netdev - [PATCH bpf] xdp: check device pointer before clearing

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Message-Id: <20190607172732.4710-1-i.maximets@samsung.com>
Date:   Fri,  7 Jun 2019 20:27:32 +0300
From:   Ilya Maximets <i.maximets@...sung.com>
To:     netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
        xdp-newbies@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Björn Töpel <bjorn.topel@...el.com>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Ilya Maximets <i.maximets@...sung.com>
Subject: [PATCH bpf] xdp: check device pointer before clearing

We should not call 'ndo_bpf()' or 'dev_put()' with NULL argument.

Fixes: c9b47cc1fabc ("xsk: fix bug when trying to use both copy and zero-copy on one queue id")
Signed-off-by: Ilya Maximets <i.maximets@...sung.com>
---

I'm not sure if this fixes any real NULL pointer dereference, but code
is not consistent anyway and should be fixed.

 net/xdp/xdp_umem.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
index 2b18223e7eb8..9c6de4f114f8 100644
--- a/net/xdp/xdp_umem.c
+++ b/net/xdp/xdp_umem.c
@@ -143,6 +143,9 @@ static void xdp_umem_clear_dev(struct xdp_umem *umem)
 	struct netdev_bpf bpf;
 	int err;
 
+	if (!umem->dev)
+		return;
+
 	if (umem->zc) {
 		bpf.command = XDP_SETUP_XSK_UMEM;
 		bpf.xsk.umem = NULL;
@@ -156,11 +159,9 @@ static void xdp_umem_clear_dev(struct xdp_umem *umem)
 			WARN(1, "failed to disable umem!\n");
 	}
 
-	if (umem->dev) {
-		rtnl_lock();
-		xdp_clear_umem_at_qid(umem->dev, umem->queue_id);
-		rtnl_unlock();
-	}
+	rtnl_lock();
+	xdp_clear_umem_at_qid(umem->dev, umem->queue_id);
+	rtnl_unlock();
 
 	if (umem->zc) {
 		dev_put(umem->dev);
-- 
2.17.1