2007-12-07 21:08:04

by Bruce Fields

[permalink] [raw]
Subject: Re: [NFS] NFSv2/3 broken exporting/mounting (permission denied) in 2.6.24-rc4

On Fri, Dec 07, 2007 at 03:00:13PM -0500, Erez Zadok wrote:
> In message <[email protected]>, "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:

Wow, thanks for your work finding that.

> commit 2b1e300a9dfc3196ccddf6f1d74b91b7af55e416
> Author: Eric W. Biederman <[email protected]>
> 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 <[email protected]>
> Cc: "Rafael J. Wysocki" <[email protected]>
> Cc: Pavel Machek <[email protected]>
> Cc: Pavel Emelyanov <[email protected]>
> Cc: "David S. Miller" <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Signed-off-by: Andrew Morton <[email protected]>
> Signed-off-by: Herbert Xu <[email protected]>
> 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".

Those files are actually in a separate filesystem (of type "nfsd") which
is supposed to be mounted on /proc/fs/nfsd/. So that mount must have
failed in the bad case? It's not immediately obvious to me what this
patch has to do with that. Hm.


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