> On Sep 2, 2022, at 4:58 PM, Benjamin Coddington <bcodding@xxxxxxxxxx> wrote:
>
> Olga, does this fix it up for you? I'm testing now, but I think it might be
> a little harder for me to hit.
>
> Ben
>
> 8<------------------------------------------------
> From 6bea39a887495b1748ff3b179d6e2f3d7e552b61 Mon Sep 17 00:00:00 2001
> From: Benjamin Coddington <bcodding@xxxxxxxxxx>
> Date: Fri, 2 Sep 2022 16:49:17 -0400
> Subject: [PATCH] SUNRPC: Fix svc_tcp_sendmsg bvec offset calculation
>
> The xdr_buf's bvec member points to an array of struct bio_vec, let's
> fixup the calculation to the start of the bio_vec for non-zero
> page_base.
>
> Fixes: bad4c6eb5eaa ("SUNRPC: Fix NFS READs that start at non-page-aligned offsets")
> Signed-off-by: Benjamin Coddington <bcodding@xxxxxxxxxx>
> ---
> net/sunrpc/svcsock.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
> index 2fc98fea59b4..ecafc9c4bc5c 100644
> --- a/net/sunrpc/svcsock.c
> +++ b/net/sunrpc/svcsock.c
> @@ -1110,7 +1110,7 @@ static int svc_tcp_sendmsg(struct socket *sock, struct xdr_buf *xdr,
> unsigned int offset, len, remaining;
> struct bio_vec *bvec;
>
> - bvec = xdr->bvec + (xdr->page_base >> PAGE_SHIFT);
> + bvec = &xdr->bvec[xdr->page_base >> PAGE_SHIFT];
Color me skeptical.
I'm not sure these two expressions are different. This variety
of pointer arithmetic is used throughout the XDR layer:
net/sunrpc/xdr.c: pgto = pages + (pgto_base >> PAGE_SHIFT);
net/sunrpc/xdr.c: pgfrom = pages + (pgfrom_base >> PAGE_SHIFT);
net/sunrpc/xdr.c: pgto = pages + (pgto_base >> PAGE_SHIFT);
net/sunrpc/xdr.c: pgfrom = pages + (pgfrom_base >> PAGE_SHIFT);
net/sunrpc/xdr.c: pgto = pages + (pgbase >> PAGE_SHIFT);
net/sunrpc/xdr.c: pgfrom = pages + (pgbase >> PAGE_SHIFT);
net/sunrpc/xdr.c: page = pages + (pgbase >> PAGE_SHIFT);
net/sunrpc/xdr.c: xdr->page_ptr = buf->pages + (new >> PAGE_SHIFT);
net/sunrpc/xdr.c: ppages = buf->pages + (base >> PAGE_SHIFT);
net/sunrpc/xprtrdma/rpc_rdma.c: ppages = buf->pages + (buf->page_base >> PAGE_SHIFT);
net/sunrpc/xprtrdma/rpc_rdma.c: ppages = xdrbuf->pages + (xdrbuf->page_base >> PAGE_SHIFT);
net/sunrpc/xprtrdma/rpc_rdma.c: ppages = xdr->pages + (xdr->page_base >> PAGE_SHIFT);
net/sunrpc/xprtrdma/rpc_rdma.c: ppages = xdr->pages + (xdr->page_base >> PAGE_SHIFT);
Commit bad4c6eb5eaa is from v5.11. Wouldn't this issue have
shown up in earlier kernels? At the very least, the patch
description needs to explain why this computation is not a
problem for kernels 5.11 through 5.19.
> offset = offset_in_page(xdr->page_base);
> remaining = xdr->page_len;
> while (remaining > 0) {
> --
> 2.37.2
>
--
Chuck Lever
