[PATCH 5.15 055/244] SUNRPC: Reinitialise the backchannel request buffers before reuse

Greg Kroah-Hartman
2022-08-23T09:49:32Z

From: Trond Myklebust <trond.myklebust@hammerspace.com>

commit 6622e3a73112fc336c1c2c582428fb5ef18e456a upstream.

When we're reusing the backchannel requests instead of freeing them,
then we should reinitialise any values of the send/receive xdr_bufs so
that they reflect the available space.

Fixes: 0d2a970d0ae5 ("SUNRPC: Fix a backchannel race")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sunrpc/backchannel_rqst.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

--- a/net/sunrpc/backchannel_rqst.c
+++ b/net/sunrpc/backchannel_rqst.c
@@ -64,6 +64,17 @@ static void xprt_free_allocation(struct
kfree(req);
}

+static void xprt_bc_reinit_xdr_buf(struct xdr_buf *buf)
+{
+ buf->head[0].iov_len = PAGE_SIZE;
+ buf->tail[0].iov_len = 0;
+ buf->pages = NULL;
+ buf->page_len = 0;
+ buf->flags = 0;
+ buf->len = 0;
+ buf->buflen = PAGE_SIZE;
+}
+
static int xprt_alloc_xdr_buf(struct xdr_buf *buf, gfp_t gfp_flags)
{
struct page *page;
@@ -292,6 +303,9 @@ void xprt_free_bc_rqst(struct rpc_rqst *
*/
spin_lock_bh(&xprt->bc_pa_lock);
if (xprt_need_to_requeue(xprt)) {
+ xprt_bc_reinit_xdr_buf(&req->rq_snd_buf);
+ xprt_bc_reinit_xdr_buf(&req->rq_rcv_buf);
+ req->rq_rcv_buf.len = PAGE_SIZE;
list_add_tail(&req->rq_bc_pa_list, &xprt->bc_pa_list);
xprt->bc_alloc_count++;
atomic_inc(&xprt->bc_slot_count);