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[204.195.96.226]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fac10d1c78sm161360025ad.23.2024.07.06.08.01.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 06 Jul 2024 08:01:04 -0700 (PDT) Date: Sat, 6 Jul 2024 08:01:02 -0700 From: Stephen Hemminger To: Jeongjun Park Cc: jiri@resnulli.us, syzbot+705c61d60b091ef42c04@syzkaller.appspotmail.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, syzkaller-bugs@googlegroups.com Subject: Re: [PATCH net,v2] team: Fix ABBA deadlock caused by race in team_del_slave Message-ID: <20240706080102.1cccb499@hermes.local> In-Reply-To: <20240706041329.96637-1-aha310510@gmail.com> References: <000000000000ffc5d80616fea23d@google.com> <20240706041329.96637-1-aha310510@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Sat, 6 Jul 2024 13:13:29 +0900 Jeongjun Park wrote: > CPU0 CPU1 > ---- ---- > lock(&rdev->wiphy.mtx); > lock(team->team_lock_key#4); > lock(&rdev->wiphy.mtx); > lock(team->team_lock_key#4); > > Deadlock occurs due to the above scenario. Therefore, you can prevent > deadlock by briefly releasing the lock before calling dev_open() in > team_port_add() and locking it again after it returns. > > Reported-and-tested-by: syzbot+705c61d60b091ef42c04@syzkaller.appspotmail.com > Fixes: 3d249d4ca7d0 ("net: introduce ethernet teaming device") > Signed-off-by: Jeongjun Park > --- But if you drop the lock the actual data structures might have changed. Usually not a good idea,