linux-kernel - Re: [patch 1/3] NFS: fix potential NULL pointer dereference

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Message-ID: <aa79d98a0804162125u45bde1edq550acf51784a5b5@mail.gmail.com>
Date:	Thu, 17 Apr 2008 08:25:32 +0400
From:	"Cyrill Gorcunov" <gorcunov@...il.com>
To:	"Trond Myklebust" <trond.myklebust@....uio.no>
Cc:	bfields@...ldses.org, neilb@...e.de, ibm-acpi@....eng.br,
	len.brown@...el.com, kkeil@...e.de, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 1/3] NFS: fix potential NULL pointer dereference

On Thu, Apr 17, 2008 at 12:40 AM, Trond Myklebust
<trond.myklebust@....uio.no> wrote:
>
>  On Thu, 2008-04-17 at 00:19 +0400, Cyrill Gorcunov wrote:
>  > Trond, I've just pointed the problem and its solution (which is seems
>  > to be a bit ugly, according to the rest nfs coding principle). So if
>  > you prefer to have such a check in 'walk_path' function - just say me
>  > that. You choose :) Thanks for comments
>
>
> > > So? The defensive coding principle is that you perform validity checks
>  > > when the pointer is created. Otherwise, we could equally well have added
>  > > the NULL deref check to nfs4_path_walk()...
>
>  No, your fix was correct, it was just incomplete.
>
>  The point I was making above was that defensive programming means that
>  _all_ these validity/NULL pointer checks should really be done in
>  nfs4_validate_mount_data and nfs_validate_mount_data. We shouldn't rely
>  on checks in other parts of the code.
>
>  In fact, as an example: it looks to me as if the lack of a
>  nfs_server.hostname, leads to a lack of nfs_client->cl_hostname, which
>  will eventually cause an Oops if you 'cat /proc/fs/nfsfs/servers', or if
>  you hit the printk in nfs_update_inode(), or various other dprintk()s.
>
>  Trond
>
>

Thanks Trond, I'll remake it ASAP (but can't guarantie that it will be soon ;)
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