Subject: Re: [PATCH 2/4] autofs4 - track uid and gid of last mount requester
From: Ian Kent <raven@themaw.net>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: autofs@linux.kernel.org, linux-kernel@vger.kernel.org,
       linux-fsdevel@vger.kernel.org, containers@lists.osdl.org
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	 <1218165931.17093.58.camel@raven.themaw.net>
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Date: Fri, 08 Aug 2008 13:37:41 +0800
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On Fri, 2008-08-08 at 11:25 +0800, Ian Kent wrote:
> On Thu, 2008-08-07 at 13:46 -0700, Andrew Morton wrote:
> > On Thu, 07 Aug 2008 19:40:14 +0800
> > Ian Kent <raven@themaw.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@themaw.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.
> > > +	 */
> > > +	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?
> 
> We didn't really get to the bottom of that last time I posted this but
> hopefully Serge will get right on this and we can sort out what, idf
> anything I need to do.

But, at this stage, I believe that if namespaces are being used then
there would also need to be a daemon within the container which would
have the same namespace view as other processes in the container. I
expect that the situation is not nearly as straight forward as I think
so I'll need to wait for further comments.

Ian


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