From 8863b1212aab2c738be9526f90389bc0fc18f90f Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Thu, 7 May 2020 13:55:29 -0500 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 Signed-off-by: Kalle Valo Link: https://lore.kernel.org/r/20200507185529.GA14639@embeddedor --- 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 dd74413..89c6671 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 a3b4905..1e8ab704 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 { -- 2.7.4