On Thu, Apr 03, 2025 at 08:42:00PM -0600, Gustavo A. R. Silva wrote: > -Wflex-array-member-not-at-end was introduced in GCC-14, and we are > getting ready to enable it, globally. > > So, in order to avoid ending up with a flexible-array member in the > middle of multiple other structs, we use the `__struct_group()` > helper to create a new tagged `struct iwl_tx_cmd_hdr`. This structure > groups together all the members of the flexible `struct iwl_tx_cmd` > except the flexible array. > > As a result, the array is effectively separated from the rest of the > members without modifying the memory layout of the flexible structure. > We then change the type of the middle struct members currently causing > trouble from `struct iwl_tx_cmd` to `struct iwl_tx_cmd_hdr`. > > We also want to ensure that when new members need to be added to the > flexible structure, they are always included within the newly created > tagged struct. For this, we use `static_assert()`. This ensures that the > memory layout for both the flexible structure and the new tagged struct > is the same after any changes. > > This approach avoids having to implement `struct iwl_tx_cmd_hdr` > as a completely separate structure, thus preventing having to maintain > two independent but basically identical structures, closing the door > to potential bugs in the future. > > We also use `container_of()` whenever we need to retrieve a pointer to > the flexible structure, through which we can access the flexible-array > member, if necessary. > > So, with these changes, fix the following warnings: > > drivers/net/wireless/intel/iwlwifi/mld/../fw/api/tdls.h:134:27: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > drivers/net/wireless/intel/iwlwifi/mld/../fw/api/tdls.h:53:27: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > drivers/net/wireless/intel/iwlwifi/mld/../fw/api/tx.h:745:27: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > drivers/net/wireless/intel/iwlwifi/mld/../fw/api/tx.h:764:27: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > drivers/net/wireless/intel/iwlwifi/mvm/../fw/api/tdls.h:134:27: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > drivers/net/wireless/intel/iwlwifi/mvm/../fw/api/tdls.h:53:27: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > drivers/net/wireless/intel/iwlwifi/mvm/../fw/api/tx.h:745:27: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > drivers/net/wireless/intel/iwlwifi/mvm/../fw/api/tx.h:764:27: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] > > Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx> > --- > This patch is quite similar to the following one: > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e74c0a7875cfec27c25f582f001cc4625a0f8c07 > > Thanks! > > .../net/wireless/intel/iwlwifi/fw/api/tdls.h | 4 +- > .../net/wireless/intel/iwlwifi/fw/api/tx.h | 60 ++++++++++--------- > .../net/wireless/intel/iwlwifi/mvm/mac-ctxt.c | 8 ++- > drivers/net/wireless/intel/iwlwifi/mvm/tdls.c | 10 ++-- > 4 files changed, 44 insertions(+), 38 deletions(-) > > diff --git a/drivers/net/wireless/intel/iwlwifi/fw/api/tdls.h b/drivers/net/wireless/intel/iwlwifi/fw/api/tdls.h > index cfa6532a3cdd..02198bc37f8c 100644 > --- a/drivers/net/wireless/intel/iwlwifi/fw/api/tdls.h > +++ b/drivers/net/wireless/intel/iwlwifi/fw/api/tdls.h > @@ -50,7 +50,7 @@ struct iwl_tdls_channel_switch_timing { > */ > struct iwl_tdls_channel_switch_frame { > __le32 switch_time_offset; > - struct iwl_tx_cmd tx_cmd; > + struct iwl_tx_cmd_hdr tx_cmd; > u8 data[IWL_TDLS_CH_SW_FRAME_MAX_SIZE]; > } __packed; /* TDLS_STA_CHANNEL_SWITCH_FRAME_API_S_VER_1 */ > > @@ -131,7 +131,7 @@ struct iwl_tdls_config_cmd { > struct iwl_tdls_sta_info sta_info[IWL_TDLS_STA_COUNT]; > > __le32 pti_req_data_offset; > - struct iwl_tx_cmd pti_req_tx_cmd; > + struct iwl_tx_cmd_hdr pti_req_tx_cmd; > u8 pti_req_template[]; > } __packed; /* TDLS_CONFIG_CMD_API_S_VER_1 */ > > diff --git a/drivers/net/wireless/intel/iwlwifi/fw/api/tx.h b/drivers/net/wireless/intel/iwlwifi/fw/api/tx.h > index 0a39e4b6eb62..5c0c7bac36d6 100644 > --- a/drivers/net/wireless/intel/iwlwifi/fw/api/tx.h > +++ b/drivers/net/wireless/intel/iwlwifi/fw/api/tx.h > @@ -222,34 +222,36 @@ enum iwl_tx_offload_assist_flags_pos { > * and then the actial payload. > */ > struct iwl_tx_cmd { > - __le16 len; > - __le16 offload_assist; > - __le32 tx_flags; > - struct { > - u8 try_cnt; > - u8 btkill_cnt; > - __le16 reserved; > - } scratch; /* DRAM_SCRATCH_API_U_VER_1 */ > - __le32 rate_n_flags; > - u8 sta_id; > - u8 sec_ctl; > - u8 initial_rate_index; > - u8 reserved2; > - u8 key[16]; > - __le32 reserved3; > - __le32 life_time; > - __le32 dram_lsb_ptr; > - u8 dram_msb_ptr; > - u8 rts_retry_limit; > - u8 data_retry_limit; > - u8 tid_tspec; > - __le16 pm_frame_timeout; > - __le16 reserved4; > - union { > - DECLARE_FLEX_ARRAY(u8, payload); > - DECLARE_FLEX_ARRAY(struct ieee80211_hdr, hdr); > - }; I see no mention in the commit log of the removal of this union (I assume "payload" is never used?) > + /* New members MUST be added within the __struct_group() macro below. */ > + __struct_group(iwl_tx_cmd_hdr, __hdr, __packed, > + __le16 len; > + __le16 offload_assist; > + __le32 tx_flags; > + struct { > + u8 try_cnt; > + u8 btkill_cnt; > + __le16 reserved; > + } scratch; /* DRAM_SCRATCH_API_U_VER_1 */ > + __le32 rate_n_flags; > + u8 sta_id; > + u8 sec_ctl; > + u8 initial_rate_index; > + u8 reserved2; > + u8 key[16]; > + __le32 reserved3; > + __le32 life_time; > + __le32 dram_lsb_ptr; > + u8 dram_msb_ptr; > + u8 rts_retry_limit; > + u8 data_retry_limit; > + u8 tid_tspec; > + __le16 pm_frame_timeout; > + __le16 reserved4; > + ); > + struct ieee80211_hdr hdr[]; > } __packed; /* TX_CMD_API_S_VER_6 */ > +static_assert(offsetof(struct iwl_tx_cmd, hdr) == sizeof(struct iwl_tx_cmd_hdr), > + "struct member likely outside of __struct_group()"); > > struct iwl_dram_sec_info { > __le32 pn_low; > @@ -742,7 +744,7 @@ struct iwl_compressed_ba_notif { > * @frame: the template of the beacon frame > */ > struct iwl_mac_beacon_cmd_v6 { > - struct iwl_tx_cmd tx; > + struct iwl_tx_cmd_hdr tx; > __le32 template_id; > __le32 tim_idx; > __le32 tim_size; > @@ -761,7 +763,7 @@ struct iwl_mac_beacon_cmd_v6 { > * @frame: the template of the beacon frame > */ > struct iwl_mac_beacon_cmd_v7 { > - struct iwl_tx_cmd tx; > + struct iwl_tx_cmd_hdr tx; > __le32 template_id; > __le32 tim_idx; > __le32 tim_size; > diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/mac-ctxt.c b/drivers/net/wireless/intel/iwlwifi/mvm/mac-ctxt.c > index bec18d197f31..f010e68b4a55 100644 > --- a/drivers/net/wireless/intel/iwlwifi/mvm/mac-ctxt.c > +++ b/drivers/net/wireless/intel/iwlwifi/mvm/mac-ctxt.c > @@ -1032,7 +1032,9 @@ static int iwl_mvm_mac_ctxt_send_beacon_v6(struct iwl_mvm *mvm, > struct iwl_mvm_vif *mvmvif = iwl_mvm_vif_from_mac80211(vif); > struct iwl_mac_beacon_cmd_v6 beacon_cmd = {}; > > - iwl_mvm_mac_ctxt_set_tx(mvm, vif, beacon, &beacon_cmd.tx); > + iwl_mvm_mac_ctxt_set_tx(mvm, vif, beacon, > + container_of(&beacon_cmd.tx, > + struct iwl_tx_cmd, __hdr)); > > beacon_cmd.template_id = cpu_to_le32((u32)mvmvif->id); > > @@ -1052,7 +1054,9 @@ static int iwl_mvm_mac_ctxt_send_beacon_v7(struct iwl_mvm *mvm, > struct iwl_mvm_vif *mvmvif = iwl_mvm_vif_from_mac80211(vif); > struct iwl_mac_beacon_cmd_v7 beacon_cmd = {}; > > - iwl_mvm_mac_ctxt_set_tx(mvm, vif, beacon, &beacon_cmd.tx); > + iwl_mvm_mac_ctxt_set_tx(mvm, vif, beacon, > + container_of(&beacon_cmd.tx, > + struct iwl_tx_cmd, __hdr)); > > beacon_cmd.template_id = cpu_to_le32((u32)mvmvif->id); > > diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/tdls.c b/drivers/net/wireless/intel/iwlwifi/mvm/tdls.c > index 36379b738de1..bcfae05192ad 100644 > --- a/drivers/net/wireless/intel/iwlwifi/mvm/tdls.c > +++ b/drivers/net/wireless/intel/iwlwifi/mvm/tdls.c > @@ -342,6 +342,8 @@ iwl_mvm_tdls_config_channel_switch(struct iwl_mvm *mvm, > struct iwl_tdls_channel_switch_cmd_tail *tail = > iwl_mvm_chan_info_cmd_tail(mvm, &cmd.ci); > u16 len = sizeof(cmd) - iwl_mvm_chan_info_padding(mvm); > + struct iwl_tx_cmd *tx_cmd = > + container_of(&tail->frame.tx_cmd, struct iwl_tx_cmd, __hdr); > int ret; > > lockdep_assert_held(&mvm->mutex); > @@ -410,14 +412,12 @@ iwl_mvm_tdls_config_channel_switch(struct iwl_mvm *mvm, > ret = -EINVAL; > goto out; > } > - iwl_mvm_set_tx_cmd_ccmp(info, &tail->frame.tx_cmd); > + iwl_mvm_set_tx_cmd_ccmp(info, tx_cmd); > } > > - iwl_mvm_set_tx_cmd(mvm, skb, &tail->frame.tx_cmd, info, > - mvmsta->deflink.sta_id); > + iwl_mvm_set_tx_cmd(mvm, skb, tx_cmd, info, mvmsta->deflink.sta_id); > > - iwl_mvm_set_tx_cmd_rate(mvm, &tail->frame.tx_cmd, info, sta, > - hdr->frame_control); > + iwl_mvm_set_tx_cmd_rate(mvm, tx_cmd, info, sta, hdr->frame_control); > rcu_read_unlock(); > > memcpy(tail->frame.data, skb->data, skb->len); Otherwise looks good to me. Reviewed-by: Kees Cook <kees@xxxxxxxxxx> -- Kees Cook
