move IMMUTABLE|APPEND checks to notify_change()

[PATCH] move IMMUTABLE|APPEND checks to notify_change()

This patch moves lots of IMMUTABLE and APPEND flag checks scattered all around to more logical place in notify_change().

@@ -109,6 +109,9 @@ int notify_change(struct dentry * dentry

	struct timespec now;
	unsigned int ia_valid = attr->ia_valid;

+ if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
+ return -EPERM;
+

	mode = inode->i_mode;
	now = current_fs_time(inode->i_sb);

@@ -252,10 +252,6 @@ static long do_sys_truncate(const char _

	if (IS_RDONLY(inode))
		goto dput_and_out;

- error = -EPERM;
- if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
- goto dput_and_out;
-

	/*
	 * Make sure that there are no leases.
	 */
@@ -316,10 +312,6 @@ static long do_sys_ftruncate(unsigned in
	if (small && length > MAX_NON_LFS)
		goto out_putf;

- error = -EPERM;
- if (IS_APPEND(inode))
- goto out_putf;
-

	error = locks_verify_truncate(inode, file, length);
	if (!error)
		error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file);
@@ -385,10 +377,6 @@ asmlinkage long sys_utime(char __user * 
	/* 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)
@@ -398,15 +386,9 @@ asmlinkage long sys_utime(char __user * 
			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 &&
+ } else if (current->fsuid != inode->i_uid &&

		    (error = vfs_permission(&nd, MAY_WRITE)) != 0)
-			goto dput_and_out;
-	}
+		goto dput_and_out;
	mutex_lock(&inode->i_mutex);
	error = notify_change(nd.dentry, &newattrs);
	mutex_unlock(&inode->i_mutex);
@@ -442,24 +424,14 @@ long do_utimes(int dfd, char __user *fil
	/* 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;
-

		newattrs.ia_atime.tv_sec = times[0].tv_sec;
		newattrs.ia_atime.tv_nsec = times[0].tv_usec * 1000;
		newattrs.ia_mtime.tv_sec = times[1].tv_sec;
		newattrs.ia_mtime.tv_nsec = times[1].tv_usec * 1000;
		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 &&
+ } else if (current->fsuid != inode->i_uid &&

		    (error = vfs_permission(&nd, MAY_WRITE)) != 0)
-			goto dput_and_out;
-	}
+		goto dput_and_out;
	mutex_lock(&inode->i_mutex);
	error = notify_change(nd.dentry, &newattrs);
	mutex_unlock(&inode->i_mutex);
@@ -638,9 +610,6 @@ asmlinkage long sys_fchmod(unsigned int 
	err = -EROFS;
	if (IS_RDONLY(inode))
		goto out_putf;
-	err = -EPERM;
-	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
-		goto out_putf;
	mutex_lock(&inode->i_mutex);
	if (mode == (mode_t) -1)
		mode = inode->i_mode;
@@ -672,10 +641,6 @@ asmlinkage long sys_fchmodat(int dfd, co
	if (IS_RDONLY(inode))
		goto dput_and_out;

- error = -EPERM;
- if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
- goto dput_and_out;
-

	mutex_lock(&inode->i_mutex);
	if (mode == (mode_t) -1)
		mode = inode->i_mode;
@@ -709,9 +674,6 @@ static int chown_common(struct dentry * 
	error = -EROFS;
	if (IS_RDONLY(inode))
		goto out;
-	error = -EPERM;
-	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
-		goto out;
	newattrs.ia_valid =  ATTR_CTIME;
	if (user != (uid_t) -1) {
		newattrs.ia_valid |= ATTR_UID;

NAK. For example, you are allowed to do unames(file, NULL) on any file you own or can write to, whether it's append-only or not. With your change that gets -EPERM.

Do you meant utimes(file, NULL)?
But is it correct behaviour? Why then do you get -EPERM on utimes(file, smth) if the file is append-only? And why do you get -EACCESS on utimes(file, NULL), if this file is immutable?

Could you explain, why is it done so?

Thanks,
Dmitry.

RTFPOSIX...

Short version:
* immutable files are immutable, including metadata
* append-only files may be touched (when you write to the end), which
means that you can touch them. Which is what utimes(file, NULL) does.
* you can not truncate append-only file, overwrite already written
data or set timestamps to arbitrary values.

That's where the difference between utimes(file, NULL) and utimes(file, p) is - the former basically is a write-without-write ("touch foo") and the latter directly assigns to timestamps. Permissions needed for these are obviously different.

Please, read POSIX/SuS when modifying behaviour of syscalls. Really.

Al, will you ACK the patch allowing to set current times in notify_change() for APPEND files?

However, I'd like to see an explanation on dim@'s question why semantics are different and current time is allowed to be set, while arbitrary time is not.

Kirill

Does such check in notify_change() looks better for you?

notify_change():

       if (IS_IMMUTABLE(inode))
               return -EPERM;
       if (IS_APPEND(inode) &&
                       (ia_valid & ~(ATTR_CTIME | ATTR_MTIME | ATTR_ATIME)))
               return -EPERM;

Thanks,
Kirill