net: Fix a data-race around gro_normal_batch.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2160073
Upstream Status: linux.git

commit 8db24af
Author: Kuniyuki Iwashima <kuniyu@amazon.com>
Date:   Tue Aug 23 10:46:58 2022 -0700

    net: Fix a data-race around gro_normal_batch.

    While reading gro_normal_batch, it can be changed concurrently.
    Thus, we need to add READ_ONCE() to its reader.

    Fixes: 323ebb6 ("net: use listified RX for handling GRO_NORMAL skbs")
    Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
    Acked-by: Edward Cree <ecree.xilinx@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Guillaume Nault <gnault@redhat.com>

Author: Guillaume Nault

include/net/gro.h

@@ -434,7 +434,7 @@ static inline void gro_normal_one(struct napi_struct *napi, struct sk_buff *skb,
 {
 	list_add_tail(&skb->list, &napi->rx_list);
 	napi->rx_count += segs;
-	if (napi->rx_count >= gro_normal_batch)
+	if (napi->rx_count >= READ_ONCE(gro_normal_batch))
 		gro_normal_list(napi);
 }