linux-kernel - Re: 2.6.23-rc7-mm1 - 'touch' command causes Oops.

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Message-ID: <3982.1190638701@turing-police.cc.vt.edu>
Date:	Mon, 24 Sep 2007 08:58:21 -0400
From:	Valdis.Kletnieks@...edu
To:	Christoph Hellwig <hch@...radead.org>,
	Dave Hansen <haveblue@...ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: 2.6.23-rc7-mm1 - 'touch' command causes Oops.

On Mon, 24 Sep 2007 13:05:08 BST, Christoph Hellwig said:
> On Mon, Sep 24, 2007 at 06:35:50AM -0400, Valdis.Kletnieks@...edu wrote:
> > On Mon, 24 Sep 2007 02:17:16 PDT, Andrew Morton said:
> > 
> > > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.23-rc7/2.6.23-rc7-mm1/
> > 
> > It lived fast, it died young, it didn't leave a pretty corpse...

(adding Dave Hansen to the cc: list, his patch added the mnt_want_write stuff)

> do_times passes an unitialized vfsmount into mnt_want_write.  Here's
> the quick fix (untested), but the right fix is to restructure the complete
> mess do_utimes is (never let a libc developer write your kernel code.. :)):

Close - it still blew up, as one reference to nd.mnt remained.  Fixed patch
is appended - system boots all the way with this applied.

--- linux-2.6.23-rc7-mm1/fs/utimes.c.dist	2007-09-24 05:57:38.000000000 -0400
+++ linux-2.6.23-rc7-mm1/fs/utimes.c	2007-09-24 08:48:34.000000000 -0400
@@ -59,6 +59,7 @@ long do_utimes(int dfd, char __user *fil
 	struct inode *inode;
 	struct iattr newattrs;
 	struct file *f = NULL;
+	struct vfsmount *mnt;
 
 	error = -EINVAL;
 	if (times && (!nsec_valid(times[0].tv_nsec) ||
@@ -79,17 +80,19 @@ long do_utimes(int dfd, char __user *fil
 		if (!f)
 			goto out;
 		dentry = f->f_path.dentry;
+		mnt = f->f_path.mnt;
 	} else {
 		error = __user_walk_fd(dfd, filename, (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW, &nd);
 		if (error)
 			goto out;
 
 		dentry = nd.dentry;
+		mnt = nd.mnt;
 	}
 
 	inode = dentry->d_inode;
 
-	error = mnt_want_write(nd.mnt);
+	error = mnt_want_write(mnt);
 	if (error)
 		goto dput_and_out;
 
@@ -135,7 +138,7 @@ long do_utimes(int dfd, char __user *fil
 	error = notify_change(dentry, &newattrs);
 	mutex_unlock(&inode->i_mutex);
 mnt_drop_write_and_out:
-	mnt_drop_write(nd.mnt);
+	mnt_drop_write(mnt);
 dput_and_out:
 	if (f)
 		fput(f);



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