linux-kernel - Re: [PATCH 2/4] autofs4 - track uid and gid of last mount requester

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Message-ID: <20080807221558.GA27863@us.ibm.com>
Date:	Thu, 7 Aug 2008 17:15:58 -0500
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Ian Kent <raven@...maw.net>, autofs@...ux.kernel.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	containers@...ts.osdl.org
Subject: Re: [PATCH 2/4] autofs4 - track uid and gid of last mount requester

Quoting Andrew Morton (akpm@...ux-foundation.org):
> On Thu, 07 Aug 2008 19:40:14 +0800
> Ian Kent <raven@...maw.net> wrote:
> 
> > Patch to track the uid and gid of the last process to request a mount
> > for on an autofs dentry.
> 
> pet peeve: changelog should not tell the reader that this is a "patch".
> Because when someone is reading the changelog in the git repository,
> they hopefully already know that.
> 
> > Signed-off-by: Ian Kent <raven@...maw.net>
> > 
> > ---
> > 
> >  fs/autofs4/autofs_i.h |    3 +++
> >  fs/autofs4/inode.c    |    2 ++
> >  fs/autofs4/waitq.c    |   34 ++++++++++++++++++++++++++++++++++
> >  3 files changed, 39 insertions(+), 0 deletions(-)
> > 
> > 
> > diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
> > index ea024d8..fa76d18 100644
> > --- a/fs/autofs4/autofs_i.h
> > +++ b/fs/autofs4/autofs_i.h
> > @@ -63,6 +63,9 @@ struct autofs_info {
> >  	unsigned long last_used;
> >  	atomic_t count;
> >  
> > +	uid_t uid;
> > +	gid_t gid;
> > +
> >  	mode_t	mode;
> >  	size_t	size;
> >  
> > diff --git a/fs/autofs4/inode.c b/fs/autofs4/inode.c
> > index 9ca2d07..9408507 100644
> > --- a/fs/autofs4/inode.c
> > +++ b/fs/autofs4/inode.c
> > @@ -53,6 +53,8 @@ struct autofs_info *autofs4_init_ino(struct autofs_info *ino,
> >  		atomic_set(&ino->count, 0);
> >  	}
> >  
> > +	ino->uid = 0;
> > +	ino->gid = 0;
> >  	ino->mode = mode;
> >  	ino->last_used = jiffies;
> >  
> > diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
> > index 6d87bb1..7c60c0b 100644
> > --- a/fs/autofs4/waitq.c
> > +++ b/fs/autofs4/waitq.c
> > @@ -457,6 +457,40 @@ int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
> >  
> >  	status = wq->status;
> >  
> > +	/*
> > +	 * For direct and offset mounts we need to track the requestrer
> 
> typo which I'll fix.
> 
> > +	 * uid and gid in the dentry info struct. This is so it can be
> > +	 * supplied, on request, by the misc device ioctl interface.
> > +	 * This is needed during daemon resatart when reconnecting
> > +	 * to existing, active, autofs mounts. The uid and gid (and
> > +	 * related string values) may be used for macro substitution
> > +	 * in autofs mount maps.

Hi Ian,

could you say just a few more words on these macro substitution?

I think your use of uids can completely ignore user namespaces, but it
depends on who does the macro substitutions and how...

thanks,
-serge

> > +	 */
> > +	if (!status) {
> > +		struct autofs_info *ino;
> > +		struct dentry *de = NULL;
> > +
> > +		/* direct mount or browsable map */
> > +		ino = autofs4_dentry_ino(dentry);
> > +		if (!ino) {
> > +			/* If not lookup actual dentry used */
> > +			de = d_lookup(dentry->d_parent, &dentry->d_name);
> > +			if (de)
> > +				ino = autofs4_dentry_ino(de);
> > +		}
> > +
> > +		/* Set mount requester */
> > +		if (ino) {
> > +			spin_lock(&sbi->fs_lock);
> > +			ino->uid = wq->uid;
> > +			ino->gid = wq->gid;
> > +			spin_unlock(&sbi->fs_lock);
> > +		}
> > +
> > +		if (de)
> > +			dput(de);
> > +	}
> > +
> 
> Please remind me again why autofs's use of current->uid and
> current->gid is not busted in the presence of PID namespaces, where
> these things are no longer system-wide unique?
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