linux-kernel - Re: linux-3.14 nfsd regression

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Message-ID: <5362350A.6040402@pobox.com>
Date:	Thu, 01 May 2014 07:50:34 -0400
From:	Mark Lord <mlord@...ox.com>
To:	"J. Bruce Fields" <bfields@...ldses.org>,
	Jeff Layton <jlayton@...hat.com>
CC:	"J. Bruce Fields" <bfields@...hat.com>, Albert Fluegel <af@....de>,
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: linux-3.14 nfsd regression

On 14-04-04 09:58 AM, J. Bruce Fields wrote:
> On Thu, Apr 03, 2014 at 07:21:46PM -0400, Jeff Layton wrote:
>> So according to the RFC you have to encode both the mode bits and the
>> ftype for v2. The type bits seem to be removed from the mode in NFSv3
>> though, so perhaps we should only be doing that masking in versions
>> above v2?
> 
> Right, the problematic patch applied the same mask in both v2 and v3
> cases, so I'm reverting just the v2 part (see below).
> 
>> With a quick check, it looks like the v3 code doesn't rely on those bits
>> and I imagine v4 doesn't either.
>>
>> It might also be nice to have the client v2 decode_fattr function to
>> throw a warning if the server sends us mismatched type bits and ftype
>> values. That would have helped us catch this sooner...
> 
> Yes, that might be a reasonable thing to do, though I don't know if it's
> worth it.
> 
> --b.
> 
> commit 35a8dff14e76c00e5b52140290cfb498dc2454a0
> Author: J. Bruce Fields <bfields@...hat.com>
> Date:   Thu Apr 3 15:10:35 2014 -0400
> 
>     nfsd: revert v2 half of "nfsd: don't return high mode bits"
>     
>     This reverts the part of commit 6e14b46b91fee8a049b0940333ce13a820beaaa5
>     that changes NFSv2 behavior.
>     
>     Mark Lord found that it broke nfs-root for Linux clients, because it
>     broke NFSv2.
>     
>     In fact, from RFC 1094:
>     
>     	"Notice that the file type is specified both in the mode bits
>     	and in the file type.  This is really a bug in the protocol and
>     	will be fixed in future versions."
>     
>     So NFSv2 clients really are expected to depend on the high bits of the
>     mode.
>     
>     Cc: stable@...nel.org
>     Reported-by: Mark Lord <mlord@...ox.com>
>     Signed-off-by: J. Bruce Fields <bfields@...hat.com>
> 
> diff --git a/fs/nfsd/nfsxdr.c b/fs/nfsd/nfsxdr.c
> index b17d932..9c769a4 100644
> --- a/fs/nfsd/nfsxdr.c
> +++ b/fs/nfsd/nfsxdr.c
> @@ -152,7 +152,7 @@ encode_fattr(struct svc_rqst *rqstp, __be32 *p, struct svc_fh *fhp,
>  	type = (stat->mode & S_IFMT);
>  
>  	*p++ = htonl(nfs_ftypes[type >> 12]);
> -	*p++ = htonl((u32) (stat->mode & S_IALLUGO));
> +	*p++ = htonl((u32) stat->mode);
>  	*p++ = htonl((u32) stat->nlink);
>  	*p++ = htonl((u32) from_kuid(&init_user_ns, stat->uid));
>  	*p++ = htonl((u32) from_kgid(&init_user_ns, stat->gid));
> 


Still a regression in 3.14.2 now.
Anyone got plans to push this patch out to mainline, as well as +stable ?

-- 
Mark Lord
Real-Time Remedies Inc.
mlord@...ox.com
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