[PATCH 1/3] lutimesat: simplify utime(2)

[PATCH 1/3] lutimesat: simplify utime(2)

[Alexey Dobriyan]

Rewrite via do_utimes() like compat_sys_utime().

Signed-off-by: Alexey Dobriyan <adobriyan@openvz.org>
---

 fs/utimes.c |   50 +++++++-------------------------------------------
 1 file changed, 7 insertions(+), 43 deletions(-)

--- a/fs/utimes.c
+++ b/fs/utimes.c
@@ -22,52 +22,16 @@ #ifdef __ARCH_WANT_SYS_UTIME
  */
 asmlinkage long sys_utime(char __user * filename, struct utimbuf __user * times)
 {
-	int error;
-	struct nameidata nd;
-	struct inode * inode;
-	struct iattr newattrs;
+	struct timeval tv[2];
 
-	error = user_path_walk(filename, &nd);
-	if (error)
-		goto out;
-	inode = nd.dentry->d_inode;
-
-	error = -EROFS;
-	if (IS_RDONLY(inode))
-		goto dput_and_out;
-
-	/* Don't worry, the checks are done in inode_change_ok() */
-	newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
 	if (times) {
-		error = -EPERM;
-		if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
-			goto dput_and_out;
-
-		error = get_user(newattrs.ia_atime.tv_sec, &times->actime);
-		newattrs.ia_atime.tv_nsec = 0;
-		if (!error)
-			error = get_user(newattrs.ia_mtime.tv_sec, &times->modtime);
-		newattrs.ia_mtime.tv_nsec = 0;
-		if (error)
-			goto dput_and_out;
-
-		newattrs.ia_valid |= ATTR_ATIME_SET | ATTR_MTIME_SET;
-	} else {
-                error = -EACCES;
-                if (IS_IMMUTABLE(inode))
-                        goto dput_and_out;
-
-		if (current->fsuid != inode->i_uid &&
-		    (error = vfs_permission(&nd, MAY_WRITE)) != 0)
-			goto dput_and_out;
+		if (get_user(tv[0].tv_sec, &times->actime) ||
+		    get_user(tv[1].tv_sec, &times->modtime))
+			return -EFAULT;
+		tv[0].tv_usec = 0;
+		tv[1].tv_usec = 0;
 	}
-	mutex_lock(&inode->i_mutex);
-	error = notify_change(nd.dentry, &newattrs);
-	mutex_unlock(&inode->i_mutex);
-dput_and_out:
-	path_release(&nd);
-out:
-	return error;
+	return do_utimes(AT_FDCWD, filename, times ? tv : NULL);
 }
 
 #endif

Re: [PATCH 1/3] lutimesat: simplify utime(2)

[Andrew Morton]

On Fri, 26 Jan 2007 14:21:42 +0300
Alexey Dobriyan <adobriyan@openvz.org> wrote:

> Rewrite via do_utimes() like compat_sys_utime().
> 
> Signed-off-by: Alexey Dobriyan <adobriyan@openvz.org>
> ---
> 
>  fs/utimes.c |   50 +++++++-------------------------------------------
>  1 file changed, 7 insertions(+), 43 deletions(-)
> 
> --- a/fs/utimes.c
> +++ b/fs/utimes.c
> @@ -22,52 +22,16 @@ #ifdef __ARCH_WANT_SYS_UTIME
>   */
>  asmlinkage long sys_utime(char __user * filename, struct utimbuf __user * times)
>  {
> -	int error;
> -	struct nameidata nd;
> -	struct inode * inode;
> -	struct iattr newattrs;
> +	struct timeval tv[2];
>  
> -	error = user_path_walk(filename, &nd);
> -	if (error)
> -		goto out;
> -	inode = nd.dentry->d_inode;
> -
> -	error = -EROFS;
> -	if (IS_RDONLY(inode))
> -		goto dput_and_out;
> -
> -	/* Don't worry, the checks are done in inode_change_ok() */
> -	newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
>  	if (times) {
> -		error = -EPERM;
> -		if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
> -			goto dput_and_out;
> -
> -		error = get_user(newattrs.ia_atime.tv_sec, &times->actime);
> -		newattrs.ia_atime.tv_nsec = 0;
> -		if (!error)
> -			error = get_user(newattrs.ia_mtime.tv_sec, &times->modtime);
> -		newattrs.ia_mtime.tv_nsec = 0;
> -		if (error)
> -			goto dput_and_out;
> -
> -		newattrs.ia_valid |= ATTR_ATIME_SET | ATTR_MTIME_SET;
> -	} else {
> -                error = -EACCES;
> -                if (IS_IMMUTABLE(inode))
> -                        goto dput_and_out;
> -
> -		if (current->fsuid != inode->i_uid &&
> -		    (error = vfs_permission(&nd, MAY_WRITE)) != 0)
> -			goto dput_and_out;
> +		if (get_user(tv[0].tv_sec, &times->actime) ||
> +		    get_user(tv[1].tv_sec, &times->modtime))
> +			return -EFAULT;
> +		tv[0].tv_usec = 0;
> +		tv[1].tv_usec = 0;
>  	}
> -	mutex_lock(&inode->i_mutex);
> -	error = notify_change(nd.dentry, &newattrs);
> -	mutex_unlock(&inode->i_mutex);
> -dput_and_out:
> -	path_release(&nd);
> -out:
> -	return error;
> +	return do_utimes(AT_FDCWD, filename, times ? tv : NULL);
>  }
>  
>  #endif

I'm somewhat surprised that this wasn't done earlier.  I wonder if there's
some subtle reason why this won't work.   How well tested is this?

Re: [PATCH 1/3] lutimesat: simplify utime(2)

[Arnd Bergmann]

On Friday 26 January 2007 21:41, Andrew Morton wrote:
> I'm somewhat surprised that this wasn't done earlier.  I wonder if there's
> some subtle reason why this won't work.   How well tested is this?

http://www.opengroup.org/onlinepubs/000095399/functions/utimes.html
lists a slight difference between utime and utimes in the handling
of EPERM/EACCESS:

> The utimes() function shall fail if:
> [EACCES] Search permission is denied by a component of the path prefix;
>  or the times argument is a null pointer and the effective user ID of the
>  process does not match the owner of the file and write access is denied.
> [EPERM] The times argument is not a null pointer and the calling process'
>  effective user ID has write access to the file but does not match the
>  owner of the file and the calling process does not have the appropriate
>  privileges.
>
> The utime() function shall fail if:
> [EACCES]  Search permission is denied by a component of the path prefix;
>  or the times argument is a null pointer and the effective user ID of the
>  process does not match the owner of the file, the process does not have
>  write permission for the file, and the process does not have appropriate
>  privileges.
> [EPERM] The times argument is not a null pointer and the calling process'
>  effective user ID does not match the owner of the file and the calling
>  process does not have the appropriate privileges.

I don't really understand how that should be implemented in different
ways, but it might be the reason that we have separate functions.

	Arnd <><

Re: [PATCH 1/3] lutimesat: simplify utime(2)

[Alexey Dobriyan]

On Sat, Jan 27, 2007 at 12:35:42AM +0100, Arnd Bergmann wrote:
> On Friday 26 January 2007 21:41, Andrew Morton wrote:
> > I'm somewhat surprised that this wasn't done earlier.  I wonder if there's
> > some subtle reason why this won't work.   How well tested is this?
> 
> http://www.opengroup.org/onlinepubs/000095399/functions/utimes.html
> lists a slight difference between utime and utimes in the handling
> of EPERM/EACCESS:
> 
> > The utimes() function shall fail if:
> > [EACCES] Search permission is denied by a component of the path prefix;
> >  or the times argument is a null pointer and the effective user ID of the
> >  process does not match the owner of the file and write access is denied.
> > [EPERM] The times argument is not a null pointer and the calling process'
> >  effective user ID has write access to the file but does not match the
> >  owner of the file and the calling process does not have the appropriate
> >  privileges.
> >
> > The utime() function shall fail if:
> > [EACCES]  Search permission is denied by a component of the path prefix;
> >  or the times argument is a null pointer and the effective user ID of the
> >  process does not match the owner of the file, the process does not have
> >  write permission for the file, and the process does not have appropriate
> >  privileges.
> > [EPERM] The times argument is not a null pointer and the calling process'
> >  effective user ID does not match the owner of the file and the calling
> >  process does not have the appropriate privileges.
> 
> I don't really understand how that should be implemented in different
> ways, but it might be the reason that we have separate functions.

Present sys_utime() and do_utimes() are identical, except the former
does direct getusering into new attributes, and the latter accept "int
dfd" instead of hardcoded current working directory.

Re: [PATCH 1/3] lutimesat: simplify utime(2)

[Alexey Dobriyan]

On Fri, Jan 26, 2007 at 12:41:20PM -0800, Andrew Morton wrote:
> On Fri, 26 Jan 2007 14:21:42 +0300
> Alexey Dobriyan <adobriyan@openvz.org> wrote:
> 
> > Rewrite via do_utimes() like compat_sys_utime().
> 
> I'm somewhat surprised that this wasn't done earlier.

Because, the following patch didn't hit -mm. :)

	From adobriyan@gmail.com Wed Oct 25 20:32:24 2006
	Date: Wed, 25 Oct 2006 20:32:24 +0400
	From: Alexey Dobriyan <adobriyan@gmail.com>
	To: Andrew Morton <akpm@osdl.org>
	Cc: linux-kernel@vger.kernel.org
	Subject: [PATCH] Shrink sys_utime()
	Message-ID: <20061025163224.GA5356@martell.zuzino.mipt.ru>
	Mime-Version: 1.0
	Content-Type: text/plain; charset=us-ascii
	Content-Disposition: inline
	User-Agent: Mutt/1.5.11
	Status: RO
	Content-Length: 3314
	Lines: 118

	All checks in sys_utime() and do_utimes() are duplicated as well as a
	comment. sys_utime() will now use do_utimes() after getting times from
	userspace and projecting them to struct timeval [2].

Nevermind.

> I wonder if there's some subtle reason why this won't work.

I don't know. Compat syscall -- I'm not touching it. Normal syscall --
time_t is long on all archs, suseconds_t is sometimes int, but we're
putting zero there.

> How well tested is this?

It passed utime tests in December's LTP.