Re: [PATCH 0/2] nfsd: CB_GETATTR fixes

[Jeff Layton <jlayton@kernel.org>]

On Mon, 2024-08-26 at 10:37 -0400, Jeff Layton wrote:
> On Mon, 2024-08-26 at 09:22 +1000, NeilBrown wrote:
> > On Sun, 25 Aug 2024, Chuck Lever wrote:
> > > On Fri, Aug 23, 2024 at 06:27:37PM -0400, Jeff Layton wrote:
> > > > Fixes for a couple of CB_GETATTR bugs I found while working on the
> > > > delstid set. Mostly this just ensures that we hold references to the
> > > > delegation while working with it.
> > > > 
> > > > 
> > > 
> > > Applied to nfsd-fixes for v6.11-rc, thanks!
> > > 
> > > [1/2] nfsd: hold reference to delegation when updating it for cb_getattr
> > >       commit: 8fceb5f6636bbbf803fe29fff59f138206559964
> > > [2/2] nfsd: fix potential UAF in nfsd4_cb_getattr_release
> > >       commit: 8bc97f9b84c8852fcc56be2382f5115c518de785
> > > 
> > > -- 
> > > Chuck Lever
> > > 
> > 
> > Maybe the following can tidy up that code.  I can split this into
> > a few separate patches if you like.
> > Thoughts?
> > 
> > Note that the patch is easier to review if you apply it then use "git
> > diff -b".
> > 
> > NeilBrown
> > 
> > 
> > From: NeilBrown <neilb@suse.de>
> > Subject: [PATCH] nfsd: untangle code in nfsd4_deleg_getattr_conflict()
> > 
> > The code in nfsd4_deleg_getattr_conflict() is convoluted and buggy.
> > 
> > With this patch we:
> >  - properly handle non-nfsd leases.  We must not assume flc_owner is a
> >     delegation unless fl_lmops == &nfsd_lease_mng_ops
> 
> AFAICT, non-nfsd leases are already properly handled (though I do agree
> that the "flow" of this code is awkward). What case do you see that's
> wrong?
> 

Doh! Nevermind -- I see it now. It looks like the break_lease tag is
just in the wrong place. We should definitely fix that.

In any case, your patch looks reasonable to me, but I couldn't get it
to apply. Care to send a real PATCH instead? It's fine if you want to
drop my patch and just replace it with yours.

> >  - move the main code out of the for loop
> >  - have a single exit which calls nfs4_put_stid()
> >    (and other exits which don't need to call that)
> > 
> > Fixes: c5967721e106 ("NFSD: handle GETATTR conflict with write delegation")
> > Signed-off-by: NeilBrown <neilb@suse.de>
> > ---
> >  fs/nfsd/nfs4state.c | 130 ++++++++++++++++++++++----------------------
> >  1 file changed, 65 insertions(+), 65 deletions(-)
> > 
> > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > index 2c4b9a22b2bb..7672fa7a70f3 100644
> > --- a/fs/nfsd/nfs4state.c
> > +++ b/fs/nfsd/nfs4state.c
> > @@ -8837,6 +8837,7 @@ nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp, struct dentry *dentry,
> >  	struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
> >  	struct inode *inode = d_inode(dentry);
> >  	struct file_lock_context *ctx;
> > +	struct nfs4_delegation *dp = NULL;
> >  	struct nfs4_cb_fattr *ncf;
> >  	struct file_lease *fl;
> >  	struct iattr attrs;
> > @@ -8845,77 +8846,76 @@ nfsd4_deleg_getattr_conflict(struct svc_rqst *rqstp, struct dentry *dentry,
> >  	ctx = locks_inode_context(inode);
> >  	if (!ctx)
> >  		return 0;
> > +
> > +#define NON_NFSD_LEASE ((void*)1)
> > +
> >  	spin_lock(&ctx->flc_lock);
> >  	for_each_file_lock(fl, &ctx->flc_lease) {
> > -		unsigned char type = fl->c.flc_type;
> > -
> >  		if (fl->c.flc_flags == FL_LAYOUT)
> >  			continue;
> > -		if (fl->fl_lmops != &nfsd_lease_mng_ops) {
> > -			/*
> > -			 * non-nfs lease, if it's a lease with F_RDLCK then
> > -			 * we are done; there isn't any write delegation
> > -			 * on this inode
> > -			 */
> > -			if (type == F_RDLCK)
> > -				break;
> > -			goto break_lease;
> > -		}
> > -		if (type == F_WRLCK) {
> > -			struct nfs4_delegation *dp = fl->c.flc_owner;
> > -
> > -			if (dp->dl_recall.cb_clp == *(rqstp->rq_lease_breaker)) {
> > -				spin_unlock(&ctx->flc_lock);
> > -				return 0;
> > -			}
> > -break_lease:
> > -			nfsd_stats_wdeleg_getattr_inc(nn);
> > -			dp = fl->c.flc_owner;
> > -			refcount_inc(&dp->dl_stid.sc_count);
> > -			ncf = &dp->dl_cb_fattr;
> > -			nfs4_cb_getattr(&dp->dl_cb_fattr);
> > -			spin_unlock(&ctx->flc_lock);
> > -			wait_on_bit_timeout(&ncf->ncf_cb_flags, CB_GETATTR_BUSY,
> > -					TASK_INTERRUPTIBLE, NFSD_CB_GETATTR_TIMEOUT);
> > -			if (ncf->ncf_cb_status) {
> > -				/* Recall delegation only if client didn't respond */
> > -				status = nfserrno(nfsd_open_break_lease(inode, NFSD_MAY_READ));
> > -				if (status != nfserr_jukebox ||
> > -						!nfsd_wait_for_delegreturn(rqstp, inode)) {
> > -					nfs4_put_stid(&dp->dl_stid);
> > -					return status;
> > -				}
> > -			}
> > -			if (!ncf->ncf_file_modified &&
> > -					(ncf->ncf_initial_cinfo != ncf->ncf_cb_change ||
> > -					ncf->ncf_cur_fsize != ncf->ncf_cb_fsize))
> > -				ncf->ncf_file_modified = true;
> > -			if (ncf->ncf_file_modified) {
> > -				int err;
> > -
> > -				/*
> > -				 * Per section 10.4.3 of RFC 8881, the server would
> > -				 * not update the file's metadata with the client's
> > -				 * modified size
> > -				 */
> > -				attrs.ia_mtime = attrs.ia_ctime = current_time(inode);
> > -				attrs.ia_valid = ATTR_MTIME | ATTR_CTIME | ATTR_DELEG;
> > -				inode_lock(inode);
> > -				err = notify_change(&nop_mnt_idmap, dentry, &attrs, NULL);
> > -				inode_unlock(inode);
> > -				if (err) {
> > -					nfs4_put_stid(&dp->dl_stid);
> > -					return nfserrno(err);
> > -				}
> > -				ncf->ncf_cur_fsize = ncf->ncf_cb_fsize;
> > -				*size = ncf->ncf_cur_fsize;
> > -				*modified = true;
> > -			}
> > -			nfs4_put_stid(&dp->dl_stid);
> > -			return 0;
> > +		if (fl->c.flc_type == F_WRLCK) {
> > +			if (fl->fl_lmops == &nfsd_lease_mng_ops)
> > +				dp = fl->c.flc_owner;
> > +			else
> > +				dp = NON_NFSD_LEASE;
> >  		}
> >  		break;
> >  	}
> > +	if (dp == NULL || dp == NON_NFSD_LEASE ||
> > +	    dp->dl_recall.cb_clp == *(rqstp->rq_lease_breaker)) {
> > +		spin_unlock(&ctx->flc_lock);
> > +		if (dp == NON_NFSD_LEASE) {
> > +			status = nfserrno(nfsd_open_break_lease(inode,
> > +								NFSD_MAY_READ));
> > +			if (status != nfserr_jukebox ||
> > +			    !nfsd_wait_for_delegreturn(rqstp, inode))
> > +				return status;
> > +		}
> > +		return 0;
> > +	}
> > +
> > +	nfsd_stats_wdeleg_getattr_inc(nn);
> > +	refcount_inc(&dp->dl_stid.sc_count);
> > +	ncf = &dp->dl_cb_fattr;
> > +	nfs4_cb_getattr(&dp->dl_cb_fattr);
> >  	spin_unlock(&ctx->flc_lock);
> > -	return 0;
> > +
> > +	wait_on_bit_timeout(&ncf->ncf_cb_flags, CB_GETATTR_BUSY,
> > +			    TASK_INTERRUPTIBLE, NFSD_CB_GETATTR_TIMEOUT);
> > +	if (ncf->ncf_cb_status) {
> > +		/* Recall delegation only if client didn't respond */
> > +		status = nfserrno(nfsd_open_break_lease(inode, NFSD_MAY_READ));
> > +		if (status != nfserr_jukebox ||
> > +		    !nfsd_wait_for_delegreturn(rqstp, inode))
> > +			goto out_status;
> > +	}
> > +	if (!ncf->ncf_file_modified &&
> > +	    (ncf->ncf_initial_cinfo != ncf->ncf_cb_change ||
> > +	     ncf->ncf_cur_fsize != ncf->ncf_cb_fsize))
> > +		ncf->ncf_file_modified = true;
> > +	if (ncf->ncf_file_modified) {
> > +		int err;
> > +
> > +		/*
> > +		 * Per section 10.4.3 of RFC 8881, the server would
> > +		 * not update the file's metadata with the client's
> > +		 * modified size
> > +		 */
> > +		attrs.ia_mtime = attrs.ia_ctime = current_time(inode);
> > +		attrs.ia_valid = ATTR_MTIME | ATTR_CTIME | ATTR_DELEG;
> > +		inode_lock(inode);
> > +		err = notify_change(&nop_mnt_idmap, dentry, &attrs, NULL);
> > +		inode_unlock(inode);
> > +		if (err) {
> > +			status = nfserrno(err);
> > +			goto out_status;
> > +		}
> > +		ncf->ncf_cur_fsize = ncf->ncf_cb_fsize;
> > +		*size = ncf->ncf_cur_fsize;
> > +		*modified = true;
> > +	}
> > +	status = 0;
> > +out_status:
> > +	nfs4_put_stid(&dp->dl_stid);
> > +	return status;
> >  }
> 
> Patch looks like a nice cleanup, but I don't think the Fixes tag is
> appropriate here.

-- 
Jeff Layton <jlayton@kernel.org>