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Date: Thu, 7 May 2020 13:55:38 -0500
From: "Gustavo A. R. Silva" <gustavoars@...nel.org>
To: Johannes Berg <johannes.berg@...el.com>,
Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
Luca Coelho <luciano.coelho@...el.com>,
Intel Linux Wireless <linuxwifi@...el.com>
Cc: linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] iwlwifi: Replace zero-length array with flexible-array
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by
this change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
drivers/net/wireless/intel/iwlwifi/dvm/commands.h | 12 ++++++------
drivers/net/wireless/intel/iwlwifi/fw/api/nvm-reg.h | 4 ++--
drivers/net/wireless/intel/iwlwifi/fw/debugfs.c | 2 +-
drivers/net/wireless/intel/iwlwifi/iwl-op-mode.h | 2 +-
drivers/net/wireless/intel/iwlwifi/iwl-trans.h | 2 +-
5 files changed, 11 insertions(+), 11 deletions(-)
diff --git a/drivers/net/wireless/intel/iwlwifi/dvm/commands.h b/drivers/net/wireless/intel/iwlwifi/dvm/commands.h
index 0f4be4be181c..fdcc1292a92b 100644
--- a/drivers/net/wireless/intel/iwlwifi/dvm/commands.h
+++ b/drivers/net/wireless/intel/iwlwifi/dvm/commands.h
@@ -1023,7 +1023,7 @@ struct iwl_wep_cmd {
u8 global_key_type;
u8 flags;
u8 reserved;
- struct iwl_wep_key key[0];
+ struct iwl_wep_key key[];
} __packed;
#define WEP_KEY_WEP_TYPE 1
@@ -1305,7 +1305,7 @@ struct iwl_tx_cmd {
* length is 26 or 30 bytes, followed by payload data
*/
u8 payload[0];
- struct ieee80211_hdr hdr[0];
+ struct ieee80211_hdr hdr[];
} __packed;
/*
@@ -2380,7 +2380,7 @@ struct iwl_scan_cmd {
* for one scan to complete (i.e. receive SCAN_COMPLETE_NOTIFICATION)
* before requesting another scan.
*/
- u8 data[0];
+ u8 data[];
} __packed;
/* Can abort will notify by complete notification with abort status. */
@@ -2475,7 +2475,7 @@ struct iwl_tx_beacon_cmd {
__le16 tim_idx;
u8 tim_size;
u8 reserved1;
- struct ieee80211_hdr frame[0]; /* beacon frame */
+ struct ieee80211_hdr frame[]; /* beacon frame */
} __packed;
/******************************************************************************
@@ -3188,7 +3188,7 @@ struct iwl_calib_hdr {
struct iwl_calib_cmd {
struct iwl_calib_hdr hdr;
- u8 data[0];
+ u8 data[];
} __packed;
struct iwl_calib_xtal_freq_cmd {
@@ -3216,7 +3216,7 @@ struct iwl_calib_temperature_offset_v2_cmd {
/* IWL_PHY_CALIBRATE_CHAIN_NOISE_RESET_CMD */
struct iwl_calib_chain_noise_reset_cmd {
struct iwl_calib_hdr hdr;
- u8 data[0];
+ u8 data[];
};
/* IWL_PHY_CALIBRATE_CHAIN_NOISE_GAIN_CMD */
diff --git a/drivers/net/wireless/intel/iwlwifi/fw/api/nvm-reg.h b/drivers/net/wireless/intel/iwlwifi/fw/api/nvm-reg.h
index 97b49843e318..397ac89a04c2 100644
--- a/drivers/net/wireless/intel/iwlwifi/fw/api/nvm-reg.h
+++ b/drivers/net/wireless/intel/iwlwifi/fw/api/nvm-reg.h
@@ -351,7 +351,7 @@ struct iwl_mcc_update_resp_v3 {
__le16 time;
__le16 geo_info;
__le32 n_channels;
- __le32 channels[0];
+ __le32 channels[];
} __packed; /* LAR_UPDATE_MCC_CMD_RESP_S_VER_3 */
/**
@@ -380,7 +380,7 @@ struct iwl_mcc_update_resp {
u8 source_id;
u8 reserved[3];
__le32 n_channels;
- __le32 channels[0];
+ __le32 channels[];
} __packed; /* LAR_UPDATE_MCC_CMD_RESP_S_VER_4 */
/**
diff --git a/drivers/net/wireless/intel/iwlwifi/fw/debugfs.c b/drivers/net/wireless/intel/iwlwifi/fw/debugfs.c
index 89f74116569d..cc1d93606d9b 100644
--- a/drivers/net/wireless/intel/iwlwifi/fw/debugfs.c
+++ b/drivers/net/wireless/intel/iwlwifi/fw/debugfs.c
@@ -261,7 +261,7 @@ struct hcmd_write_data {
__be32 cmd_id;
__be32 flags;
__be16 length;
- u8 data[0];
+ u8 data[];
} __packed;
static ssize_t iwl_dbgfs_send_hcmd_write(struct iwl_fw_runtime *fwrt, char *buf,
diff --git a/drivers/net/wireless/intel/iwlwifi/iwl-op-mode.h b/drivers/net/wireless/intel/iwlwifi/iwl-op-mode.h
index 3008a5246be8..b35b8920941b 100644
--- a/drivers/net/wireless/intel/iwlwifi/iwl-op-mode.h
+++ b/drivers/net/wireless/intel/iwlwifi/iwl-op-mode.h
@@ -175,7 +175,7 @@ void iwl_opmode_deregister(const char *name);
struct iwl_op_mode {
const struct iwl_op_mode_ops *ops;
- char op_mode_specific[0] __aligned(sizeof(void *));
+ char op_mode_specific[] __aligned(sizeof(void *));
};
static inline void iwl_op_mode_stop(struct iwl_op_mode *op_mode)
diff --git a/drivers/net/wireless/intel/iwlwifi/iwl-trans.h b/drivers/net/wireless/intel/iwlwifi/iwl-trans.h
index bba527b339b5..3fbbbac0953d 100644
--- a/drivers/net/wireless/intel/iwlwifi/iwl-trans.h
+++ b/drivers/net/wireless/intel/iwlwifi/iwl-trans.h
@@ -878,7 +878,7 @@ struct iwl_trans {
/* pointer to trans specific struct */
/*Ensure that this pointer will always be aligned to sizeof pointer */
- char trans_specific[0] __aligned(sizeof(void *));
+ char trans_specific[] __aligned(sizeof(void *));
};
const char *iwl_get_cmd_string(struct iwl_trans *trans, u32 id);
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