From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-99.freemail.mail.aliyun.com (out30-99.freemail.mail.aliyun.com [115.124.30.99]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8DDC61B599; Mon, 11 Mar 2024 10:59:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.99 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710154760; cv=none; b=A+HOnEvhxL/liMycZFMpdSeAvSwVgG9bvsRwg2dGFktOdRBJuq64412GD2IPPx91gEtEfI3Opo5RncRqvtUJ0phDEjJ2dlehORuSKq9i4Q8VZUJL73hdkhvYoedWgpFiCkcLGFi91BMsQ/cHcSPQMFMZY9hT82C6qMYEm2l485k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710154760; c=relaxed/simple; bh=oXZqPOZ6YIXTm+WG3dgEh3MLHaLjbWnhRyHghOoWAP0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=RrzIhkU0DyA6/bxcjE/055hVZQouSDQNYK0sZzXliOAa8Haq3AbJfJnkT3lTQW5zssiQFj38v0Y8QZV6PMwxGz0Ji4LDX24paWfmx1fIyc9msqyPIlZT+ukQd92uyTGraCDdf2FdQGfKccelRU3gs9GcERXwJAgf+H0uBZkLcqs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=dZlizvyf; arc=none smtp.client-ip=115.124.30.99 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) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="dZlizvyf" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1710154754; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=IcfjheDQ5kV24cq9Mvp8h+viyjO4uKlMJPaqsPHtqgU=; b=dZlizvyfLA2e1s/alWGuZ0mTpSw7DUtdEV/KI3y1q0K0tVdZeRMz4E4YeN3cdxtSVGcY46dg4c8MOaIbe0Pm4086Q1npZK1ykfq8SeElZjf+93i7Jes+9JWmZWmEJ5LSSXJuN4SgfV6bmzWUmzcaYzWoobamLobiokJSnWqm6bQ= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R171e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046059;MF=guwen@linux.alibaba.com;NM=1;PH=DS;RN=15;SR=0;TI=SMTPD_---0W2FTvzX_1710154752; Received: from 30.221.129.118(mailfrom:guwen@linux.alibaba.com fp:SMTPD_---0W2FTvzX_1710154752) by smtp.aliyun-inc.com; Mon, 11 Mar 2024 18:59:13 +0800 Message-ID: Date: Mon, 11 Mar 2024 18:59:12 +0800 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH][next] net/smc: Avoid -Wflex-array-member-not-at-end warnings To: "Gustavo A. R. Silva" , Jan Karcher , "Gustavo A. R. Silva" , Wenjia Zhang , "D. Wythe" , Tony Lu , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: linux-s390@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, Kees Cook References: <71aa847b-2edc-44a2-beb7-3610bf744937@linux.alibaba.com> <1cb9a110-c877-4420-9b23-1e7980f1300a@linux.ibm.com> <82c1dc9e-d5b6-40e3-9d81-d18cc270724b@embeddedor.com> From: Wen Gu In-Reply-To: <82c1dc9e-d5b6-40e3-9d81-d18cc270724b@embeddedor.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2024/3/8 07:46, Gustavo A. R. Silva wrote: > > > On 3/7/24 02:17, Jan Karcher wrote: >> >> >> On 04/03/2024 10:00, Wen Gu wrote: >>> >>> >>> On 2024/3/2 02:40, Gustavo A. R. Silva wrote: >>>> -Wflex-array-member-not-at-end is coming in GCC-14, and we are getting >>>> ready to enable it globally. >>>> >>>> There are currently a couple of objects in `struct smc_clc_msg_proposal_area` >>>> that contain a couple of flexible structures: >>>> >> >> Thank you Gustavo for the proposal. >> I had to do some reading to better understand what's happening and how your patch solves this. >> >>>> struct smc_clc_msg_proposal_area { >>>>     ... >>>>     struct smc_clc_v2_extension             pclc_v2_ext; >>>>     ... >>>>     struct smc_clc_smcd_v2_extension        pclc_smcd_v2_ext; >>>>     ... >>>> }; >>>> >>>> So, in order to avoid ending up with a couple of flexible-array members >>>> in the middle of a struct, we use the `struct_group_tagged()` helper to >>>> separate the flexible array from the rest of the members in the flexible >>>> structure: >>>> >>>> struct smc_clc_smcd_v2_extension { >>>>          struct_group_tagged(smc_clc_smcd_v2_extension_hdr, hdr, >>>>                              u8 system_eid[SMC_MAX_EID_LEN]; >>>>                              u8 reserved[16]; >>>>          ); >>>>          struct smc_clc_smcd_gid_chid gidchid[]; >>>> }; >>>> >>>> With the change described above, we now declare objects of the type of >>>> the tagged struct without embedding flexible arrays in the middle of >>>> another struct: >>>> >>>> struct smc_clc_msg_proposal_area { >>>>          ... >>>>          struct smc_clc_v2_extension_hdr        pclc_v2_ext; >>>>          ... >>>>          struct smc_clc_smcd_v2_extension_hdr    pclc_smcd_v2_ext; >>>>          ... >>>> }; >>>> >>>> We also use `container_of()` when we need to retrieve a pointer to the >>>> flexible structures. >>>> >>>> So, with these changes, fix the following warnings: >>>> >>>> In file included from net/smc/af_smc.c:42: >>>> net/smc/smc_clc.h:186:49: warning: structure containing a flexible array member is not at the end of another >>>> structure [-Wflex-array-member-not-at-end] >>>>    186 |         struct smc_clc_v2_extension             pclc_v2_ext; >>>>        |                                                 ^~~~~~~~~~~ >>>> net/smc/smc_clc.h:188:49: warning: structure containing a flexible array member is not at the end of another >>>> structure [-Wflex-array-member-not-at-end] >>>>    188 |         struct smc_clc_smcd_v2_extension pclc_smcd_v2_ext; >>>>        |                                                 ^~~~~~~~~~~~~~~~ >>>> >>>> Signed-off-by: Gustavo A. R. Silva >>>> --- >>>>   net/smc/smc_clc.c |  5 +++-- >>>>   net/smc/smc_clc.h | 24 ++++++++++++++---------- >>>>   2 files changed, 17 insertions(+), 12 deletions(-) >>>> >>>> diff --git a/net/smc/smc_clc.c b/net/smc/smc_clc.c >>>> index e55026c7529c..3094cfa1c458 100644 >>>> --- a/net/smc/smc_clc.c >>>> +++ b/net/smc/smc_clc.c >>>> @@ -853,8 +853,9 @@ int smc_clc_send_proposal(struct smc_sock *smc, struct smc_init_info *ini) >>>>       pclc_smcd = &pclc->pclc_smcd; >>>>       pclc_prfx = &pclc->pclc_prfx; >>>>       ipv6_prfx = pclc->pclc_prfx_ipv6; >>>> -    v2_ext = &pclc->pclc_v2_ext; >>>> -    smcd_v2_ext = &pclc->pclc_smcd_v2_ext; >>>> +    v2_ext = container_of(&pclc->pclc_v2_ext, struct smc_clc_v2_extension, _hdr); >>>> +    smcd_v2_ext = container_of(&pclc->pclc_smcd_v2_ext, >>>> +                   struct smc_clc_smcd_v2_extension, hdr); >>>>       gidchids = pclc->pclc_gidchids; >>>>       trl = &pclc->pclc_trl; >>>> diff --git a/net/smc/smc_clc.h b/net/smc/smc_clc.h >>>> index 7cc7070b9772..5b91a1947078 100644 >>>> --- a/net/smc/smc_clc.h >>>> +++ b/net/smc/smc_clc.h >>>> @@ -134,12 +134,14 @@ struct smc_clc_smcd_gid_chid { >>>>                */ >>>>   struct smc_clc_v2_extension { >>>> -    struct smc_clnt_opts_area_hdr hdr; >>>> -    u8 roce[16];        /* RoCEv2 GID */ >>>> -    u8 max_conns; >>>> -    u8 max_links; >>>> -    __be16 feature_mask; >>>> -    u8 reserved[12]; >>>> +    struct_group_tagged(smc_clc_v2_extension_hdr, _hdr, >>>> +        struct smc_clnt_opts_area_hdr hdr; >>>> +        u8 roce[16];        /* RoCEv2 GID */ >>>> +        u8 max_conns; >>>> +        u8 max_links; >>>> +        __be16 feature_mask; >>>> +        u8 reserved[12]; >>>> +    ); >>>>       u8 user_eids[][SMC_MAX_EID_LEN]; >>>>   }; >>>> @@ -159,8 +161,10 @@ struct smc_clc_msg_smcd {    /* SMC-D GID information */ >>>>   }; >>>>   struct smc_clc_smcd_v2_extension { >>>> -    u8 system_eid[SMC_MAX_EID_LEN]; >>>> -    u8 reserved[16]; >>>> +    struct_group_tagged(smc_clc_smcd_v2_extension_hdr, hdr, >>>> +        u8 system_eid[SMC_MAX_EID_LEN]; >>>> +        u8 reserved[16]; >>>> +    ); >>>>       struct smc_clc_smcd_gid_chid gidchid[]; >>>>   }; >>>> @@ -183,9 +187,9 @@ struct smc_clc_msg_proposal_area { >>>>       struct smc_clc_msg_smcd            pclc_smcd; >>>>       struct smc_clc_msg_proposal_prefix    pclc_prfx; >>>>       struct smc_clc_ipv6_prefix pclc_prfx_ipv6[SMC_CLC_MAX_V6_PREFIX]; >>>> -    struct smc_clc_v2_extension        pclc_v2_ext; >>>> +    struct smc_clc_v2_extension_hdr        pclc_v2_ext; >>>>       u8            user_eids[SMC_CLC_MAX_UEID][SMC_MAX_EID_LEN]; >>>> -    struct smc_clc_smcd_v2_extension    pclc_smcd_v2_ext; >>>> +    struct smc_clc_smcd_v2_extension_hdr    pclc_smcd_v2_ext; >>>>       struct smc_clc_smcd_gid_chid >>>>                   pclc_gidchids[SMCD_CLC_MAX_V2_GID_ENTRIES]; >>>>       struct smc_clc_msg_trail        pclc_trl; >>> >>> Thank you! Gustavo. This patch can fix this warning well, just the name >>> '*_hdr' might not be very accurate, but I don't have a good idea ATM. >> >> I agree. Should we chose this option we should come up for a better name. >> >>> >>> Besides, I am wondering if this can be fixed by moving >>> user_eids of smc_clc_msg_proposal_area into smc_clc_v2_extension, >>> and >>> pclc_gidchids of smc_clc_msg_proposal_area into smc_clc_smcd_v2_extension. >>> >>> so that we can avoid to use the flexible-array in smc_clc_v2_extension >>> and smc_clc_smcd_v2_extension. >> >> I like the idea and put some thought into it. The only thing that is not perfectly clean IMO is the following: >> By the current definition it is easily visible that we are dealing with a variable sized array. If we move them into >> the structs one could think they are always at their MAX size which they are not. >> E.g.: An incoming proposal can have 0 UEIDs indicated by the eid_cnt. >> That said nothing a comment can't fix. >> >>  From what i have seen the offset and length calculations regarding the "real" size of those structs is fine with your >> proposal. >> >> Can you verify that your changes also resolve the warnings? > > I can confirm that the changes Wen Gu is proposing also resolve the warnings. > > Wen, > > If you send a proper patch, you can include the following tags: > > Reviewed-by: Gustavo A. R. Silva > Build-tested-by: Gustavo A. R. Silva > Hi Gustavo, thank you for the confirmation that my proposal can fix the warning. But I found that I may have something missed in my proposal when I think further. My proposal changed the sizes of struct smc_clc_v2_extension and smc_clc_smcd_v2_extension, and some places in SMC need them, such as the fill of kvec in smc_clc_send_proposal(). So my proposal may involve more changes to current SMC code, and I think it is not as clean as your solution. So I perfer yours now. And as for the name, I think maybe we can use '*_elems' as a suffix, at least it is unambiguous. So it will be smc_clc_v2_extension_elems and smc_clc_smcd_v2_extension_elems. Jan, what do you think of the name '*_elems' ? Thanks! > Thanks! > -- > Gustavo > >> >> [...] >> >>>   }; >>> >>> >>> Thanks! >>> Wen Gu >> >> Thanks you >> - Jan