display project quota as user

display project quota as user

[Andre Noll]

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Simple question: Can non-privileged users display XFS project quotas?

Currently the command

	xfs_quota -c 'quota -p 42'

fails when executed as a non-root user due to quotactl(Q_XGETQUOTA,...)
returning EPERM. The problem seems to be that fs/quota/quota.c has no
knowledge of project quotas at all.

The proof-of-concept patch below makes quotactl(Q_XGETQUOTA,...)
succeed for any user when called with type == XQM_PRJQUOTA. However,
relaxing the permission checks like this might not please everybody,
changes semantics of an existing API and adds the XFS specific constant
XQM_PRJQUOTA to fs/quota.c. So I'm not even asking to apply something
like that.

Is there a better way to allow users to display project quotas?

Thanks
Andre
---

diff --git a/fs/quota/quota.c b/fs/quota/quota.c
index fc2c438..010763d 100644
--- a/fs/quota/quota.c
+++ b/fs/quota/quota.c
@@ -33,7 +33,8 @@ static int check_quotactl_permission(struct super_block *sb, int type, int cmd,
 	case Q_GETQUOTA:
 	case Q_XGETQUOTA:
 		if ((type == USRQUOTA && current_euid() == id) ||
-		    (type == GRPQUOTA && in_egroup_p(id)))
+		    (type == GRPQUOTA && in_egroup_p(id)) ||
+		    (type == XQM_PRJQUOTA))
 			break;
 		/*FALLTHROUGH*/
 	default:
-- 
The only person who always got his work done by Friday was Robinson Crusoe

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Re: display project quota as user

[Dave Chinner]

On Wed, Mar 14, 2012 at 02:09:02PM +0100, Andre Noll wrote:
> Simple question: Can non-privileged users display XFS project quotas?
> 
> Currently the command
> 
> 	xfs_quota -c 'quota -p 42'
> 
> fails when executed as a non-root user due to quotactl(Q_XGETQUOTA,...)
> returning EPERM. The problem seems to be that fs/quota/quota.c has no
> knowledge of project quotas at all.

Right - only XFS supports project quotas.

> The proof-of-concept patch below makes quotactl(Q_XGETQUOTA,...)
> succeed for any user when called with type == XQM_PRJQUOTA. However,
> relaxing the permission checks like this might not please everybody,
> changes semantics of an existing API and adds the XFS specific constant
> XQM_PRJQUOTA to fs/quota.c. So I'm not even asking to apply something
> like that.
> 
> Is there a better way to allow users to display project quotas?

There is no user <=> projid mapping that exists, so either the
information is available to everyone, or it is available only to
root. In this case, system wide quota reports are limited to root,
and I don't see that changing.

If you really must allow users to see project quota limits, then
write a simple wrapper program and allow only the users that need
the infomration to execute it via sudo....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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Re: display project quota as user

[Andre Noll]

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On Thu, Mar 15, 10:31, Dave Chinner wrote:
> > Is there a better way to allow users to display project quotas?
> 
> There is no user <=> projid mapping that exists, so either the
> information is available to everyone, or it is available only to
> root. In this case, system wide quota reports are limited to root,
> and I don't see that changing.
> 
> If you really must allow users to see project quota limits, then
> write a simple wrapper program and allow only the users that need
> the infomration to execute it via sudo....

OK, will do that. Thanks for the clarification.

Andre
-- 
The only person who always got his work done by Friday was Robinson Crusoe

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