netdev - [PATCH net] netdev-genl: fix error codes when outputting XDP features

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Date: Thu, 13 Jun 2024 14:30:44 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org,
	edumazet@...gle.com,
	pabeni@...hat.com,
	Jakub Kicinski <kuba@...nel.org>,
	hawk@...nel.org,
	amritha.nambiar@...el.com,
	sridhar.samudrala@...el.com,
	alardam@...il.com,
	lorenzo@...nel.org,
	memxor@...il.com
Subject: [PATCH net] netdev-genl: fix error codes when outputting XDP features

-EINVAL will interrupt the dump. The correct error to return
if we have more data to dump is -EMSGSIZE.

Discovered by doing:

  for i in `seq 80`; do ip link add type veth; done
  ./cli.py --dbg-small-recv 5300 --spec netdev.yaml --dump dev-get >> /dev/null
  [...]
     nl_len = 64 (48) nl_flags = 0x0 nl_type = 19
     nl_len = 20 (4) nl_flags = 0x2 nl_type = 3
  	error: -22

Fixes: d3d854fd6a1d ("netdev-genl: create a simple family for netdev stuff")
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
CC: hawk@...nel.org
CC: amritha.nambiar@...el.com
CC: sridhar.samudrala@...el.com
CC: alardam@...il.com
CC: lorenzo@...nel.org
CC: memxor@...il.com
---
 net/core/netdev-genl.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index 1f6ae6379e0f..05f9515d2c05 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -59,22 +59,22 @@ XDP_METADATA_KFUNC_xxx
 	    nla_put_u64_64bit(rsp, NETDEV_A_DEV_XDP_RX_METADATA_FEATURES,
 			      xdp_rx_meta, NETDEV_A_DEV_PAD) ||
 	    nla_put_u64_64bit(rsp, NETDEV_A_DEV_XSK_FEATURES,
-			      xsk_features, NETDEV_A_DEV_PAD)) {
-		genlmsg_cancel(rsp, hdr);
-		return -EINVAL;
-	}
+			      xsk_features, NETDEV_A_DEV_PAD))
+		goto err_cancel_msg;
 
 	if (netdev->xdp_features & NETDEV_XDP_ACT_XSK_ZEROCOPY) {
 		if (nla_put_u32(rsp, NETDEV_A_DEV_XDP_ZC_MAX_SEGS,
-				netdev->xdp_zc_max_segs)) {
-			genlmsg_cancel(rsp, hdr);
-			return -EINVAL;
-		}
+				netdev->xdp_zc_max_segs))
+			goto err_cancel_msg;
 	}
 
 	genlmsg_end(rsp, hdr);
 
 	return 0;
+
+err_cancel_msg:
+	genlmsg_cancel(rsp, hdr);
+	return -EMSGSIZE;
 }
 
 static void
-- 
2.45.2