lock(); |
| ac.ac_ppid = task_tgid_nr_ns(rcu_dereference(current->real_parent), |
| ns); |
| rcu_read_unlock(); |
| } |
| #endif |
| /* |
| * Get freeze protection. If the fs is frozen, just skip the write |
| * as we could deadlock the system otherwise. |
| */ |
| if (file_start_write_trylock(file)) { |
| /* it's been opened O_APPEND, so position is irrelevant */ |
| loff_t pos = 0; |
| __kernel_write(file, &ac, sizeof(acct_t), &pos); |
| file_end_write(file); |
| } |
| out: |
| current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim; |
| revert_creds(orig_cred); |
| } |
| |
| /** |
| * acct_collect - collect accounting information into pacct_struct |
| * @exitcode: task exit code |
| * @group_dead: not 0, if this thread is the last one in the process. |
| */ |
| void acct_collect(long exitcode, int group_dead) |
| { |
| struct pacct_struct *pacct = ¤t->signal->pacct; |
| u64 utime, stime; |
| unsigned long vsize = 0; |
| |
| if (group_dead && current->mm) { |
| struct mm_struct *mm = current->mm; |
| VMA_ITERATOR(vmi, mm, 0); |
| struct vm_area_struct *vma; |
| |
| mmap_read_lock(mm); |
| for_each_vma(vmi, vma) |
| vsize += vma->vm_end - vma->vm_start; |
| mmap_read_unlock(mm); |
| } |
| |
| spin_lock_irq(¤t->sighand->siglock); |
| if (group_dead) |
| pacct->ac_mem = vsize / 1024; |
| if (thread_group_leader(current)) { |
| pacct->ac_exitcode = exitcode; |
| if (current->flags & PF_FORKNOEXEC) |
| pacct->ac_flag |= AFORK; |
| } |
| if (current->flags & PF_SUPERPRIV) |
| pacct->ac_flag |= ASU; |
| if (current->flags & PF_DUMPCORE) |
| pacct->ac_flag |= ACORE; |
| if (current->flags & PF_SIGNALED) |
| pacct->ac_flag |= AXSIG; |
| |
| task_cputime(current, &utime, &stime); |
| pacct->ac_utime += utime; |
| pacct->ac_stime += stime; |
| pacct->ac_minflt += current->min_flt; |
| pacct->ac_majflt += current->maj_flt; |
| spin_unlock_irq(¤t->sighand->siglock); |
| } |
| |
| static void slow_acct_process(struct pid_namespace *ns) |
| { |
| for ( ; ns; ns = ns->parent) { |
| struct bsd_acct_struct *acct = acct_get(ns); |
| if (acct) { |
| do_acct_process(acct); |
| mutex_unlock(&acct->lock); |
| acct_put(acct); |
| } |
| } |
| } |
| |
| /** |
| * acct_process - handles process accounting for an exiting task |
| */ |
| void acct_process(void) |
| { |
| struct pid_namespace *ns; |
| |
| /* |
| * This loop is safe lockless, since current is still |
| * alive and holds its namespace, which in turn holds |
| * its parent. |
| */ |
| for (ns = task_active_pid_ns(current); ns != NULL; ns = ns->parent) { |
| if (ns->bacct) |
| break; |
| } |
| if (unlikely(ns)) |
| slow_acct_process(ns); |
| } |