wifi: brcmfmac: common: Replace one-element array with flexible-array member

Hi!

This series aims to replace a one-element array with flexible-array member in drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwil_types.h (in struct brcmf_dload_data_le) and use the struct_size() helper.

This helps with the ongoing efforts to tighten the FORTIFY_SOURCE routines on memcpy() and help us make progress towards globally enabling -fstrict-flex-arrays=3 [1].

Gustavo A. R. Silva (2):
wifi: brcmfmac: replace one-element array with flexible-array member
in struct brcmf_dload_data_le
wifi: brcmfmac: Use struct_size() in code ralated to struct
brcmf_dload_data_le

 drivers/net/wireless/broadcom/brcm80211/brcmfmac/common.c  | 7 ++++---
 .../net/wireless/broadcom/brcm80211/brcmfmac/fwil_types.h  | 2 +-
 2 files changed, 5 insertions(+), 4 deletions(-)

2.34.1

One-element arrays are deprecated, and we are replacing them with flexible array members instead. So, replace one-element array with flexible-array member in struct brcmf_dload_data_le.

Important to mention is that doing a build before/after this patch results in no binary output differences.

This helps with the ongoing efforts to tighten the FORTIFY_SOURCE routines on memcpy() and help us make progress towards globally enabling -fstrict-flex-arrays=3 [1].

---
 drivers/net/wireless/broadcom/brcm80211/brcmfmac/common.c     | 4 ++--
 drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwil_types.h | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

index 22344e68fd59..2e836566e218 100644
@@ -110,7 +110,7 @@ static int brcmf_c_download(struct brcmf_if *ifp, u16 flag,
 	dload_buf->dload_type = cpu_to_le16(DL_TYPE_CLM);
 	dload_buf->len = cpu_to_le32(len);
 	dload_buf->crc = cpu_to_le32(0);
-	len = sizeof(*dload_buf) + len - 1;
+	len = sizeof(*dload_buf) + len;
 
 	err = brcmf_fil_iovar_data_set(ifp, "clmload", dload_buf, len);
 

@@ -139,7 +139,7 @@ static int brcmf_c_process_clm_blob(struct brcmf_if *ifp)
 		return 0;
 	}
 
-	chunk_buf = kzalloc(sizeof(*chunk_buf) + MAX_CHUNK_LEN - 1, GFP_KERNEL);
+	chunk_buf = kzalloc(sizeof(*chunk_buf) + MAX_CHUNK_LEN, GFP_KERNEL);
 	if (!chunk_buf) {
 		err = -ENOMEM;
 		goto done;

index f518e025d6e4..a69339f72c66 100644
@@ -943,7 +943,7 @@ struct brcmf_dload_data_le {
 	__le16 dload_type;
 	__le32 len;
 	__le32 crc;
-	u8 data[1];
+	u8 data[];
 };
 
 /**

2.34.1

Prefer struct_size() over open-coded versions of idiom:

sizeof(struct-with-flex-array) + sizeof(typeof-flex-array-elements) * count

where count is the max number of items the flexible array is supposed to contain.

In this particular case, in the open-coded version sizeof(typeof-flex-array-elements) is implicit in _count_ because the type of the flex array data is u8:

drivers/net/wireless/broadcom/brcm80211/brcmfmac/fwil_types.h:941:
941 struct brcmf_dload_data_le {

 942         __le16 flag;
 943         __le16 dload_type;
 944         __le32 len;
 945         __le32 crc;
 946         u8 data[];

947 };

---
 drivers/net/wireless/broadcom/brcm80211/brcmfmac/common.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

index 2e836566e218..4a309e5a5707 100644
@@ -110,9 +110,9 @@ static int brcmf_c_download(struct brcmf_if *ifp, u16 flag,
 	dload_buf->dload_type = cpu_to_le16(DL_TYPE_CLM);
 	dload_buf->len = cpu_to_le32(len);
 	dload_buf->crc = cpu_to_le32(0);
-	len = sizeof(*dload_buf) + len;
 
-	err = brcmf_fil_iovar_data_set(ifp, "clmload", dload_buf, len);
+	err = brcmf_fil_iovar_data_set(ifp, "clmload", dload_buf,
+				       struct_size(dload_buf, data, len));
 
 	return err;
 }

@@ -139,7 +139,8 @@ static int brcmf_c_process_clm_blob(struct brcmf_if *ifp)
 		return 0;
 	}
 
-	chunk_buf = kzalloc(sizeof(*chunk_buf) + MAX_CHUNK_LEN, GFP_KERNEL);
+	chunk_buf = kzalloc(struct_size(chunk_buf, data, MAX_CHUNK_LEN),
+			    GFP_KERNEL);
 	if (!chunk_buf) {
 		err = -ENOMEM;
 		goto done;

2.34.1

Thanks for the reviews! :)

--
Gustavo

2 patches applied to wireless-next.git, thanks.

0001650b3d89 wifi: brcmfmac: replace one-element array with flexible-array member in struct brcmf_dload_data_le 633a9b6f514c wifi: brcmfmac: Use struct_size() in code ralated to struct brcmf_dload_data_le

https://patchwork.kernel.org/project/linux-wireless/patch/905f5b68cf93c812360d081caae5b15221db09b6.1668548907.git.gustavoars@kernel.org/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches