Re: [PATCH v2] nfsd: inherit required unset default acls from effective set

[Jeff Layton]

On Mon, 2023-07-24 at 09:44 -0400, Chuck Lever wrote:
> On Mon, Jul 24, 2023 at 08:13:05AM -0400, Jeff Layton wrote:
> > A well-formed NFSv4 ACL will always contain OWNER@/GROUP@/EVERYONE@
> > ACEs, but there is no requirement for inheritable entries for those
> > entities. POSIX ACLs must always have owner/group/other entries, even for a
> > default ACL.
> > 
> > nfsd builds the default ACL from inheritable ACEs, but the current code
> > just leaves any unspecified ACEs zeroed out. The result is that adding a
> > default user or group ACE to an inode can leave it with unwanted deny
> > entries.
> > 
> > For instance, a newly created directory with no acl will look something
> > like this:
> > 
> > 	# NFSv4 translation by server
> > 	A::OWNER@:rwaDxtTcCy
> > 	A::GROUP@:rxtcy
> > 	A::EVERYONE@:rxtcy
> > 
> > 	# POSIX ACL of underlying file
> > 	user::rwx
> > 	group::r-x
> > 	other::r-x
> > 
> > ...if I then add new v4 ACE:
> > 
> > 	nfs4_setfacl -a A:fd:1000:rwx /mnt/local/test
> > 
> > ...I end up with a result like this today:
> > 
> > 	user::rwx
> > 	user:1000:rwx
> > 	group::r-x
> > 	mask::rwx
> > 	other::r-x
> > 	default:user::---
> > 	default:user:1000:rwx
> > 	default:group::---
> > 	default:mask::rwx
> > 	default:other::---
> > 
> > 	A::OWNER@:rwaDxtTcCy
> > 	A::1000:rwaDxtcy
> > 	A::GROUP@:rxtcy
> > 	A::EVERYONE@:rxtcy
> > 	D:fdi:OWNER@:rwaDx
> > 	A:fdi:OWNER@:tTcCy
> > 	A:fdi:1000:rwaDxtcy
> > 	A:fdi:GROUP@:tcy
> > 	A:fdi:EVERYONE@:tcy
> > 
> > ...which is not at all expected. Adding a single inheritable allow ACE
> > should not result in everyone else losing access.
> > 
> > The setfacl command solves a silimar issue by copying owner/group/other
> > entries from the effective ACL when none of them are set:
> > 
> >     "If a Default ACL entry is created, and the  Default  ACL  contains  no
> >      owner,  owning group,  or  others  entry,  a  copy of the ACL owner,
> >      owning group, or others entry is added to the Default ACL.
> > 
> > Having nfsd do the same provides a more sane result (with no deny ACEs
> > in the resulting set):
> > 
> > 	user::rwx
> > 	user:1000:rwx
> > 	group::r-x
> > 	mask::rwx
> > 	other::r-x
> > 	default:user::rwx
> > 	default:user:1000:rwx
> > 	default:group::r-x
> > 	default:mask::rwx
> > 	default:other::r-x
> > 
> > 	A::OWNER@:rwaDxtTcCy
> > 	A::1000:rwaDxtcy
> > 	A::GROUP@:rxtcy
> > 	A::EVERYONE@:rxtcy
> > 	A:fdi:OWNER@:rwaDxtTcCy
> > 	A:fdi:1000:rwaDxtcy
> > 	A:fdi:GROUP@:rxtcy
> > 	A:fdi:EVERYONE@:rxtcy
> > 
> > Reported-by: Ondrej Valousek <ondrej.valousek@xxxxxxxxxxx>
> > Closes: https://bugzilla.redhat.com/show_bug.cgi?id=2136452
> > Suggested-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> > ---
> > Changes in v2:
> > - always set missing ACEs whenever default ACL has any ACEs that are
> >   explicitly set. This better conforms to how setfacl works.
> > - drop now-unneeded "empty" boolean
> > - Link to v1: https://lore.kernel.org/r/20230719-nfsd-acl-v1-1-eb0faf3d2917@xxxxxxxxxx
> > ---
> >  fs/nfsd/nfs4acl.c | 32 ++++++++++++++++++++++++++++----
> >  1 file changed, 28 insertions(+), 4 deletions(-)
> > 
> > diff --git a/fs/nfsd/nfs4acl.c b/fs/nfsd/nfs4acl.c
> > index 518203821790..b931d4383517 100644
> > --- a/fs/nfsd/nfs4acl.c
> > +++ b/fs/nfsd/nfs4acl.c
> > @@ -441,7 +441,7 @@ struct posix_ace_state_array {
> >   * calculated so far: */
> >  
> >  struct posix_acl_state {
> > -	int empty;
> > +	unsigned char valid;
> >  	struct posix_ace_state owner;
> >  	struct posix_ace_state group;
> >  	struct posix_ace_state other;
> > @@ -457,7 +457,6 @@ init_state(struct posix_acl_state *state, int cnt)
> >  	int alloc;
> >  
> >  	memset(state, 0, sizeof(struct posix_acl_state));
> > -	state->empty = 1;
> >  	/*
> >  	 * In the worst case, each individual acl could be for a distinct
> >  	 * named user or group, but we don't know which, so we allocate
> > @@ -500,7 +499,7 @@ posix_state_to_acl(struct posix_acl_state *state, unsigned int flags)
> >  	 * and effective cases: when there are no inheritable ACEs,
> >  	 * calls ->set_acl with a NULL ACL structure.
> >  	 */
> > -	if (state->empty && (flags & NFS4_ACL_TYPE_DEFAULT))
> > +	if (!state->valid && (flags & NFS4_ACL_TYPE_DEFAULT))
> >  		return NULL;
> >  
> >  	/*
> > @@ -622,9 +621,10 @@ static void process_one_v4_ace(struct posix_acl_state *state,
> >  				struct nfs4_ace *ace)
> >  {
> >  	u32 mask = ace->access_mask;
> > +	short type = ace2type(ace);
> >  	int i;
> >  
> > -	state->empty = 0;
> > +	state->valid |= type;
> >  
> >  	switch (ace2type(ace)) {
> 
> Mechanical issue: the patch adds @type, but uses it just once.
> The switch here also wants the value of ace2type(ace).
> 
> 

Doh! I had that fixed in one version of the patch, but had to rework the
branch and lost that delta. I can respin, or if you just want to fix
that in place, then that would be fine too.

> >  	case ACL_USER_OBJ:
> > @@ -726,6 +726,30 @@ static int nfs4_acl_nfsv4_to_posix(struct nfs4_acl *acl,
> >  		if (!(ace->flag & NFS4_ACE_INHERIT_ONLY_ACE))
> >  			process_one_v4_ace(&effective_acl_state, ace);
> >  	}
> > +
> > +	/*
> > +	 * At this point, the default ACL may have zeroed-out entries for owner,
> > +	 * group and other. That usually results in a non-sensical resulting ACL
> > +	 * that denies all access except to any ACE that was explicitly added.
> > +	 *
> > +	 * The setfacl command solves a similar problem with this logic:
> > +	 *
> > +	 * "If  a  Default  ACL  entry is created, and the Default ACL contains
> > +	 *  no owner, owning group, or others entry,  a  copy of  the  ACL
> > +	 *  owner, owning group, or others entry is added to the Default ACL."
> > +	 *
> > +	 * Copy any missing ACEs from the effective set, if any ACEs were
> > +	 * explicitly set.
> > +	 */
> > +	if (default_acl_state.valid) {
> > +		if (!(default_acl_state.valid & ACL_USER_OBJ))
> > +			default_acl_state.owner = effective_acl_state.owner;
> > +		if (!(default_acl_state.valid & ACL_GROUP_OBJ))
> > +			default_acl_state.group = effective_acl_state.group;
> > +		if (!(default_acl_state.valid & ACL_OTHER))
> > +			default_acl_state.other = effective_acl_state.other;
> > +	}
> > +
> >  	*pacl = posix_state_to_acl(&effective_acl_state, flags);
> >  	if (IS_ERR(*pacl)) {
> >  		ret = PTR_ERR(*pacl);
> > 
> > ---
> > base-commit: 7bfb36a2ee1d329a501ba4781db4145dc951c798
> > change-id: 20230719-nfsd-acl-5ab61537e4e6
> > 
> > Best regards,
> > -- 
> > Jeff Layton <jlayton@xxxxxxxxxx>
> > 
> 

-- 
Jeff Layton <jlayton@xxxxxxxxxx>