linux-kernel - Re: kernel 3.8.4 : kernel BUG at fs/locks.c:2093! part #2

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Date:	Wed, 27 Mar 2013 18:20:42 +0100
From:	Toralf Förster <toralf.foerster@....de>
To:	"J. Bruce Fields" <bfields@...ldses.org>
CC:	Linux NFS mailing list <linux-nfs@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: kernel 3.8.4 : kernel BUG at fs/locks.c:2093!   part #2

On 03/26/2013 07:17 PM, J. Bruce Fields wrote:
> 
> Bah, too bad.  That patch was definitely not a fix, so there may be some
> race here.
> 
>> What I get at the host is now :
>>
>> 2013-03-26T18:32:17.487+01:00 n22 kernel: ------------[ cut here ]------------
>> 2013-03-26T18:32:17.487+01:00 n22 kernel: WARNING: at mm/page_alloc.c:2376 __alloc_pages_nodemask+0x262/0x7c0()
> ...
>> 2013-03-26T18:32:17.487+01:00 n22 kernel: [<c110f149>] __kmalloc+0x1b9/0x1e0
>> 2013-03-26T18:32:17.487+01:00 n22 kernel: [<f85835bf>] ? cache_check+0x22f/0x340 [sunrpc]
>> 2013-03-26T18:32:17.487+01:00 n22 kernel: [<f90a0b1c>] nfs4_acl_new+0x1c/0x30 [nfsd]
>> 2013-03-26T18:32:17.488+01:00 n22 kernel: [<f9095482>] nfsd4_decode_fattr+0x302/0x6c0 [nfsd]
> ...
> 
> A different bug, but thanks for catching it, I suspect the following is
> all we need.
> 
> --b.
> 
> commit 814d9d4f9164c3d778dadd093a54bb55d9a0c576
> Author: J. Bruce Fields <bfields@...hat.com>
> Date:   Tue Mar 26 14:11:13 2013 -0400
> 
>     nfsd4: reject "negative" acl lengths
>     
>     Since we only enforce an upper bound, not a lower bound, a "negative"
>     length can get through here.
>     
>     The symptom seen was a warning when we attempt to a kmalloc with an
>     excessive size.
>     
>     Reported-by: Toralf Förster <toralf.foerster@....de>
>     Signed-off-by: J. Bruce Fields <bfields@...hat.com>
> 
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 0dc1158..d1dd710 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -264,7 +264,7 @@ nfsd4_decode_fattr(struct nfsd4_compoundargs *argp, u32 *bmval,
>  		iattr->ia_valid |= ATTR_SIZE;
>  	}
>  	if (bmval[0] & FATTR4_WORD0_ACL) {
> -		int nace;
> +		u32 nace;
>  		struct nfs4_ace *ace;
>  
>  		READ_BUF(4); len += 4;
> 

I applied that patach on top of 3.8.4 and wonders now, whether the
following is the consequence :

$ df -m /tmp/forT/victims/
Filesystem     1M-blocks  Used Available Use% Mounted on
/dev/sdb3         183851 34907    139599  21% /

$ sudo ls -lh --color /tmp/forT/victims/f062
---xr-S--T 2 tfoerste users 985G Mar 27 18:15 /tmp/forT/victims/f062

ls shows a 1 TB file within a partition where just 34 MB are used at all
(its only one partition in that system and a separate small /boot too).

-- 
MfG/Sincerely
Toralf Förster
pgp finger print: 7B1A 07F4 EC82 0F90 D4C2 8936 872A E508 7DB6 9DA3
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