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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 7649773293 ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200507185529.GA14639@embeddedor
This commit is contained in:
Gustavo A. R. Silva 2020-05-07 13:55:29 -05:00 committed by Kalle Valo
parent e0e05f20c2
commit 8863b1212a
2 changed files with 13 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
drivers/net/wireless/intel/iwlegacy/commands.h
View File

@ -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;
/******************************************************************************

4
drivers/net/wireless/intel/iwlegacy/iwl-spectrum.h
View File

@ -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 {