linux-kernel - Re: [parch 3/4] vfs: utimensat(): fix error checking for {UTIME_NOW,UTIME

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Message-Id: <E1K3lIS-0007lg-4e@pomaz-ex.szeredi.hu>
Date:	Wed, 04 Jun 2008 07:12:28 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	mtk.manpages@...glemail.com
CC:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	hch@....de, miklos@...redi.hu, viro@...iv.linux.org.uk,
	jamie@...reable.org, drepper@...hat.com,
	linux-fsdevel@...r.kernel.org, subrata@...ux.vnet.ibm.com
Subject: Re: [parch 3/4] vfs: utimensat(): fix error checking for {UTIME_NOW,UTIME_OMIT}
 case

> > Miklos suggested an alternative idea, migrating the
> > is_owner_or_cap() checks into fs/attr.c:inode_change_ok() via
> > the use of an ATTR_OWNER_CHECK flag.  Maybe we could do that
> > later, but for now I've gone with this version, which is
> > simpler, and can be more easily read as being correct.
> 
> Wise decision.

Or maybe not.  Isn't this a simpler and more readable patch?

Index: linux/fs/attr.c
===================================================================
--- linux.orig/fs/attr.c	2008-06-03 13:10:11.000000000 +0200
+++ linux/fs/attr.c	2008-06-04 07:07:23.000000000 +0200
@@ -51,7 +51,7 @@ int inode_change_ok(struct inode *inode,
 	}
 
 	/* Check for setting the inode time. */
-	if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET)) {
+	if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_UPDATE_TIMES)) {
 		if (!is_owner_or_cap(inode))
 			goto error;
 	}
Index: linux/fs/utimes.c
===================================================================
--- linux.orig/fs/utimes.c	2008-06-03 13:10:11.000000000 +0200
+++ linux/fs/utimes.c	2008-06-04 07:10:53.000000000 +0200
@@ -102,9 +102,14 @@ long do_utimes(int dfd, char __user *fil
 	if (error)
 		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) {
+		/*
+		 * Checking the owner is done in inode_change_ok(),
+		 * even for the special UTIME_OMIT/UTIME_NOW cases.
+		 */
+		newattrs.ia_valid |= ATTR_UPDATE_TIMES
+
 		error = -EPERM;
                 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
 			goto mnt_drop_write_and_out;
Index: linux/include/linux/fs.h
===================================================================
--- linux.orig/include/linux/fs.h	2008-06-03 13:10:25.000000000 +0200
+++ linux/include/linux/fs.h	2008-06-04 07:07:43.000000000 +0200
@@ -333,6 +333,7 @@ typedef void (dio_iodone_t)(struct kiocb
 #define ATTR_FILE	8192
 #define ATTR_KILL_PRIV	16384
 #define ATTR_OPEN	32768	/* Truncating from open(O_TRUNC) */
+#define ATTR_UPDATE_TIMES	(1 << 16)
 
 /*
  * This is the Inode Attributes structure, used for notify_change().  It
--
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