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([2a0d:3344:5521:6b10:58fd:68f:7756:389d]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-493eb70a677sm39467095e9.8.2026.07.09.01.16.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 09 Jul 2026 01:16:49 -0700 (PDT) Message-ID: <695fc2fb-606e-4d5a-a4d6-41ba5d1cfadb@redhat.com> Date: Thu, 9 Jul 2026 10:16:48 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] net: erspan: set lltx to avoid sch_direct_xmit deadlock To: Yun Zhou , dsahern@kernel.org, idosch@nvidia.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, horms@kernel.org Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260709065631.3488067-1-yun.zhou@windriver.com> From: Paolo Abeni Content-Language: en-US In-Reply-To: <20260709065631.3488067-1-yun.zhou@windriver.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/9/26 8:56 AM, Yun Zhou wrote: > erspan_xmit() re-enters the network stack via ip_tunnel_xmit(), causing > nested acquisition of _xmit_lock on the underlay device while already > holding the ERSPAN device's _xmit_lock. Both are ARPHRD_ETHER and share > the same lockdep class, creating an ABBA deadlock: > > sch_direct_xmit [lock erspan] -> erspan_xmit -> ip_tunnel_xmit -> > ip_output -> __dev_queue_xmit -> sch_direct_xmit [lock underlay] > > Set dev->lltx = true so HARD_TX_LOCK() skips the spinlock for ERSPAN. > This is safe as erspan_xmit() has no shared mutable state: o_seqno is > atomic, stats use atomic_long_inc, and dst_cache is per-CPU. GRETAP, > the sibling device with identical xmit structure, already sets lltx. > > Closes: https://syzkaller.appspot.com/bug?extid=9bda1b9fbb7fbdf9b62b > Reported-by: syzbot+9bda1b9fbb7fbdf9b62b@syzkaller.appspotmail.com > Fixes: 84e54fe0a5ea ("gre: introduce native tunnel support for ERSPAN") > Signed-off-by: Yun Zhou So this is actually a v2 of: 20260630183702.170798-2-hemendranaik@gmail.com/20260630183702.170798-2-hemendranaik@gmail.com/ right? please have a look at: https://elixir.bootlin.com/linux/v7.1/source/Documentation/process/maintainer-netdev.rst#L434 any kind of re-submission matters, no matter how trivial is the reason. /P