linux-kernel - Re: [PATCH][Resend] coredump: call vfs

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Date:	Tue, 28 Jun 2011 19:26:01 -0400
From:	Trond Myklebust <Trond.Myklebust@...app.com>
To:	Arnaud Giersch <arnaud.giersch@...e.fr>
Cc:	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH][Resend] coredump: call vfs_getattr() to get inode
 attributes

On Tue, 2011-06-28 at 23:19 +0200, Arnaud Giersch wrote: 
> From: Arnaud Giersch <arnaud.giersch@...e.fr>
> 
> In do_coredump(), call vfs_getattr() to get inode attributes, and do not
> get them directly from the fields of the inode struct.
> 
> Without this patch, when dumping core on an NFSv4 mount, and the i_uid
> field is not correctly filled at open time, the uid check fails, and an
> empty core dump is produced.
> 
> This apparently only happens when there was no "core" file before the
> dump.  If a "core" file owned by the current user is already present, it
> is correctly filled.
> 
> The reason is that decode_attr_owner() in fs/nfs/nfs4xdr.c is not
> allowed to call the idmapper when it receives may_sleep = 0 (see commit
> 80e52aced138bb41b045a8595a87510f27d8d8c5, and some explanations in
> http://article.gmane.org/gmane.linux.nfs/33391).
> 
> Signed-off-by: Arnaud Giersch <arnaud.giersch@...e.fr>

This wants to be fixed in the NFS layer, not the VFS.

What we should do is the following:

     1. Save the string versions of user@...ain/group@...ain in the
        struct nfs4_opendata so that we can resolve them from the
        process context in _nfs4_proc_open(). 
     2. Fix nfs4_atomic_open() so that it revalidates any inode that has
        the NFS_INO_INVALID_ATTR flag set.

Cheers
   Trond
-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@...app.com
www.netapp.com

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