llc: Don't drop packet from non-root netns.

stable inclusion
from stable-v5.10.188
commit a6f1988780a7c9e5f54a1d6d363db99e850106fc
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8KYFP

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a6f1988780a7c9e5f54a1d6d363db99e850106fc



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[ Upstream commit 6631463b ]

Now these upper layer protocol handlers can be called from llc_rcv()
as sap->rcv_func(), which is registered by llc_sap_open().

  * function which is passed to register_8022_client()
    -> no in-kernel user calls register_8022_client().

  * snap_rcv()
    `- proto->rcvfunc() : registered by register_snap_client()
       -> aarp_rcv() and atalk_rcv() drop packets from non-root netns

  * stp_pdu_rcv()
    `- garp_protos[]->rcv() : registered by stp_proto_register()
       -> garp_pdu_rcv() and br_stp_rcv() are netns-aware

So, we can safely remove the netns restriction in llc_rcv().

Fixes: e730c155 ("[NET]: Make packet reception network namespace safe")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>