Re: [PATCH 1/2] nfsd4: Handle the NFSv4 READDIR 'dircount' hint being zero

[Chuck Lever III <chuck.lever@oracle.com>]

> On Sep 30, 2021, at 3:44 PM, trondmy@kernel.org wrote:
> 
> From: Trond Myklebust <trond.myklebust@hammerspace.com>
> 
> RFC3530 notes that the 'dircount' field may be zero, in which case the
> recommendation is to ignore it, and only enforce the 'maxcount' field.
> In RFC5661, this recommendation to ignore a zero valued field becomes a
> requirement.
> 
> Fixes: aee377644146 ("nfsd4: fix rd_dircount enforcement")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Pulled into the next 5.15-rc for NFSD. Thanks!


> ---
> fs/nfsd/nfs4xdr.c | 19 +++++++++++--------
> 1 file changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 7abeccb975b2..cf030ebe2827 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -3544,15 +3544,18 @@ nfsd4_encode_dirent(void *ccdv, const char *name, int namlen,
> 		goto fail;
> 	cd->rd_maxcount -= entry_bytes;
> 	/*
> -	 * RFC 3530 14.2.24 describes rd_dircount as only a "hint", so
> -	 * let's always let through the first entry, at least:
> +	 * RFC 3530 14.2.24 describes rd_dircount as only a "hint", and
> +	 * notes that it could be zero. If it is zero, then the server
> +	 * should enforce only the rd_maxcount value.
> 	 */
> -	if (!cd->rd_dircount)
> -		goto fail;
> -	name_and_cookie = 4 + 4 * XDR_QUADLEN(namlen) + 8;
> -	if (name_and_cookie > cd->rd_dircount && cd->cookie_offset)
> -		goto fail;
> -	cd->rd_dircount -= min(cd->rd_dircount, name_and_cookie);
> +	if (cd->rd_dircount) {
> +		name_and_cookie = 4 + 4 * XDR_QUADLEN(namlen) + 8;
> +		if (name_and_cookie > cd->rd_dircount && cd->cookie_offset)
> +			goto fail;
> +		cd->rd_dircount -= min(cd->rd_dircount, name_and_cookie);
> +		if (!cd->rd_dircount)
> +			cd->rd_maxcount = 0;
> +	}
> 
> 	cd->cookie_offset = cookie_offset;
> skip_entry:
> -- 
> 2.31.1
> 

--
Chuck Lever