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

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Date:	Tue, 26 Mar 2013 14:17:17 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Toralf Förster <toralf.foerster@....de>
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 Tue, Mar 26, 2013 at 06:46:31PM +0100, Toralf Förster wrote:
> On 03/26/2013 03:46 PM, J. Bruce Fields wrote:
> > Can you run with test patches?
> > 
> > This just makes nfsd's fput calls synchronous so that we see in the
> > backtrace who called them.
> 
> Well - the patched 3.8.4 host kernel now survives the stress test of the UML system.

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;
--
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