utimes.c 7.15 KB
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// SPDX-License-Identifier: GPL-2.0
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#include <linux/file.h>
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#include <linux/mount.h>
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#include <linux/namei.h>
#include <linux/utime.h>
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#include <linux/syscalls.h>
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#include <linux/uaccess.h>
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#include <linux/compat.h>
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#include <asm/unistd.h>

#ifdef __ARCH_WANT_SYS_UTIME

/*
 * sys_utime() can be implemented in user-level using sys_utimes().
 * Is this for backwards compatibility?  If so, why not move it
 * into the appropriate arch directory (for those architectures that
 * need it).
 */

/* If times==NULL, set access and modification to current time,
 * must be owner or have write permission.
 * Else, update from *times, must be owner or super user.
 */
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SYSCALL_DEFINE2(utime, char __user *, filename, struct utimbuf __user *, times)
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{
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	struct timespec64 tv[2];
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	if (times) {
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		if (get_user(tv[0].tv_sec, &times->actime) ||
		    get_user(tv[1].tv_sec, &times->modtime))
			return -EFAULT;
		tv[0].tv_nsec = 0;
		tv[1].tv_nsec = 0;
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	}
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	return do_utimes(AT_FDCWD, filename, times ? tv : NULL, 0);
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}

#endif

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static bool nsec_valid(long nsec)
{
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	if (nsec == UTIME_OMIT || nsec == UTIME_NOW)
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		return true;

	return nsec >= 0 && nsec <= 999999999;
}

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static int utimes_common(const struct path *path, struct timespec64 *times)
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{
	int error;
	struct iattr newattrs;
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	struct inode *inode = path->dentry->d_inode;
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	struct inode *delegated_inode = NULL;
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	error = mnt_want_write(path->mnt);
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	if (error)
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		goto out;
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	if (times && times[0].tv_nsec == UTIME_NOW &&
		     times[1].tv_nsec == UTIME_NOW)
		times = NULL;

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	newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
	if (times) {
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		if (times[0].tv_nsec == UTIME_OMIT)
			newattrs.ia_valid &= ~ATTR_ATIME;
		else if (times[0].tv_nsec != UTIME_NOW) {
			newattrs.ia_atime.tv_sec = times[0].tv_sec;
			newattrs.ia_atime.tv_nsec = times[0].tv_nsec;
			newattrs.ia_valid |= ATTR_ATIME_SET;
		}

		if (times[1].tv_nsec == UTIME_OMIT)
			newattrs.ia_valid &= ~ATTR_MTIME;
		else if (times[1].tv_nsec != UTIME_NOW) {
			newattrs.ia_mtime.tv_sec = times[1].tv_sec;
			newattrs.ia_mtime.tv_nsec = times[1].tv_nsec;
			newattrs.ia_valid |= ATTR_MTIME_SET;
		}
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		/*
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		 * Tell setattr_prepare(), that this is an explicit time
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		 * update, even if neither ATTR_ATIME_SET nor ATTR_MTIME_SET
		 * were used.
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		 */
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		newattrs.ia_valid |= ATTR_TIMES_SET;
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	} else {
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		newattrs.ia_valid |= ATTR_TOUCH;
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	}
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retry_deleg:
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	inode_lock(inode);
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	error = notify_change(path->dentry, &newattrs, &delegated_inode);
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	inode_unlock(inode);
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	if (delegated_inode) {
		error = break_deleg_wait(&delegated_inode);
		if (!error)
			goto retry_deleg;
	}
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	mnt_drop_write(path->mnt);
out:
	return error;
}

/*
 * do_utimes - change times on filename or file descriptor
 * @dfd: open file descriptor, -1 or AT_FDCWD
 * @filename: path name or NULL
 * @times: new times or NULL
 * @flags: zero or more flags (only AT_SYMLINK_NOFOLLOW for the moment)
 *
 * If filename is NULL and dfd refers to an open file, then operate on
 * the file.  Otherwise look up filename, possibly using dfd as a
 * starting point.
 *
 * If times==NULL, set access and modification to current time,
 * must be owner or have write permission.
 * Else, update from *times, must be owner or super user.
 */
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long do_utimes(int dfd, const char __user *filename, struct timespec64 *times,
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	       int flags)
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{
	int error = -EINVAL;

	if (times && (!nsec_valid(times[0].tv_nsec) ||
		      !nsec_valid(times[1].tv_nsec))) {
		goto out;
	}

	if (flags & ~AT_SYMLINK_NOFOLLOW)
		goto out;

	if (filename == NULL && dfd != AT_FDCWD) {
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		struct fd f;
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		if (flags & AT_SYMLINK_NOFOLLOW)
			goto out;

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		f = fdget(dfd);
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		error = -EBADF;
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		if (!f.file)
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			goto out;

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		error = utimes_common(&f.file->f_path, times);
		fdput(f);
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	} else {
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		struct path path;
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		int lookup_flags = 0;

		if (!(flags & AT_SYMLINK_NOFOLLOW))
			lookup_flags |= LOOKUP_FOLLOW;
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retry:
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		error = user_path_at(dfd, filename, lookup_flags, &path);
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		if (error)
			goto out;

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		error = utimes_common(&path, times);
		path_put(&path);
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		if (retry_estale(error, lookup_flags)) {
			lookup_flags |= LOOKUP_REVAL;
			goto retry;
		}
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	}

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out:
	return error;
}

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SYSCALL_DEFINE4(utimensat, int, dfd, const char __user *, filename,
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		struct timespec __user *, utimes, int, flags)
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{
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	struct timespec64 tstimes[2];
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	if (utimes) {
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		if ((get_timespec64(&tstimes[0], &utimes[0]) ||
			get_timespec64(&tstimes[1], &utimes[1])))
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			return -EFAULT;

		/* Nothing to do, we must not even check the path.  */
		if (tstimes[0].tv_nsec == UTIME_OMIT &&
		    tstimes[1].tv_nsec == UTIME_OMIT)
			return 0;
	}

	return do_utimes(dfd, filename, utimes ? tstimes : NULL, flags);
}

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SYSCALL_DEFINE3(futimesat, int, dfd, const char __user *, filename,
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		struct timeval __user *, utimes)
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{
	struct timeval times[2];
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	struct timespec64 tstimes[2];
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	if (utimes) {
		if (copy_from_user(&times, utimes, sizeof(times)))
			return -EFAULT;

		/* This test is needed to catch all invalid values.  If we
		   would test only in do_utimes we would miss those invalid
		   values truncated by the multiplication with 1000.  Note
		   that we also catch UTIME_{NOW,OMIT} here which are only
		   valid for utimensat.  */
		if (times[0].tv_usec >= 1000000 || times[0].tv_usec < 0 ||
		    times[1].tv_usec >= 1000000 || times[1].tv_usec < 0)
			return -EINVAL;

		tstimes[0].tv_sec = times[0].tv_sec;
		tstimes[0].tv_nsec = 1000 * times[0].tv_usec;
		tstimes[1].tv_sec = times[1].tv_sec;
		tstimes[1].tv_nsec = 1000 * times[1].tv_usec;
	}
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	return do_utimes(dfd, filename, utimes ? tstimes : NULL, 0);
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}

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SYSCALL_DEFINE2(utimes, char __user *, filename,
		struct timeval __user *, utimes)
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{
	return sys_futimesat(AT_FDCWD, filename, utimes);
}
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#ifdef CONFIG_COMPAT
/*
 * Not all architectures have sys_utime, so implement this in terms
 * of sys_utimes.
 */
COMPAT_SYSCALL_DEFINE2(utime, const char __user *, filename,
		       struct compat_utimbuf __user *, t)
{
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	struct timespec64 tv[2];
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	if (t) {
		if (get_user(tv[0].tv_sec, &t->actime) ||
		    get_user(tv[1].tv_sec, &t->modtime))
			return -EFAULT;
		tv[0].tv_nsec = 0;
		tv[1].tv_nsec = 0;
	}
	return do_utimes(AT_FDCWD, filename, t ? tv : NULL, 0);
}

COMPAT_SYSCALL_DEFINE4(utimensat, unsigned int, dfd, const char __user *, filename, struct compat_timespec __user *, t, int, flags)
{
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	struct timespec64 tv[2];
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	if  (t) {
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		if (compat_get_timespec64(&tv[0], &t[0]) ||
		    compat_get_timespec64(&tv[1], &t[1]))
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			return -EFAULT;

		if (tv[0].tv_nsec == UTIME_OMIT && tv[1].tv_nsec == UTIME_OMIT)
			return 0;
	}
	return do_utimes(dfd, filename, t ? tv : NULL, flags);
}

COMPAT_SYSCALL_DEFINE3(futimesat, unsigned int, dfd, const char __user *, filename, struct compat_timeval __user *, t)
{
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	struct timespec64 tv[2];
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	if (t) {
		if (get_user(tv[0].tv_sec, &t[0].tv_sec) ||
		    get_user(tv[0].tv_nsec, &t[0].tv_usec) ||
		    get_user(tv[1].tv_sec, &t[1].tv_sec) ||
		    get_user(tv[1].tv_nsec, &t[1].tv_usec))
			return -EFAULT;
		if (tv[0].tv_nsec >= 1000000 || tv[0].tv_nsec < 0 ||
		    tv[1].tv_nsec >= 1000000 || tv[1].tv_nsec < 0)
			return -EINVAL;
		tv[0].tv_nsec *= 1000;
		tv[1].tv_nsec *= 1000;
	}
	return do_utimes(dfd, filename, t ? tv : NULL, 0);
}

COMPAT_SYSCALL_DEFINE2(utimes, const char __user *, filename, struct compat_timeval __user *, t)
{
	return compat_sys_futimesat(AT_FDCWD, filename, t);
}
#endif