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Thu, 14 May 2026 03:19:48 -0700 (PDT) Received: from [192.168.88.32] ([216.128.9.106]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48fd6276741sm26923115e9.0.2026.05.14.03.19.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 14 May 2026 03:19:48 -0700 (PDT) Message-ID: Date: Thu, 14 May 2026 12:19:46 +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] net/smc: reject CHID-0 ACCEPT that matches an empty ism_dev slot To: Xiang Mei , netdev@vger.kernel.org Cc: alibuda@linux.alibaba.com, dust.li@linux.alibaba.com, sidraya@linux.ibm.com, wenjia@linux.ibm.com, ubraun@linux.ibm.com, linux-rdma@vger.kernel.org, linux-s390@vger.kernel.org, bestswngs@gmail.com References: <20260511062138.2839584-1-xmei5@asu.edu> From: Paolo Abeni Content-Language: en-US In-Reply-To: <20260511062138.2839584-1-xmei5@asu.edu> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/11/26 8:21 AM, Xiang Mei wrote: > On the SMC-D client, slot 0 of ini->ism_dev[]/ini->ism_chid[] is > reserved for an SMC-Dv1 device. smc_find_ism_v2_device_clnt() > populates V2 entries starting at index 1, so when no V1 device is > selected slot 0 is left in its kzalloc()'ed state with ism_dev[0] == > NULL and ism_chid[0] == 0. > > smc_v2_determine_accepted_chid() then matches the peer's CHID against > the array starting from index 0 using the CHID alone. A malicious > peer replying to a SMC-Dv2-only proposal with d1.chid == 0 matches > the empty slot, ini->ism_selected becomes 0, and the subsequent > ism_dev[0]->lgr_lock dereference in smc_conn_create() faults at > offsetof(struct smcd_dev, lgr_lock) == 0x68: > > BUG: KASAN: null-ptr-deref in _raw_spin_lock_bh+0x79/0xe0 > Write of size 4 at addr 0000000000000068 by task exploit/144 > Call Trace: > _raw_spin_lock_bh > smc_conn_create (net/smc/smc_core.c:1997) > __smc_connect (net/smc/af_smc.c:1447) > smc_connect (net/smc/af_smc.c:1720) > __sys_connect > __x64_sys_connect > do_syscall_64 > > Require ism_dev[i] to be non-NULL before accepting a CHID match. > > Fixes: a7c9c5f4af7f ("net/smc: CLC accept / confirm V2") > Reported-by: Weiming Shi > Assisted-by: Claude:claude-opus-4-7 > Signed-off-by: Xiang Mei > --- > net/smc/af_smc.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c > index 185dbed7de5d..12ea3b6dbc64 100644 > --- a/net/smc/af_smc.c > +++ b/net/smc/af_smc.c > @@ -1400,7 +1400,8 @@ smc_v2_determine_accepted_chid(struct smc_clc_msg_accept_confirm *aclc, > int i; > > for (i = 0; i < ini->ism_offered_cnt + 1; i++) { > - if (ini->ism_chid[i] == ntohs(aclc->d1.chid)) { > + if (ini->ism_dev[i] && > + ini->ism_chid[i] == ntohs(aclc->d1.chid)) { > ini->ism_selected = i; > return 0; > } Patch LGTM, thanks! @smc maintainers, please note that sashiko reviews: https://sashiko.dev/#/patchset/20260511062138.2839584-1-xmei5%40asu.edu pointed to another pre-existing issue in this area you may want to address. /P