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[95.169.12.199]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-34145727589sm19752996eec.23.2026.09.27.00.45.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 27 Sep 2026 00:45:28 -0700 (PDT) From: Chengfeng Ye To: "D. Wythe" , Dust Li , Sidraya Jayagond , Mahanta Jambigi , Tony Lu , Wen Gu , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Karsten Graul , Ursula Braun Cc: linux-rdma@vger.kernel.org, linux-s390@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Chengfeng Ye , stable@vger.kernel.org Subject: [PATCH net] net/smc: serialize link group free work scheduling Date: Sun, 27 Sep 2026 15:45:20 +0800 Message-ID: <20260927074520.3694663-1-nicoyip.dev@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit smc_lgr_schedule_free_work() checks lgr->freeing without the link group list lock held by the teardown paths. A concurrent smc_lgr_free_work() can set freeing and cancel the delayed work between that check and mod_delayed_work(), leaving a timer pending on a freed link group: CPU 0 (smc_conn_free) CPU 1 (smc_lgr_free_work) observe lgr->freeing == 0 set lgr->freeing under lgr_lock cancel_delayed_work() smc_lgr_free(): drop lgr reference mod_delayed_work() smc_lgr_put(): drop last reference and free lgr When the timer expires, the timer core accesses the freed memory. KASAN reported: BUG: KASAN: use-after-free in __run_timers+0x86d/0x8d0 Write of size 8 at addr ffff8881186902a8 by task swapper/2/0 Call Trace: __run_timers+0x86d/0x8d0 timer_expire_remote+0xd3/0x120 tmigr_handle_remote_up+0x4f4/0xab0 __walk_groups_from+0x40/0x150 tmigr_handle_remote+0x229/0x2c0 run_timer_softirq+0x1f5/0x250 handle_softirqs+0x18d/0x5b0 Hold the existing link group list lock across the freeing check and mod_delayed_work(). Rearming then either precedes the freeing transition and is caught by the subsequent cancellation, or sees freeing set and is skipped. smc_conn_free() retains its link group reference until after scheduling, keeping the group alive while acquiring the lock. Fixes: 8e316b9e7260 ("net/smc: improve link group freeing") Cc: stable@vger.kernel.org Signed-off-by: Chengfeng Ye --- net/smc/smc_core.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c index 9974149659c2..8feb486ada56 100644 --- a/net/smc/smc_core.c +++ b/net/smc/smc_core.c @@ -80,6 +80,10 @@ static void smc_ibdev_cnt_dec(struct smc_link *lnk) static void smc_lgr_schedule_free_work(struct smc_link_group *lgr) { + spinlock_t *lgr_lock; /* protects lgr->freeing */ + + smc_lgr_list_head(lgr, &lgr_lock); + spin_lock_bh(lgr_lock); /* client link group creation always follows the server link group * creation. For client use a somewhat higher removal delay time, * otherwise there is a risk of out-of-sync link groups. @@ -90,6 +94,7 @@ static void smc_lgr_schedule_free_work(struct smc_link_group *lgr) SMC_LGR_FREE_DELAY_CLNT : SMC_LGR_FREE_DELAY_SERV); } + spin_unlock_bh(lgr_lock); } /* Register connection's alert token in our lookup structure. -- 2.43.0