Received-SPF: pass (google.com: domain of linux-nfs-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 30 Jun 2022 17:12:54 -0400
From:   "J. Bruce Fields" <bfields@fieldses.org>
To:     Chuck Lever <chuck.lever@oracle.com>
Cc:     linux-nfs@vger.kernel.org, anna.schumaker@netapp.com,
        zlang@redhat.com
Subject: Re: [PATCH v1] SUNRPC: Fix READ_PLUS crasher
Message-ID: <20220630211254.GD22291@fieldses.org>
References: <165660978413.2453.15153844664543877314.stgit@klimt.1015granger.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <165660978413.2453.15153844664543877314.stgit@klimt.1015granger.net>
User-Agent: Mutt/1.5.21 (2010-09-15)
Precedence: bulk

Looks like the crash I saw no longer reproduces after that, fwiw.

--b.

On Thu, Jun 30, 2022 at 01:24:20PM -0400, Chuck Lever wrote:
> Looks like there are still cases when "space_left - frag1bytes" can
> legitimately exceed PAGE_SIZE. Ensure that xdr->end always remains
> within the current encode buffer.
> 
> Reported-by: Bruce Fields <bfields@fieldses.org>
> Reported-by: Zorro Lang <zlang@redhat.com>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216151
> Fixes: 6c254bf3b637 ("SUNRPC: Fix the calculation of xdr->end in xdr_get_next_encode_buffer()")
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
>  net/sunrpc/xdr.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Hi-
> 
> I had a few minutes yesterday afternoon to look into this one. The
> following one-liner seems to address the issue and passes my smoke
> tests with NFSv4.1/TCP and NFSv3/RDMA. Any thoughts?
> 
> 
> diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
> index f87a2d8f23a7..916659be2774 100644
> --- a/net/sunrpc/xdr.c
> +++ b/net/sunrpc/xdr.c
> @@ -987,7 +987,7 @@ static noinline __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
>  	if (space_left - nbytes >= PAGE_SIZE)
>  		xdr->end = p + PAGE_SIZE;
>  	else
> -		xdr->end = p + space_left - frag1bytes;
> +		xdr->end = p + min_t(int, space_left - frag1bytes, PAGE_SIZE);
>  
>  	xdr->buf->page_len += frag2bytes;
>  	xdr->buf->len += nbytes;
>