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SubjectRe: [NFS] NFSv2/3 broken exporting/mounting (permission denied) in 2.6.24-rc4
In message <20071207025504.GA3070@fieldses.org>, "J. Bruce Fields" writes:
> On Thu, Dec 06, 2007 at 09:20:41PM -0500, Erez Zadok wrote:
> > I get a "permission denied" when trying to mount a localhost nfsv2/3
> > exported volume, on v2.6.24-rc4-124-gf194d13. It works w/ nfsv4 mounting.
> > It worked fine in 2.6.24-rc3. Here's a sequence of ops I tried:
> >
> > # mount -t ext2 /dev/hdb1 /n/lower/b0
> > # exportfs -o no_root_squash,rw localhost:/n/lower/b0
> > # mount -t nfs -o nfsvers=3 localhost:/n/lower/b0 /mnt
>
> What do you see if you watch the network traffic in ethereal?
>
> --b.

Bruce, I'm using nfs-utils-1.0.10-14.fc6 on an FC6 system with all latest
FC6 patches. Using git-bisect I was able to find the patch which broke it:

commit 2b1e300a9dfc3196ccddf6f1d74b91b7af55e416
Author: Eric W. Biederman <ebiederm@xmission.com>
Date: Sun Dec 2 00:33:17 2007 +1100

[NETNS]: Fix /proc/net breakage

Well I clearly goofed when I added the initial network namespace support
for /proc/net. Currently things work but there are odd details visible to
user space, even when we have a single network namespace.

Since we do not cache proc_dir_entry dentries at the moment we can just
modify ->lookup to return a different directory inode depending on the
network namespace of the process looking at /proc/net, replacing the
current technique of using a magic and fragile follow_link method.

To accomplish that this patch:
- introduces a shadow_proc method to allow different dentries to
be returned from proc_lookup.
- Removes the old /proc/net follow_link magic
- Fixes a weakness in our not caching of proc generic dentries.

As shadow_proc uses a task struct to decided which dentry to return we can
go back later and fix the proc generic caching without modifying any code
that uses the shadow_proc method.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

With the above patch, rpc.mountd is unable to open /proc/fs/nfsd/filehandle.
Strace shows:

open("/proc/fs/nfsd/filehandle", O_RDWR|O_LARGEFILE) = -1 ENOENT (No such file or directory)
Without the above patch, /proc/fs/nfsd is populated with a number of files,
including "filehandle".

Erez.


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