Re: [PATCH 1/1] NFSv4: include bitmap in nfsv4 get acl data

[Jeff Layton <jlayton@redhat.com>]

On Sat,  5 Nov 2011 03:21:52 -0400
andros@netapp.com wrote:

> From: Andy Adamson <andros@netapp.com>
> 
> The NFSv4 bitmap size is unbounded: a server can return an arbitrary
> sized bitmap in an FATTR4_WORD0_ACL request.  Replace using the
> nfs4_fattr_bitmap_maxsz as a guess to the maximum bitmask returned by a server
> with the inclusion of the bitmap (xdr length plus bitmasks) and the acl data
> xdr length to the (cached) acl page data.
> 
> This is a general solution to commit e5012d1f "NFSv4.1: update
> nfs4_fattr_bitmap_maxsz" and fixes hitting a BUG_ON in xdr_shrink_bufhead
> when getting ACLs.
> 
> Cc:stable@kernel.org
> Signed-off-by: Andy Adamson <andros@netapp.com>
> ---
>  fs/nfs/nfs4proc.c |   20 ++++++++++++++++++--
>  fs/nfs/nfs4xdr.c  |   15 ++++++++++++---
>  2 files changed, 30 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index deb88d9..97014dd 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -3671,6 +3671,22 @@ static void nfs4_zap_acl_attr(struct inode *inode)
>  	nfs4_set_cached_acl(inode, NULL);
>  }
>  
> +/*
> + * The bitmap xdr length, bitmasks, and the attr xdr length are stored in
> + * the acl cache to handle variable length bitmasks. Just copy the acl data.
> + */
> +static void nfs4_copy_acl(char *buf, char *acl_data, size_t acl_len)
> +{
> +	__be32 *q, *p = (__be32 *)acl_data;
> +	int32_t len;
> +
> +	len = be32_to_cpup(p); /* number of bitmasks */
> +	len += 2;  /* add words for bitmap and attr xdr len */
> +	q = p + len;
> +	len = len << 2; /* convert to bytes for acl_len math */
> +	memcpy(buf, (char *)q, acl_len - len);
> +}
> +
>  static inline ssize_t nfs4_read_cached_acl(struct inode *inode, char *buf, size_t buflen)
>  {
>  	struct nfs_inode *nfsi = NFS_I(inode);
> @@ -3688,7 +3704,7 @@ static inline ssize_t nfs4_read_cached_acl(struct inode *inode, char *buf, size_
>  	ret = -ERANGE; /* see getxattr(2) man page */
>  	if (acl->len > buflen)
>  		goto out;
> -	memcpy(buf, acl->data, acl->len);
> +	nfs4_copy_acl(buf, acl->data, acl->len);
>  out_len:
>  	ret = acl->len;
>  out:
> @@ -3763,7 +3779,7 @@ static ssize_t __nfs4_get_acl_uncached(struct inode *inode, void *buf, size_t bu
>  		if (res.acl_len > buflen)
>  			goto out_free;
>  		if (localpage)
> -			memcpy(buf, resp_buf, res.acl_len);
> +			nfs4_copy_acl(buf, resp_buf, res.acl_len);
>  	}
>  	ret = res.acl_len;
>  out_free:
> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
> index f9fd96d..9c07380 100644
> --- a/fs/nfs/nfs4xdr.c
> +++ b/fs/nfs/nfs4xdr.c
> @@ -2513,7 +2513,7 @@ static void nfs4_xdr_enc_getacl(struct rpc_rqst *req, struct xdr_stream *xdr,
>  	encode_compound_hdr(xdr, req, &hdr);
>  	encode_sequence(xdr, &args->seq_args, &hdr);
>  	encode_putfh(xdr, args->fh, &hdr);
> -	replen = hdr.replen + op_decode_hdr_maxsz + nfs4_fattr_bitmap_maxsz + 1;
> +	replen = hdr.replen + op_decode_hdr_maxsz + 1;
>  	encode_getattr_two(xdr, FATTR4_WORD0_ACL, 0, &hdr);
>  
>  	xdr_inline_pages(&req->rq_rcv_buf, replen << 2,
> @@ -4955,7 +4955,7 @@ decode_restorefh(struct xdr_stream *xdr)
>  static int decode_getacl(struct xdr_stream *xdr, struct rpc_rqst *req,
>  		size_t *acl_len)
>  {
> -	__be32 *savep;
> +	__be32 *savep, *bm_p;
>  	uint32_t attrlen,
>  		 bitmap[3] = {0};
>  	struct kvec *iov = req->rq_rcv_buf.head;
> @@ -4964,6 +4964,7 @@ static int decode_getacl(struct xdr_stream *xdr, struct rpc_rqst *req,
>  	*acl_len = 0;
>  	if ((status = decode_op_hdr(xdr, OP_GETATTR)) != 0)
>  		goto out;
> +	bm_p = xdr->p;
>  	if ((status = decode_attr_bitmap(xdr, bitmap)) != 0)
>  		goto out;
>  	if ((status = decode_attr_length(xdr, &attrlen, &savep)) != 0)
> @@ -4972,12 +4973,20 @@ static int decode_getacl(struct xdr_stream *xdr, struct rpc_rqst *req,
>  	if (unlikely(bitmap[0] & (FATTR4_WORD0_ACL - 1U)))
>  		return -EIO;
>  	if (likely(bitmap[0] & FATTR4_WORD0_ACL)) {
> -		size_t hdrlen;
> +		size_t hdrlen, len;
>  		u32 recvd;
>  
> +		/*The bitmap (xdr len + bitmasks) and the attr xdr len words
> +		 * are stored with the acl data to handle the problem of
> +		 * variable length bitmasks.*/
> +		xdr->p = bm_p;
> +		len = be32_to_cpup(bm_p);
> +		len += 2; /* add bitmap and attr xdr len words */
> +
>  		/* We ignore &savep and don't do consistency checks on
>  		 * the attr length.  Let userspace figure it out.... */
>  		hdrlen = (u8 *)xdr->p - (u8 *)iov->iov_base;
> +		attrlen += len << 2; /* attrlen is in bytes */
>  		recvd = req->rq_rcv_buf.len - hdrlen;
>  		if (attrlen > recvd) {
>  			dprintk("NFS: server cheating in getattr"

Nice work... I think this looks good:

Acked-by: Jeff Layton <jlayton@redhat.com>