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Message-ID: <20200507185529.GA14639@embeddedor>
Date: Thu, 7 May 2020 13:55:29 -0500
From: "Gustavo A. R. Silva" <gustavoars@...nel.org>
To: Stanislaw Gruszka <stf_xl@...pl>
Cc: linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] iwlegacy: 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/iwlegacy/commands.h | 22 ++++++++++-----------
drivers/net/wireless/intel/iwlegacy/iwl-spectrum.h | 4 +--
2 files changed, 13 insertions(+), 13 deletions(-)
diff --git a/drivers/net/wireless/intel/iwlegacy/commands.h b/drivers/net/wireless/intel/iwlegacy/commands.h
index dd744135c956..89c6671b32bc 100644
--- a/drivers/net/wireless/intel/iwlegacy/commands.h
+++ b/drivers/net/wireless/intel/iwlegacy/commands.h
@@ -203,7 +203,7 @@ struct il_cmd_header {
__le16 sequence;
/* command or response/notification data follows immediately */
- u8 data[0];
+ u8 data[];
} __packed;
/**
@@ -1112,7 +1112,7 @@ struct il_wep_cmd {
u8 global_key_type;
u8 flags;
u8 reserved;
- struct il_wep_key key[0];
+ struct il_wep_key key[];
} __packed;
#define WEP_KEY_WEP_TYPE 1
@@ -1166,7 +1166,7 @@ struct il3945_rx_frame_stats {
u8 agc;
__le16 sig_avg;
__le16 noise_diff;
- u8 payload[0];
+ u8 payload[];
} __packed;
struct il3945_rx_frame_hdr {
@@ -1175,7 +1175,7 @@ struct il3945_rx_frame_hdr {
u8 reserved1;
u8 rate;
__le16 len;
- u8 payload[0];
+ u8 payload[];
} __packed;
struct il3945_rx_frame_end {
@@ -1211,7 +1211,7 @@ struct il4965_rx_non_cfg_phy {
__le16 ant_selection; /* ant A bit 4, ant B bit 5, ant C bit 6 */
__le16 agc_info; /* agc code 0:6, agc dB 7:13, reserved 14:15 */
u8 rssi_info[6]; /* we use even entries, 0/2/4 for A/B/C rssi */
- u8 pad[0];
+ u8 pad[];
} __packed;
/*
@@ -1409,7 +1409,7 @@ struct il3945_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;
/*
@@ -1511,7 +1511,7 @@ struct il_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;
/* TX command response is sent after *3945* transmission attempts.
@@ -2520,7 +2520,7 @@ struct il3945_scan_cmd {
* for one scan to complete (i.e. receive N_SCAN_COMPLETE)
* before requesting another scan.
*/
- u8 data[0];
+ u8 data[];
} __packed;
struct il_scan_cmd {
@@ -2564,7 +2564,7 @@ struct il_scan_cmd {
* for one scan to complete (i.e. receive N_SCAN_COMPLETE)
* before requesting another scan.
*/
- u8 data[0];
+ u8 data[];
} __packed;
/* Can abort will notify by complete notification with abort status. */
@@ -2664,7 +2664,7 @@ struct il3945_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;
struct il_tx_beacon_cmd {
@@ -2672,7 +2672,7 @@ struct il_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;
/******************************************************************************
diff --git a/drivers/net/wireless/intel/iwlegacy/iwl-spectrum.h b/drivers/net/wireless/intel/iwlegacy/iwl-spectrum.h
index a3b490501a70..1e8ab704dbfb 100644
--- a/drivers/net/wireless/intel/iwlegacy/iwl-spectrum.h
+++ b/drivers/net/wireless/intel/iwlegacy/iwl-spectrum.h
@@ -53,7 +53,7 @@ struct ieee80211_measurement_params {
struct ieee80211_info_element {
u8 id;
u8 len;
- u8 data[0];
+ u8 data[];
} __packed;
struct ieee80211_measurement_request {
@@ -61,7 +61,7 @@ struct ieee80211_measurement_request {
u8 token;
u8 mode;
u8 type;
- struct ieee80211_measurement_params params[0];
+ struct ieee80211_measurement_params params[];
} __packed;
struct ieee80211_measurement_report {
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