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Message-ID: <71aa847b-2edc-44a2-beb7-3610bf744937@linux.alibaba.com>
Date: Mon, 4 Mar 2024 17:00:36 +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][next] net/smc: Avoid -Wflex-array-member-not-at-end
warnings
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:
>
> 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 <gustavoars@...nel.org>
> ---
> 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.
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.
diff --git a/net/smc/smc_clc.c b/net/smc/smc_clc.c
index e55026c7529c..971b4677b84d 100644
--- a/net/smc/smc_clc.c
+++ b/net/smc/smc_clc.c
@@ -855,7 +855,7 @@ int smc_clc_send_proposal(struct smc_sock *smc, struct smc_init_info *ini)
ipv6_prfx = pclc->pclc_prfx_ipv6;
v2_ext = &pclc->pclc_v2_ext;
smcd_v2_ext = &pclc->pclc_smcd_v2_ext;
- gidchids = pclc->pclc_gidchids;
+ gidchids = pclc->pclc_smcd_v2_ext.gidchid;
trl = &pclc->pclc_trl;
pclc_base->hdr.version = SMC_V2;
diff --git a/net/smc/smc_clc.h b/net/smc/smc_clc.h
index 7cc7070b9772..36c8432af73e 100644
--- a/net/smc/smc_clc.h
+++ b/net/smc/smc_clc.h
@@ -133,6 +133,14 @@ struct smc_clc_smcd_gid_chid {
* (https://www.ibm.com/support/pages/node/6326337)
*/
+#define SMC_CLC_MAX_V6_PREFIX 8
+#define SMC_CLC_MAX_UEID 8
+#define SMCD_CLC_MAX_V2_GID_ENTRIES 8 /* max # of CHID-GID entries in CLC
+ * proposal SMC-Dv2 extension.
+ * each ISM device takes one entry and
+ * each Emulated-ISM takes two entries
+ */
+
struct smc_clc_v2_extension {
struct smc_clnt_opts_area_hdr hdr;
u8 roce[16]; /* RoCEv2 GID */
@@ -140,7 +148,7 @@ struct smc_clc_v2_extension {
u8 max_links;
__be16 feature_mask;
u8 reserved[12];
- u8 user_eids[][SMC_MAX_EID_LEN];
+ u8 user_eids[SMC_CLC_MAX_UEID][SMC_MAX_EID_LEN];
};
struct smc_clc_msg_proposal_prefix { /* prefix part of clc proposal message*/
@@ -161,7 +169,7 @@ 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 smc_clc_smcd_gid_chid gidchid[];
+ struct smc_clc_smcd_gid_chid gidchid[SMCD_CLC_MAX_V2_GID_ENTRIES];
};
struct smc_clc_msg_proposal { /* clc proposal message sent by Linux */
@@ -170,24 +178,13 @@ struct smc_clc_msg_proposal { /* clc proposal message sent by Linux */
__be16 iparea_offset; /* offset to IP address information area */
} __aligned(4);
-#define SMC_CLC_MAX_V6_PREFIX 8
-#define SMC_CLC_MAX_UEID 8
-#define SMCD_CLC_MAX_V2_GID_ENTRIES 8 /* max # of CHID-GID entries in CLC
- * proposal SMC-Dv2 extension.
- * each ISM device takes one entry and
- * each Emulated-ISM takes two entries
- */
-
struct smc_clc_msg_proposal_area {
struct smc_clc_msg_proposal pclc_base;
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;
- 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_gid_chid
- pclc_gidchids[SMCD_CLC_MAX_V2_GID_ENTRIES];
struct smc_clc_msg_trail pclc_trl;
};
Thanks!
Wen Gu
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