netdev - [PATCH bpf] xdp: Handle MEM_TYPE_XSK_BUFF_POOL correctly in xdp_return

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Date:   Fri, 27 Nov 2020 18:17:26 +0100
From:   Björn Töpel <bjorn.topel@...il.com>
To:     ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Cc:     Björn Töpel <bjorn.topel@...el.com>,
        jonathan.lemon@...il.com, magnus.karlsson@...el.com,
        maximmi@...dia.com
Subject: [PATCH bpf] xdp: Handle MEM_TYPE_XSK_BUFF_POOL correctly in xdp_return_buff()

From: Björn Töpel <bjorn.topel@...el.com>

It turns out that it does exist a path where xdp_return_buff() is
being passed an XDP buffer of type MEM_TYPE_XSK_BUFF_POOL. This path
is when AF_XDP zero-copy mode is enabled, and a buffer is redirected
to a DEVMAP with an attached XDP program that drops the buffer.

This change simply puts the handling of MEM_TYPE_XSK_BUFF_POOL back
into xdp_return_buff().

Reported-by: Maxim Mikityanskiy <maximmi@...dia.com>
Fixes: 82c41671ca4f ("xdp: Simplify xdp_return_{frame, frame_rx_napi, buff}")
Signed-off-by: Björn Töpel <bjorn.topel@...el.com>
---
 net/core/xdp.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/net/core/xdp.c b/net/core/xdp.c
index 48aba933a5a8..491ad569a79c 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -335,11 +335,10 @@ EXPORT_SYMBOL_GPL(xdp_rxq_info_reg_mem_model);
  * scenarios (e.g. queue full), it is possible to return the xdp_frame
  * while still leveraging this protection.  The @napi_direct boolean
  * is used for those calls sites.  Thus, allowing for faster recycling
- * of xdp_frames/pages in those cases. This path is never used by the
- * MEM_TYPE_XSK_BUFF_POOL memory type, so it's explicitly not part of
- * the switch-statement.
+ * of xdp_frames/pages in those cases.
  */
-static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct)
+static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct,
+			 struct xdp_buff *xdp)
 {
 	struct xdp_mem_allocator *xa;
 	struct page *page;
@@ -361,6 +360,10 @@ static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct)
 		page = virt_to_page(data); /* Assumes order0 page*/
 		put_page(page);
 		break;
+	case MEM_TYPE_XSK_BUFF_POOL:
+		/* NB! Only valid from an xdp_buff! */
+		xsk_buff_free(xdp);
+		break;
 	default:
 		/* Not possible, checked in xdp_rxq_info_reg_mem_model() */
 		WARN(1, "Incorrect XDP memory type (%d) usage", mem->type);
@@ -370,19 +373,19 @@ static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct)
 
 void xdp_return_frame(struct xdp_frame *xdpf)
 {
-	__xdp_return(xdpf->data, &xdpf->mem, false);
+	__xdp_return(xdpf->data, &xdpf->mem, false, NULL);
 }
 EXPORT_SYMBOL_GPL(xdp_return_frame);
 
 void xdp_return_frame_rx_napi(struct xdp_frame *xdpf)
 {
-	__xdp_return(xdpf->data, &xdpf->mem, true);
+	__xdp_return(xdpf->data, &xdpf->mem, true, NULL);
 }
 EXPORT_SYMBOL_GPL(xdp_return_frame_rx_napi);
 
 void xdp_return_buff(struct xdp_buff *xdp)
 {
-	__xdp_return(xdp->data, &xdp->rxq->mem, true);
+	__xdp_return(xdp->data, &xdp->rxq->mem, true, xdp);
 }
 
 /* Only called for MEM_TYPE_PAGE_POOL see xdp.h */

base-commit: 9a44bc9449cfe7e39dbadf537ff669fb007a9e63
-- 
2.27.0