[PATCH] rpc.mountd: Turn off root_squash on pseudo roots, its not needed.

[PATCH] rpc.mountd: Turn off root_squash on pseudo roots, its not needed.

[Steve Dickson]

Hello,

It turns out the setting of NFSEXP_ROOTSQUASH option
on pseudo roots breaks v4 exports when the no_root_squash
is set on the 'real' export. For example,

The export:

    /home/user/dir  *(rw,no_root_squash)

the /home/user directory has the 0700 permission modes

Now from an v4 enabled client do the following mount
will fail with permission denied. 
   mount server:/home/user/dir /mnt

The reason being, the 'no_root_squash' option is only
being applied to the 'dir' part of the path. So then
root tries to lookup the 'user' part, its denied. 

Now turns out the NFSEXP_ROOTSQUASH option is not need
to be set on pseudo roots because one, they are marked
as read only and two only the export part of the path 
are exposed if by chance the actual pseudo root is 
mounted. For example:
    # mount server:/ /mnt
    # ls /mnt
     ./  ../  home/
    # ls /mnt/home
    ./  ../  user/

only the above directories would be shown and they would be 
read-only

steved.


Currently the default setting of a pseudo root is to have
NFSEXP_ROOTSQUASH enabled. This setting will cause the looking
up of real export to fail when have the no_root_squash set.

It turns the setting of NFSEXP_ROOTSQUASH is not needed on pseudo
roots for two reasons. 1) pseudo roots are marked as read-only so
they can not be written on. 2) pseudo roots only show exported
entries when they are mounted.

Signed-off-by: Steve Dickson <steved@redhat.com>
---
 utils/mountd/v4root.c |    5 ++---
 1 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/utils/mountd/v4root.c b/utils/mountd/v4root.c
index 7fd6af3..41b77eb 100644
--- a/utils/mountd/v4root.c
+++ b/utils/mountd/v4root.c
@@ -35,9 +35,8 @@ static nfs_export pseudo_root = {
 	.m_export = {
 		.e_hostname = "*",
 		.e_path = "/",
-		.e_flags = NFSEXP_READONLY | NFSEXP_ROOTSQUASH
-				| NFSEXP_NOSUBTREECHECK | NFSEXP_FSID
-				| NFSEXP_V4ROOT,
+		.e_flags = NFSEXP_READONLY | NFSEXP_NOSUBTREECHECK | 
+				NFSEXP_FSID | NFSEXP_V4ROOT,
 		.e_anonuid = 65534,
 		.e_anongid = 65534,
 		.e_squids = NULL,

Re: [PATCH] rpc.mountd: Turn off root_squash on pseudo roots, its not needed.

[J. Bruce Fields]

On Wed, Jun 02, 2010 at 05:14:03PM -0400, Steve Dickson wrote:
> Hello,
> 
> It turns out the setting of NFSEXP_ROOTSQUASH option
> on pseudo roots breaks v4 exports when the no_root_squash
> is set on the 'real' export. For example,

I remember thinking about this sort of case as we were working on this,
but can't remember why I left ROOTSQUASH set.  I think it may just have
been paranoia, combined with skepticism that anyone would want to
nfs-export a filesystem that could only be looked up by root.

Apparently someone is?  I'd still be curious why.  But I think your
patch is right; for what it's worth:

	Acked-by: J. Bruce Fields <bfields@citi.umich.edu>

--b.

> 
> The export:
> 
>     /home/user/dir  *(rw,no_root_squash)
> 
> the /home/user directory has the 0700 permission modes
> 
> Now from an v4 enabled client do the following mount
> will fail with permission denied. 
>    mount server:/home/user/dir /mnt
> 
> The reason being, the 'no_root_squash' option is only
> being applied to the 'dir' part of the path. So then
> root tries to lookup the 'user' part, its denied. 
> 
> Now turns out the NFSEXP_ROOTSQUASH option is not need
> to be set on pseudo roots because one, they are marked
> as read only and two only the export part of the path 
> are exposed if by chance the actual pseudo root is 
> mounted. For example:
>     # mount server:/ /mnt
>     # ls /mnt
>      ./  ../  home/
>     # ls /mnt/home
>     ./  ../  user/
> 
> only the above directories would be shown and they would be 
> read-only
> 
> steved.
> 
> 
> Currently the default setting of a pseudo root is to have
> NFSEXP_ROOTSQUASH enabled. This setting will cause the looking
> up of real export to fail when have the no_root_squash set.
> 
> It turns the setting of NFSEXP_ROOTSQUASH is not needed on pseudo
> roots for two reasons. 1) pseudo roots are marked as read-only so
> they can not be written on. 2) pseudo roots only show exported
> entries when they are mounted.
> 
> Signed-off-by: Steve Dickson <steved@redhat.com>
> ---
>  utils/mountd/v4root.c |    5 ++---
>  1 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/utils/mountd/v4root.c b/utils/mountd/v4root.c
> index 7fd6af3..41b77eb 100644
> --- a/utils/mountd/v4root.c
> +++ b/utils/mountd/v4root.c
> @@ -35,9 +35,8 @@ static nfs_export pseudo_root = {
>  	.m_export = {
>  		.e_hostname = "*",
>  		.e_path = "/",
> -		.e_flags = NFSEXP_READONLY | NFSEXP_ROOTSQUASH
> -				| NFSEXP_NOSUBTREECHECK | NFSEXP_FSID
> -				| NFSEXP_V4ROOT,
> +		.e_flags = NFSEXP_READONLY | NFSEXP_NOSUBTREECHECK | 
> +				NFSEXP_FSID | NFSEXP_V4ROOT,
>  		.e_anonuid = 65534,
>  		.e_anongid = 65534,
>  		.e_squids = NULL,
> 
> 
> --
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