1 files changed, 301 insertions, 326 deletions

diff --git a/kernel/acct.c b/kernel/acct.c
index 8d6e145138bb..2a2b3c874acd 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  *  linux/kernel/acct.c
  *
@@ -24,7 +25,7 @@
  *  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
+ *  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
@@ -39,26 +40,23 @@
  *  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
+ * ->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/statfs.h>
 #include <linux/jiffies.h>
-#include <linux/times.h>
 #include <linux/syscalls.h>
-#include <linux/mount.h>
-#include <asm/uaccess.h>
+#include <linux/namei.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
@@ -67,190 +65,232 @@
  * Turned into sysctl-controllable parameters. AV, 12/11/98
  */
 
-int acct_parm[3] = {4, 2, 30};
+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 const 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.
  */
-static void do_acct_process(struct bsd_acct_struct *acct,
-		struct pid_namespace *ns, struct file *);
 
-/*
- * This structure is used so that all the data protected by lock
- * can be placed in the same cache line as the lock.  This primes
- * the cache line to have the data after getting the lock.
- */
 struct bsd_acct_struct {
-	int			active;
+	struct fs_pin		pin;
+	atomic_long_t		count;
+	struct rcu_head		rcu;
+	struct mutex		lock;
+	bool			active;
+	bool			check_space;
 	unsigned long		needcheck;
 	struct file		*file;
 	struct pid_namespace	*ns;
-	struct list_head	list;
+	struct work_struct	work;
+	struct completion	done;
+	acct_t			ac;
 };
 
-static DEFINE_SPINLOCK(acct_lock);
-static LIST_HEAD(acct_list);
+static void fill_ac(struct bsd_acct_struct *acct);
+static void acct_write_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 file *file)
+static bool check_free_space(struct bsd_acct_struct *acct)
 {
 	struct kstatfs sbuf;
-	int res;
-	int act;
-	u64 resume;
-	u64 suspend;
 
-	spin_lock(&acct_lock);
-	res = acct->active;
-	if (!file || time_is_before_jiffies(acct->needcheck))
-		goto out;
-	spin_unlock(&acct_lock);
+	if (!acct->check_space)
+		return acct->active;
 
 	/* May block */
-	if (vfs_statfs(&file->f_path, &sbuf))
-		return res;
-	suspend = sbuf.f_blocks * SUSPEND;
-	resume = sbuf.f_blocks * RESUME;
-
-	do_div(suspend, 100);
-	do_div(resume, 100);
-
-	if (sbuf.f_bavail <= suspend)
-		act = -1;
-	else if (sbuf.f_bavail >= resume)
-		act = 1;
-	else
-		act = 0;
-
-	/*
-	 * If some joker switched acct->file under us we'ld better be
-	 * silent and _not_ touch anything.
-	 */
-	spin_lock(&acct_lock);
-	if (file != acct->file) {
-		if (act)
-			res = act>0;
-		goto out;
-	}
+	if (vfs_statfs(&acct->file->f_path, &sbuf))
+		return acct->active;
 
 	if (acct->active) {
-		if (act < 0) {
-			acct->active = 0;
-			printk(KERN_INFO "Process accounting paused\n");
+		u64 suspend = sbuf.f_blocks * SUSPEND;
+		do_div(suspend, 100);
+		if (sbuf.f_bavail <= suspend) {
+			acct->active = false;
+			pr_info("Process accounting paused\n");
 		}
 	} else {
-		if (act > 0) {
-			acct->active = 1;
-			printk(KERN_INFO "Process accounting resumed\n");
+		u64 resume = sbuf.f_blocks * RESUME;
+		do_div(resume, 100);
+		if (sbuf.f_bavail >= resume) {
+			acct->active = true;
+			pr_info("Process accounting resumed\n");
 		}
 	}
 
 	acct->needcheck = jiffies + ACCT_TIMEOUT*HZ;
-	res = acct->active;
-out:
-	spin_unlock(&acct_lock);
-	return res;
+	return acct->active;
 }
 
-/*
- * Close the old accounting file (if currently open) and then replace
- * it with file (if non-NULL).
- *
- * NOTE: acct_lock MUST be held on entry and exit.
- */
-static void acct_file_reopen(struct bsd_acct_struct *acct, struct file *file,
-		struct pid_namespace *ns)
+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 file *old_acct = NULL;
-	struct pid_namespace *old_ns = NULL;
-
-	if (acct->file) {
-		old_acct = acct->file;
-		old_ns = acct->ns;
-		acct->active = 0;
-		acct->file = NULL;
-		acct->ns = NULL;
-		list_del(&acct->list);
+	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 (file) {
-		acct->file = file;
-		acct->ns = ns;
-		acct->needcheck = jiffies + ACCT_TIMEOUT*HZ;
-		acct->active = 1;
-		list_add(&acct->list, &acct_list);
+	if (!atomic_long_inc_not_zero(&res->count)) {
+		rcu_read_unlock();
+		cpu_relax();
+		goto again;
 	}
-	if (old_acct) {
-		mnt_unpin(old_acct->f_path.mnt);
-		spin_unlock(&acct_lock);
-		do_acct_process(acct, old_ns, old_acct);
-		filp_close(old_acct, NULL);
-		spin_lock(&acct_lock);
+	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 int acct_on(struct filename *pathname)
+static void acct_pin_kill(struct fs_pin *pin)
 {
-	struct file *file;
-	struct vfsmount *mnt;
-	struct pid_namespace *ns;
-	struct bsd_acct_struct *acct = NULL;
+	struct bsd_acct_struct *acct = to_acct(pin);
+	mutex_lock(&acct->lock);
+	/*
+	 * Fill the accounting struct with the exiting task's info
+	 * before punting to the workqueue.
+	 */
+	fill_ac(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;
+
+	/* We were fired by acct_pin_kill() which holds acct->lock. */
+	acct_write_process(acct);
+	if (file->f_op->flush)
+		file->f_op->flush(file, NULL);
+	__fput_sync(file);
+	complete(&acct->done);
+}
+
+DEFINE_FREE(fput_sync, struct file *, if (!IS_ERR_OR_NULL(_T)) __fput_sync(_T))
+static int acct_on(const char __user *name)
+{
 	/* Difference from BSD - they don't do O_APPEND */
-	file = file_open_name(pathname, O_WRONLY|O_APPEND|O_LARGEFILE, 0);
+	const int open_flags = O_WRONLY|O_APPEND|O_LARGEFILE;
+	struct pid_namespace *ns = task_active_pid_ns(current);
+	struct filename *pathname __free(putname) = getname(name);
+	struct file *original_file __free(fput) = NULL;	// in that order
+	struct path internal __free(path_put) = {};	// in that order
+	struct file *file __free(fput_sync) = NULL;	// in that order
+	struct bsd_acct_struct *acct;
+	struct vfsmount *mnt;
+	struct fs_pin *old;
+
+	if (IS_ERR(pathname))
+		return PTR_ERR(pathname);
+	original_file = file_open_name(pathname, open_flags, 0);
+	if (IS_ERR(original_file))
+		return PTR_ERR(original_file);
+
+	mnt = mnt_clone_internal(&original_file->f_path);
+	if (IS_ERR(mnt))
+		return PTR_ERR(mnt);
+
+	internal.mnt = mnt;
+	internal.dentry = dget(mnt->mnt_root);
+
+	file = dentry_open(&internal, open_flags, current_cred());
 	if (IS_ERR(file))
 		return PTR_ERR(file);
 
-	if (!S_ISREG(file_inode(file)->i_mode)) {
-		filp_close(file, NULL);
+	if (!S_ISREG(file_inode(file)->i_mode))
 		return -EACCES;
-	}
-
-	if (!file->f_op->write) {
-		filp_close(file, NULL);
-		return -EIO;
-	}
 
-	ns = task_active_pid_ns(current);
-	if (ns->bacct == NULL) {
-		acct = kzalloc(sizeof(struct bsd_acct_struct), GFP_KERNEL);
-		if (acct == NULL) {
-			filp_close(file, NULL);
-			return -ENOMEM;
-		}
-	}
+	/* Exclude kernel kernel internal filesystems. */
+	if (file_inode(file)->i_sb->s_flags & (SB_NOUSER | SB_KERNMOUNT))
+		return -EINVAL;
 
-	spin_lock(&acct_lock);
-	if (ns->bacct == NULL) {
-		ns->bacct = acct;
-		acct = NULL;
-	}
+	/* Exclude procfs and sysfs. */
+	if (file_inode(file)->i_sb->s_iflags & SB_I_USERNS_VISIBLE)
+		return -EINVAL;
 
-	mnt = file->f_path.mnt;
-	mnt_pin(mnt);
-	acct_file_reopen(ns->bacct, file, ns);
-	spin_unlock(&acct_lock);
+	if (!(file->f_mode & FMODE_CAN_WRITE))
+		return -EIO;
 
-	mntput(mnt); /* it's pinned, now give up active reference */
-	kfree(acct);
+	acct = kzalloc(sizeof(struct bsd_acct_struct), GFP_KERNEL);
+	if (!acct)
+		return -ENOMEM;
+
+	atomic_long_set(&acct->count, 1);
+	init_fs_pin(&acct->pin, acct_pin_kill);
+	acct->file = no_free_ptr(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, original_file->f_path.mnt);
 
+	rcu_read_lock();
+	old = xchg(&ns->bacct, &acct->pin);
+	mutex_unlock(&acct->lock);
+	pin_kill(old);
 	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
  *
- * Returns 0 for success or negative errno values for failure.
- *
  * 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)
 {
@@ -260,85 +300,25 @@ SYSCALL_DEFINE1(acct, const char __user *, name)
 		return -EPERM;
 
 	if (name) {
-		struct filename *tmp = getname(name);
-		if (IS_ERR(tmp))
-			return (PTR_ERR(tmp));
-		error = acct_on(tmp);
-		putname(tmp);
+		mutex_lock(&acct_on_mutex);
+		error = acct_on(name);
+		mutex_unlock(&acct_on_mutex);
 	} else {
-		struct bsd_acct_struct *acct;
-
-		acct = task_active_pid_ns(current)->bacct;
-		if (acct == NULL)
-			return 0;
-
-		spin_lock(&acct_lock);
-		acct_file_reopen(acct, NULL, NULL);
-		spin_unlock(&acct_lock);
+		rcu_read_lock();
+		pin_kill(task_active_pid_ns(current)->bacct);
 	}
 
 	return error;
 }
 
-/**
- * acct_auto_close - turn off a filesystem's accounting if it is on
- * @m: vfsmount being shut down
- *
- * If the accounting is turned on for a file in the subtree pointed to
- * to by m, turn accounting off.  Done when m is about to die.
- */
-void acct_auto_close_mnt(struct vfsmount *m)
-{
-	struct bsd_acct_struct *acct;
-
-	spin_lock(&acct_lock);
-restart:
-	list_for_each_entry(acct, &acct_list, list)
-		if (acct->file && acct->file->f_path.mnt == m) {
-			acct_file_reopen(acct, NULL, NULL);
-			goto restart;
-		}
-	spin_unlock(&acct_lock);
-}
-
-/**
- * acct_auto_close - turn off a filesystem's accounting if it is on
- * @sb: super block for the filesystem
- *
- * If the accounting is turned on for a file in the filesystem pointed
- * to by sb, turn accounting off.
- */
-void acct_auto_close(struct super_block *sb)
-{
-	struct bsd_acct_struct *acct;
-
-	spin_lock(&acct_lock);
-restart:
-	list_for_each_entry(acct, &acct_list, list)
-		if (acct->file && acct->file->f_path.dentry->d_sb == sb) {
-			acct_file_reopen(acct, NULL, NULL);
-			goto restart;
-		}
-	spin_unlock(&acct_lock);
-}
-
 void acct_exit_ns(struct pid_namespace *ns)
 {
-	struct bsd_acct_struct *acct = ns->bacct;
-
-	if (acct == NULL)
-		return;
-
-	spin_lock(&acct_lock);
-	if (acct->file != NULL)
-		acct_file_reopen(acct, NULL, NULL);
-	spin_unlock(&acct_lock);
-
-	kfree(acct);
+	rcu_read_lock();
+	pin_kill(ns->bacct);
 }
 
 /*
- *  encode an unsigned long into a comp_t
+ *  encode an u64 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
@@ -349,7 +329,7 @@ void acct_exit_ns(struct pid_namespace *ns)
 #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)
+static comp_t encode_comp_t(u64 value)
 {
 	int exp, rnd;
 
@@ -368,6 +348,8 @@ static comp_t encode_comp_t(unsigned long value)
 		exp++;
 	}
 
+	if (exp > (((comp_t) ~0U) >> MANTSIZE))
+		return (comp_t) ~0U;
 	/*
 	 * Clean it up and polish it off.
 	 */
@@ -376,7 +358,7 @@ static comp_t encode_comp_t(unsigned long value)
 	return exp;
 }
 
-#if ACCT_VERSION==1 || ACCT_VERSION==2
+#if ACCT_VERSION == 1 || ACCT_VERSION == 2
 /*
  * encode an u64 into a comp2_t (24 bits)
  *
@@ -389,7 +371,7 @@ static comp_t encode_comp_t(unsigned long value)
 #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. */
+#define MAXEXP2         ((1 << EXPSIZE2) - 1)    /* Maximum exponent. */
 
 static comp2_t encode_comp2_t(u64 value)
 {
@@ -418,9 +400,7 @@ static comp2_t encode_comp2_t(u64 value)
 		return (value & (MAXFRACT2>>1)) | (exp << (MANTSIZE2-1));
 	}
 }
-#endif
-
-#if ACCT_VERSION==3
+#elif ACCT_VERSION == 3
 /*
  * encode an u64 into a 32 bit IEEE float
  */
@@ -429,8 +409,9 @@ static u32 encode_float(u64 value)
 	unsigned exp = 190;
 	unsigned u;
 
-	if (value==0) return 0;
-	while ((s64)value > 0){
+	if (value == 0)
+		return 0;
+	while ((s64)value > 0) {
 		value <<= 1;
 		exp--;
 	}
@@ -448,121 +429,126 @@ static u32 encode_float(u64 value)
  *  do_exit() or when switching to a different output file.
  */
 
-/*
- *  do_acct_process does all actual work. Caller holds the reference to file.
- */
-static void do_acct_process(struct bsd_acct_struct *acct,
-		struct pid_namespace *ns, struct file *file)
+static void fill_ac(struct bsd_acct_struct *acct)
 {
 	struct pacct_struct *pacct = &current->signal->pacct;
-	acct_t ac;
-	mm_segment_t fs;
-	unsigned long flim;
-	u64 elapsed;
-	u64 run_time;
-	struct timespec uptime;
+	struct file *file = acct->file;
+	acct_t *ac = &acct->ac;
+	u64 elapsed, run_time;
+	time64_t btime;
 	struct tty_struct *tty;
-	const struct cred *orig_cred;
 
-	/* Perform file operations on behalf of whoever enabled accounting */
-	orig_cred = override_creds(file->f_cred);
+	lockdep_assert_held(&acct->lock);
 
-	/*
-	 * First check to see if there is enough free_space to continue
-	 * the process accounting system.
-	 */
-	if (!check_free_space(acct, file))
-		goto out;
+	if (time_is_after_jiffies(acct->needcheck)) {
+		acct->check_space = false;
+
+		/* Don't fill in @ac if nothing will be written. */
+		if (!acct->active)
+			return;
+	} else {
+		acct->check_space = true;
+	}
 
 	/*
 	 * Fill the accounting struct with the needed info as recorded
 	 * by the different kernel functions.
 	 */
-	memset(&ac, 0, sizeof(acct_t));
+	memset(ac, 0, sizeof(acct_t));
 
-	ac.ac_version = ACCT_VERSION | ACCT_BYTEORDER;
-	strlcpy(ac.ac_comm, current->comm, sizeof(ac.ac_comm));
+	ac->ac_version = ACCT_VERSION | ACCT_BYTEORDER;
+	strscpy(ac->ac_comm, current->comm, sizeof(ac->ac_comm));
 
 	/* calculate run_time in nsec*/
-	do_posix_clock_monotonic_gettime(&uptime);
-	run_time = (u64)uptime.tv_sec*NSEC_PER_SEC + uptime.tv_nsec;
-	run_time -= (u64)current->group_leader->start_time.tv_sec * NSEC_PER_SEC
-		       + current->group_leader->start_time.tv_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);
+#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);
+	ac->ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ?
+				(unsigned long) elapsed : (unsigned long) -1l);
 #endif
-#if ACCT_VERSION==1 || ACCT_VERSION==2
+#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;
+
+		ac->ac_etime_hi = etime >> 16;
+		ac->ac_etime_lo = (u16) etime;
 	}
 #endif
 	do_div(elapsed, AHZ);
-	ac.ac_btime = get_seconds() - elapsed;
-	/* 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==2
-	ac.ac_ahz = AHZ;
-#endif
-#if ACCT_VERSION==1 || ACCT_VERSION==2
-	/* backward-compatible 16 bit fields */
-	ac.ac_uid16 = ac.ac_uid;
-	ac.ac_gid16 = ac.ac_gid;
-#endif
-#if ACCT_VERSION==3
-	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();
+	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(&current->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(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_utime)));
-	ac.ac_stime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(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;
+	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(&current->sighand->siglock);
-	ac.ac_io = encode_comp_t(0 /* current->io_usage */);	/* %% */
-	ac.ac_rw = encode_comp_t(ac.ac_io / 1024);
-	ac.ac_swaps = encode_comp_t(0);
 
-	/*
-	 * 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))
-		goto out;
-	/*
-	 * Kernel segment override to datasegment and write it
-	 * to the accounting file.
-	 */
-	fs = get_fs();
-	set_fs(KERNEL_DS);
-	/*
-	 * Accounting records are not subject to resource limits.
-	 */
-	flim = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
+	/* we really need to bite the bullet and change layout */
+	ac->ac_uid = from_kuid_munged(file->f_cred->user_ns, current_uid());
+	ac->ac_gid = from_kgid_munged(file->f_cred->user_ns, current_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
+}
+
+static void acct_write_process(struct bsd_acct_struct *acct)
+{
+	struct file *file = acct->file;
+	acct_t *ac = &acct->ac;
+
+	/* Perform file operations on behalf of whoever enabled accounting */
+	scoped_with_creds(file->f_cred) {
+		/*
+		 * First check to see if there is enough free_space to continue
+		 * the process accounting system. Then get freeze protection. If
+		 * the fs is frozen, just skip the write as we could deadlock
+		 * the system otherwise.
+		 */
+		if (check_free_space(acct) && 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);
+		}
+	}
+}
+
+static void do_acct_process(struct bsd_acct_struct *acct)
+{
+	unsigned long flim;
+
+	/* Accounting records are not subject to resource limits. */
+	flim = rlimit(RLIMIT_FSIZE);
 	current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
-	file->f_op->write(file, (char *)&ac,
-			       sizeof(acct_t), &file->f_pos);
+	fill_ac(acct);
+	acct_write_process(acct);
 	current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim;
-	set_fs(fs);
-	file_end_write(file);
-out:
-	revert_creds(orig_cred);
 }
 
 /**
@@ -573,18 +559,18 @@ out:
 void acct_collect(long exitcode, int group_dead)
 {
 	struct pacct_struct *pacct = &current->signal->pacct;
-	cputime_t utime, stime;
+	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;
-		down_read(&current->mm->mmap_sem);
-		vma = current->mm->mmap;
-		while (vma) {
+
+		mmap_read_lock(mm);
+		for_each_vma(vmi, vma)
 			vsize += vma->vm_end - vma->vm_start;
-			vma = vma->vm_next;
-		}
-		up_read(&current->mm->mmap_sem);
+		mmap_read_unlock(mm);
 	}
 
 	spin_lock_irq(&current->sighand->siglock);
@@ -601,6 +587,7 @@ void acct_collect(long exitcode, int group_dead)
 		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;
@@ -609,36 +596,20 @@ void acct_collect(long exitcode, int group_dead)
 	spin_unlock_irq(&current->sighand->siglock);
 }
 
-static void acct_process_in_ns(struct pid_namespace *ns)
+static void slow_acct_process(struct pid_namespace *ns)
 {
-	struct file *file = NULL;
-	struct bsd_acct_struct *acct;
-
-	acct = ns->bacct;
-	/*
-	 * accelerate the common fastpath:
-	 */
-	if (!acct || !acct->file)
-		return;
-
-	spin_lock(&acct_lock);
-	file = acct->file;
-	if (unlikely(!file)) {
-		spin_unlock(&acct_lock);
-		return;
+	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);
+		}
 	}
-	get_file(file);
-	spin_unlock(&acct_lock);
-
-	do_acct_process(acct, ns, file);
-	fput(file);
 }
 
 /**
- * acct_process - now just a wrapper around acct_process_in_ns,
- * which in turn is a wrapper around do_acct_process.
- *
- * handles process accounting for an exiting task
+ * acct_process - handles process accounting for an exiting task
  */
 void acct_process(void)
 {
@@ -649,6 +620,10 @@ void acct_process(void)
 	 * alive and holds its namespace, which in turn holds
 	 * its parent.
 	 */
-	for (ns = task_active_pid_ns(current); ns != NULL; ns = ns->parent)
-		acct_process_in_ns(ns);
+	for (ns = task_active_pid_ns(current); ns != NULL; ns = ns->parent) {
+		if (ns->bacct)
+			break;
+	}
+	if (unlikely(ns))
+		slow_acct_process(ns);
 }