[PATCH net-next] net: report netlink extack only if set

[Willem de Bruijn]

From: Willem de Bruijn <will...@google.com>

Initialize extack in dev_set_mtu and report only if set.

Fixes: 7a4c53bee332 ("net: report invalid mtu value via netlink extack")
Reported-by: syzbot <syzkal...@googlegroups.com>
Signed-off-by: Willem de Bruijn <will...@google.com>
---
 net/core/dev.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 36e994519488e..1d0122a766019 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -7580,11 +7580,11 @@ int dev_set_mtu_ext(struct net_device *dev, int new_mtu,
 
 int dev_set_mtu(struct net_device *dev, int new_mtu)
 {
-       struct netlink_ext_ack extack;
+       struct netlink_ext_ack extack = {};
        int err;
 
        err = dev_set_mtu_ext(dev, new_mtu, &extack);
-       if (err)
+       if (err && extack._msg)
                net_err_ratelimited("%s: %s\n", dev->name, extack._msg);
        return err;
 }
-- 
2.18.0.597.ga71716f1ad-goog