Commit 45c21a0e authored by Gustavo A. R. Silva's avatar Gustavo A. R. Silva Committed by Luca Coelho
Browse files

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 76497732 ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: default avatarGustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20200507185538.GA14674@embeddedor


Signed-off-by: default avatarLuca Coelho <luciano.coelho@intel.com>
parent f1269463

drivers/net/wireless/intel/iwlwifi/dvm/commands.h

+6 −6
Original line number Diff line number Diff line
@@ -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 */

drivers/net/wireless/intel/iwlwifi/fw/api/nvm-reg.h

+2 −2
Original line number Diff line number Diff line
@@ -361,7 +361,7 @@ 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 */



/**
@@ -390,7 +390,7 @@ 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 */



/**

drivers/net/wireless/intel/iwlwifi/fw/debugfs.c

+1 −1
Original line number Diff line number Diff line
@@ -260,7 +260,7 @@ 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,

drivers/net/wireless/intel/iwlwifi/iwl-op-mode.h

+1 −1
Original line number Diff line number Diff line
@@ -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)

drivers/net/wireless/intel/iwlwifi/iwl-trans.h

+1 −1
Original line number Diff line number Diff line
@@ -1006,7 +1006,7 @@ 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);