neighbour: fix unaligned access to pneigh_entry

commit ed779fe4c9b5a20b4ab4fd6f3e19807445bb78c7 upstream.

After the blamed commit, the member key is longer 4-byte aligned. On
platforms that do not support unaligned access, e.g., MIPS32R2 with
unaligned_action set to 1, this will trigger a crash when accessing
an IPv6 pneigh_entry, as the key is cast to an in6_addr pointer.

Change the type of the key to u32 to make it aligned.

Fixes: 62dd93181aaa ("[IPV6] NDISC: Set per-entry is_router flag in Proxy NA.")
Signed-off-by: Qingfang DENG <qingfang.deng@siflower.com.cn>
Link: https://lore.kernel.org/r/20230601015432.159066-1-dqfext@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit f451d1a013fd585cbf70a65ca6b9cf3548bb039f)
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
diff --git a/include/net/neighbour.h b/include/net/neighbour.h
index cb4c313..240d08f 100644
--- a/include/net/neighbour.h
+++ b/include/net/neighbour.h
@@ -172,7 +172,7 @@
 	possible_net_t		net;
 	struct net_device	*dev;
 	u8			flags;
-	u8			key[0];
+	u32			key[0];
 };
 
 /*