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From: Grant Coady <gcoady.lk@gmail.com>
To: Willy Tarreau <w@1wt.eu>
Cc: Marcelo Tosatti <marcelo@kvack.org>, linux-kernel@vger.kernel.org,
       Al Viro <viro@ftp.linux.org.uk>
Subject: Re: Linux 2.4.33-rc1
Date: Mon, 19 Jun 2006 09:07:03 +1000
Organization: http://bugsplatter.mine.nu/
Reply-To: Grant Coady <gcoady.lk@gmail.com>
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References: <20060616181419.GA15734@dmt> <hka6925bl0in1f3jm7m4vh975a64lcbi7g@4ax.com> <20060618133718.GA2467@dmt> <ksib9210010mt9r3gjevi3dhlp4biqf59k@4ax.com> <20060618223736.GA4965@1wt.eu>
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On Mon, 19 Jun 2006 00:37:36 +0200, Willy Tarreau <w@1wt.eu> wrote:

>Hi Grant,
>
>On Mon, Jun 19, 2006 at 08:25:06AM +1000, Grant Coady wrote:
>> On Sun, 18 Jun 2006 10:37:18 -0300, Marcelo Tosatti <marcelo@kvack.org> wrote:
>> 
>> >Can you please try the attached patch.
>> >
>> >Grab a reference to the victim inode before calling vfs_unlink() to avoid
>> >it vanishing under us.
>> >
>> >diff --git a/fs/namei.c b/fs/namei.c
>> >index 42cce98..7993283 100644
>> >--- a/fs/namei.c
>> >+++ b/fs/namei.c
>> >@@ -1509,6 +1509,7 @@ asmlinkage long sys_unlink(const char * 
>> > 	char * name;
>> > 	struct dentry *dentry;
>> > 	struct nameidata nd;
>> >+	struct inode *inode = NULL;
>> > 
>> > 	name = getname(pathname);
>> > 	if(IS_ERR(name))
>> >@@ -1527,11 +1528,16 @@ asmlinkage long sys_unlink(const char * 
>> > 		/* Why not before? Because we want correct error value */
>> > 		if (nd.last.name[nd.last.len])
>> > 			goto slashes;
>> >+		inode = dentry->d_inode;
>> >+		if (inode)
>> >+			atomic_inc(&inode->i_count);
>> > 		error = vfs_unlink(nd.dentry->d_inode, dentry);
>> > 	exit2:
>> > 		dput(dentry);
>> > 	}
>
>Could you add this line here, because your oops still looks like the NULL
>is close to this area :
>
>+       printk(KERN_DEBUG "nd.dentry->d_inode = %p\n", nd.dentry->d_inode);

It didn't get there for the segfault case, gets there for local file 
delete 

After:
grant@sempro:~$ dmesg >dmesg
grant@sempro:~$ rm dmesg

Jun 19 08:49:17 sempro kernel: nd.dentry->d_inode = f73f4b80

After:
grant@sempro:~$ dmesg >/home/share/dmesg-test
grant@sempro:~$ rm /home/share/dmesg-test
Segmentation fault

Nothing reported by debug or syslog, oops in messages.

Cheers,
Grant.