Re: [PATCH v2] nfsd: release OPEN-decoded posix ACLs via op_release

[NeilBrown]

On Mon, 01 Jun 2026, Jeff Layton wrote:
> nfsd4_decode_createhow4() calls nfsd4_decode_fattr4(), which allocates
> refcounted struct posix_acl objects via posix_acl_alloc() and stores
> them in open->op_pacl and open->op_dpacl. These pointers must be
> released once the OPEN compound finishes.
> 
> When nfsd4_decode_open_claim4() returns a non-seqid-mutating error,
> the dispatcher short-circuits before op_func runs:
> 
>     nfsd4_proc_compound()
>       opdesc->op_func == nfsd4_open_omfg
>         if (!seqid_mutating_err(ntohl(op->status)))
>             return op->status;   /* nfsd4_open() never runs */
>       opdesc->op_release(&op->u)  /* must still release op_pacl/op_dpacl */
> 
> Before this change OP_OPEN had no .op_release in nfsd4_ops[], and the
> release pair lived inside nfsd4_open() at its out_err: label. On the
> short-circuit path nfsd4_open() is never invoked, so both posix_acl
> refs leak on every malformed OPEN compound that carries valid POSIX
> ACL createhow4 attributes.
> 
> Add nfsd4_open_release() and wire it as .op_release for OP_OPEN.
> posix_acl_release() is NULL-safe, so the single release site covers
> both the normal path and the nfsd4_open_omfg short-circuit. Remove
> the matching posix_acl_release() pair from nfsd4_open()'s out_err:
> label to avoid double-releasing.
> 
> The compound loop has two encoding branches: nfsd4_encode_operation()
> for normal ops, and nfsd4_encode_replay() for v4.0 replayed ops.
> op_release was only called from nfsd4_encode_operation(), so resources
> attached to op->u leak on the replay path. Add an op_release call to
> the replay branch as well to ensure cleanup on every path.
> 
> Fixes: 5fc51dfc2eb1 ("NFSD: Add support for XDR decoding POSIX draft ACLs")
> Signed-off-by: Chris Mason <clm@xxxxxxxx>
> Reviewed-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> Changes in v2:
> - Ensure that op_release is called in the v4.0 replay case as well
> - Link to v1: https://lore.kernel.org/r/20260531-nfsd-testing-v1-0-7bfa481b0540@xxxxxxxxxx
> ---
>  fs/nfsd/nfs4proc.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index 017474cd63b5..51998d7885ae 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -681,8 +681,6 @@ nfsd4_open(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>  	nfsd4_cleanup_open_state(cstate, open);
>  	nfsd4_bump_seqid(cstate, status);
>  out_err:
> -	posix_acl_release(open->op_dpacl);
> -	posix_acl_release(open->op_pacl);
>  	return status;
>  }
>  
> @@ -704,6 +702,13 @@ static __be32 nfsd4_open_omfg(struct svc_rqst *rqstp, struct nfsd4_compound_stat
>  	return nfsd4_open(rqstp, cstate, &op->u);
>  }
>  
> +static void
> +nfsd4_open_release(union nfsd4_op_u *u)
> +{
> +	posix_acl_release(u->open.op_dpacl);
> +	posix_acl_release(u->open.op_pacl);
> +}
> +
>  /*
>   * filehandle-manipulating ops.
>   */
> @@ -3214,6 +3219,8 @@ nfsd4_proc_compound(struct svc_rqst *rqstp)
>  			op->replay = &cstate->replay_owner->so_replay;
>  			nfsd4_encode_replay(resp->xdr, op);
>  			status = op->status = op->replay->rp_status;
> +			if (op->opdesc->op_release)
> +				op->opdesc->op_release(&op->u);
>  		} else {
>  			nfsd4_encode_operation(resp, op);
>  			status = op->status;

I think this patch is good, but I think it would be even better if the
->op_release() call were moved out of nfsd4_encode_operation() and
places after this if-else.  Then there would be only one call-site in a
fairly obviously-correct place.
But:
  Reviewed-by: NeilBrown <neil@xxxxxxxxxx>
for if you just want to stick with this version.

Thanks,
NeilBrown


> @@ -3718,6 +3725,7 @@ static const struct nfsd4_operation nfsd4_ops[] = {
>  	},
>  	[OP_OPEN] = {
>  		.op_func = nfsd4_open,
> +		.op_release = nfsd4_open_release,
>  		.op_flags = OP_HANDLES_WRONGSEC | OP_MODIFIES_SOMETHING,
>  		.op_name = "OP_OPEN",
>  		.op_rsize_bop = nfsd4_open_rsize,
> 
> ---
> base-commit: 6c0004650ba248a12937ada16f9ba961b35ce2b5
> change-id: 20260531-nfsd-testing-9122bf51ce95
> 
> Best regards,
> -- 
> Jeff Layton <jlayton@xxxxxxxxxx>
> 
>