From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=115.124.30.99 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793100340; b=SYXy8mmwpJhx0SxQ2w/FAUKhWXXUxRBO8zVyg3UXajAYXqsBk5NFmc58ktaL/tV77sWX gKanIUejjHcCmL0gWeSrQ0yyVZs09HLLb/mrd9QOANoiX31OlwDgmoxY7yeC2n7L8LTDU W4tyuwF1WeHTL0Nll+Ka+VcwM69UVObpeMoGxI0ow0otk4P/nH2UfbA9Lf4S7h3X4+Hf2 yenk5ImoQKL1G9sKGXyHGHyOTXvbGbzzy1eZJ/1kgaeRw6uG5BEidYFa7HjAMTRANWWxE Ebux2YsdLx4txK2QSTfbK5HvENRXBvlZOcT5J/B+SpYhWkBWNat2zu2H3xRuoPLZ5mQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793100340; h=DMARC-Filter:DKIM-Signature:X-Alimail-AntiSpam:Received:Date:From:To: Cc:Subject:Message-ID:Reply-To:References:MIME-Version:Content-Type: Content-Disposition:Content-Transfer-Encoding:In-Reply-To; bh=gNaOmLJ54pQ1sRvF3/VAAAqJujB8QNCU6C1ZtrVopkw=; b=EMqVR6ZhD95YpRI/gBrTH1uLQz5Xd/XNomV7ciO82MGAYLqDW8LDpjZCXuW8UFo/YQaZ DwB6FJO1Hey51CVqNEO/cGAe3TidplB8CD68v/8gdIHwEBej/kxpoV9Do3Mc1F0V0twUw qKkPXrwVVYenaU/+D2ABB5UGc7kXOQP1qqlJHBrsGc1pKRbLotgPYk+p9LqVFkFiRAFu/ iIAwHx5aEOXS1oSbBxLZwyDfKaVGBiXeaNTryt6YpaHFd3C4/cX+Eel+oEF5DYTBdDLg/ IkO00hJfwY9uSNFjuFoBEraS0k2HWZjE83VjgBYBYqoxa9Q9ppw+Eopwo4ie7LTqqaQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass header.d=linux.alibaba.com header.i=@linux.alibaba.com header.a=rsa-sha256 header.s=default header.b=sAX4aqcl; arc=none smtp.remote-ip=115.124.30.99 Received: from out30-99.freemail.mail.aliyun.com (out30-99.freemail.mail.aliyun.com [115.124.30.99]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 632C5606A31B; Tue, 27 Oct 2026 11:25:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 632C5606A31B Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.a=rsa-sha256 header.s=default header.b=sAX4aqcl DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1793100333; h=Date:From:To:Subject:Message-ID:MIME-Version:Content-Type; bh=gNaOmLJ54pQ1sRvF3/VAAAqJujB8QNCU6C1ZtrVopkw=; b=sAX4aqclhG3gavWkBfeM4ig7Ez5nXLhBK2ooNXshYWsylEz1TNc8t029AnELw7ZPCKsV+2zTNTrfmzKySDJTRSMQ/GtB8oyw5NBnYD2mrTuq2vM5BRwp3/bYCvyV8ixA+l2ARJ+lIyQX+RQ/qvFrujNGl97FPrcvtp2WCVdorPU= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R541e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033032089153;MF=dust.li@linux.alibaba.com;NM=1;PH=DS;RN=16;SR=0;TI=SMTPD_---0XDdfyuc_1793100331; Received: from localhost(mailfrom:dust.li@linux.alibaba.com fp:SMTPD_---0XDdfyuc_1793100331 cluster:ay36) by smtp.aliyun-inc.com; Tue, 27 Oct 2026 19:25:32 +0800 Date: Tue, 27 Oct 2026 19:25:31 +0800 From: Dust Li To: Chengfeng Ye Cc: alibuda@linux.alibaba.com, sidraya@linux.ibm.com, mjambigi@linux.ibm.com, davem@davemloft.net, edumazet@kernel.org, kuba@kernel.org, pabeni@redhat.com, tonylu@linux.alibaba.com, guwen@linux.alibaba.com, horms@kernel.org, linux-rdma@vger.kernel.org, linux-s390@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH net v3 2/3] net/smc: serialize early link group cleanup with termination Message-ID: Reply-To: dust.li@linux.alibaba.com References: <20261013091716.1210420-1-nicoyip.dev@gmail.com> <20261013091716.1210420-3-nicoyip.dev@gmail.com> X-Mailing-List: netdev@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On 2026-10-27 19:16:26, Chengfeng Ye wrote: >Hi Dust, > >Sorry for the late reply. > >On Wed, Oct 21, 2026 at 8:13 PM Dust Li wrote: >> >> On 2026-10-13 17:17:15, Chengfeng Ye wrote: >> >smc_lgr_cleanup_early() enters __smc_lgr_terminate() even when another >> >teardown path has already claimed lgr->freeing. Both callers can observe >> >lgr->terminating clear before either sets it, then tear down the same >> >link group, causing use-after-free and duplicate resource release. >> > >> > BUG: KASAN: use-after-free in __smc_lgr_terminate+0x393/0x3a0 >> > Write of size 1 at addr ffff8880bf2c0300 by task poc/106 >> > Call Trace: >> > __smc_lgr_terminate+0x393/0x3a0 >> > __smc_connect+0x2e3d/0x4930 >> > smc_connect+0x42c/0x580 >> > __sys_connect+0xfc/0x130 >> > __x64_sys_connect+0x6d/0xb0 >> > >> >Check freeing under the link group list lock before unlinking the group >> >or entering termination. The existing locked freeing transition then >> >claims exclusive teardown ownership; an early cleanup that loses the >> >claim leaves teardown to the existing owner and does not remove the group >> >from a device teardown's private list. >> > >> >Keep a temporary link group reference across smc_conn_free() and early >> >cleanup in smc_conn_abort(). Once the connection is unregistered, a >> >termination worker can finish without taking its socket lock. The extra >> >reference keeps the allocation alive until the ownership check returns. >> > >> >A new group is published before its first connection is registered. Hold >> >it before publication until registration or failed-registration cleanup >> >finishes. The reference keeps the allocation alive, but teardown can still >> >destroy the group's resources before registration. Take the list lock >> >around the freeing check and first registration, nesting conns_lock as in >> >the reuse path. Reject a group already claimed for teardown and clear >> >conn->lgr, since that connection never acquired a group reference. >> > >> >On success, acquire the connection reference before dropping the temporary >> >hold. A later terminator sees the registered connection and must acquire >> >its socket lock before removing it. On failure, keep the temporary hold >> >through early cleanup and then release it. Reused groups retain their >> >existing reference protocol. >> > >> >This depends on "net/smc: serialize link group free work scheduling" for >> >the standalone freeing bool and the locked early-cleanup transition. >> > >> >Fixes: f9aab6f2ce57 ("net/smc: immediate freeing in smc_lgr_cleanup_early()") >> >Cc: stable@vger.kernel.org >> >Assisted-by: GPT-6.1-Sol >> >Signed-off-by: Chengfeng Ye >> >--- >> >Changes in v3: >> >- Serialize first registration with the teardown claim under the group list >> > lock, nesting conns_lock in the same order as connection reuse. >> >- Reject groups already being freed and clear conn->lgr on that path. >> >- Document the scheduling fix prerequisite in the permanent commit message. >> > >> >Changes in v2: >> >- Pin newly created link groups before publication, covering the >> > registration failure handoff to early cleanup. Drop the temporary hold >> > after cleanup on failure, or after the connection hold on success. >> >- Send after the free-work scheduling fix and reuse its standalone >> > freeing bool and locked early-cleanup transition. >> >- Pin the link group across the smc_conn_abort() early-cleanup ownership >> > check. >> > >> >v1: https://lore.kernel.org/r/20260927063607.3691520-1-nicoyip.dev@gmail.com/ >> > >> >v2: https://lore.kernel.org/r/20261003183237.2284245-3-nicoyip.dev@gmail.com/ >> > >> > net/smc/af_smc.c | 8 ++++++-- >> > net/smc/smc_core.c | 21 ++++++++++++++++++--- >> > 2 files changed, 24 insertions(+), 5 deletions(-) >> > >> >diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c >> >index e9f93b3ab435..97b0a0b51066 100644 >> >--- a/net/smc/af_smc.c >> >+++ b/net/smc/af_smc.c >> >@@ -1011,12 +1011,16 @@ static void smc_conn_abort(struct smc_sock *smc, int local_first) >> > struct smc_link_group *lgr = conn->lgr; >> > bool lgr_valid = false; >> > >> >- if (smc_conn_lgr_valid(conn)) >> >+ if (local_first && smc_conn_lgr_valid(conn)) { >> > lgr_valid = true; >> >+ smc_lgr_hold(lgr); >> >+ } >> > >> > smc_conn_free(conn); >> >- if (local_first && lgr_valid) >> >+ if (lgr_valid) { >> > smc_lgr_cleanup_early(lgr); >> >+ smc_lgr_put(lgr); >> >+ } >> > } >> > >> > /* check if there is a rdma device available for this connection. */ >> >diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c >> >index 660cd41ec720..c1bb284c4233 100644 >> >--- a/net/smc/smc_core.c >> >+++ b/net/smc/smc_core.c >> >@@ -693,6 +693,10 @@ void smc_lgr_cleanup_early(struct smc_link_group *lgr) >> > >> > smc_lgr_list_head(lgr, &lgr_lock); >> > spin_lock_bh(lgr_lock); >> >+ if (lgr->freeing) { >> >+ spin_unlock_bh(lgr_lock); >> >+ return; >> >+ } >> > /* do not use this link group for new connections */ >> > if (!list_empty(&lgr->list)) >> > list_del_init(&lgr->list); >> >@@ -999,6 +1003,7 @@ static int smc_lgr_create(struct smc_sock *smc, struct smc_init_info *ini) >> > lgr->buf_type = lgr->net->smc.sysctl_smcr_buf_type; >> > atomic_inc(&lgr_cnt); >> > } >> >+ smc_lgr_hold(lgr); /* lgr_put in smc_conn_create() */ >> > smc->conn.lgr = lgr; >> > spin_lock_bh(lgr_lock); >> > list_add_tail(&lgr->list, lgr_list); >> >@@ -2049,15 +2054,25 @@ int smc_conn_create(struct smc_sock *smc, struct smc_init_info *ini) >> > if (rc) >> > goto out; >> > lgr = conn->lgr; >> >- write_lock_bh(&lgr->conns_lock); >> >- rc = smc_lgr_register_conn(conn, true); >> >- write_unlock_bh(&lgr->conns_lock); >> >+ spin_lock_bh(lgr_lock); >> >+ if (lgr->freeing) { >> >+ conn->lgr = NULL; >> >+ rc = SMC_CLC_DECL_SYNCERR; >> >> This should not be SMC_CLC_DECL_SYNCERR, maybe SMC_CLC_DECL_INTERR or add >> a new error code. > >No problem, I will use SMC_CLC_DECL_INTERR in v4. > >> >+ } else { >> >+ write_lock_bh(&lgr->conns_lock); >> >+ rc = smc_lgr_register_conn(conn, true); >> >+ write_unlock_bh(&lgr->conns_lock); >> >+ } >> >+ spin_unlock_bh(lgr_lock); >> > if (rc) { >> > smc_lgr_cleanup_early(lgr); >> >+ smc_lgr_put(lgr); /* lgr_hold in smc_lgr_create() */ >> >> smc_lgr_put() may call smcr_buf_free() -> vfree(), which may sleep. >> And you put it in the spinlock. > >It seems the smc_lgr_put(lgr) is added after the >spin_unlock_bh(lgr_lock). Were you referring to another lock held by a >caller? I will keep this unchanged in v4, let me know if anything >should be adjusted further. No, I mean this part in [PATCH net v3 3/3], sorry for replying to the wrong thread. @@ -89,14 +89,22 @@ static void smc_lgr_schedule_free_work(struct smc_link_group *lgr) * otherwise there is a risk of out-of-sync link groups. */ if (!lgr->freeing) { - mod_delayed_work(system_percpu_wq, &lgr->free_work, - (!lgr->is_smcd && lgr->role == SMC_CLNT) ? - SMC_LGR_FREE_DELAY_CLNT : - SMC_LGR_FREE_DELAY_SERV); + smc_lgr_hold(lgr); /* released by the worker or cancellation */ + if (mod_delayed_work(system_percpu_wq, &lgr->free_work, + (!lgr->is_smcd && lgr->role == SMC_CLNT) ? + SMC_LGR_FREE_DELAY_CLNT : + SMC_LGR_FREE_DELAY_SERV)) + smc_lgr_put(lgr); /* pending work already owns a reference */ } spin_unlock_bh(lgr_lock); Best regards, Dust