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Message-ID: <f504328f-1fd2-4c85-a657-a14b272c321e@linux.alibaba.com>
Date: Mon, 25 Mar 2024 11:01:04 +0800
From: Wen Gu <guwen@...ux.alibaba.com>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>,
Wenjia Zhang <wenjia@...ux.ibm.com>, Jan Karcher <jaka@...ux.ibm.com>,
"D. Wythe" <alibuda@...ux.alibaba.com>, Tony Lu <tonylu@...ux.alibaba.com>,
"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: linux-s390@...r.kernel.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v2][next] net/smc: Avoid -Wflex-array-member-not-at-end
warnings
On 2024/3/13 01:55, 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:
>
> 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_fixed, fixed,
> 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_fixed pclc_v2_ext;
> ...
> struct smc_clc_smcd_v2_extension_fixed 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;
> | ^~~~~~~~~~~~~~~~
>
> Reviewed-by: Kees Cook <keescook@...omium.org>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
Hi Gustavo,
Thank you for the v2. Some places may need improvement, see below.
> ---
> Changes in v2:
> - Name the tagged struct *_fixed instead of *_hdr.
> - Add Kees' RB tag.
>
> 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..63bb5745ab54 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, fixed);
checkpatch complained 'WARNING: line length of 86 exceeds 80 columns' here.
It can be reproduced by:
./scripts/checkpatch.pl --strict --max-line-length=80
--ignore=COMMIT_LOG_LONG_LINE,MACRO_ARG_REUSE,ALLOC_SIZEOF_STRUCT,NO_AUTHOR_SIGN_OFF,GIT_COMMIT_ID,CAMELCASE xxx.patch
> + smcd_v2_ext = container_of(&pclc->pclc_smcd_v2_ext,
> + struct smc_clc_smcd_v2_extension, fixed);
> gidchids = pclc->pclc_gidchids;
> trl = &pclc->pclc_trl;
>
> diff --git a/net/smc/smc_clc.h b/net/smc/smc_clc.h
> index 7cc7070b9772..2bfb51daf468 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_fixed, fixed,
> + struct smc_clnt_opts_area_hdr hdr;
checkpatch: 'CHECK: Alignment should match open parenthesis'
> + 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_fixed, fixed,
> + u8 system_eid[SMC_MAX_EID_LEN];
checkpatch: 'CHECK: Alignment should match open parenthesis'
Thanks!
Wen Gu
> + 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_fixed 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_fixed 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;
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