brcmfmac: Replace zero-length array with flexible-array member
PATCH 1/1 brcmfmac: Replace zero-length array with flexible-array member
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]
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")
--- drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.h | 2 +- drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)
drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.h +1 -1
@@ -60,7 +60,7 @@ struct brcmf_fw_request {u16 bus_nr;u32 n_items;const char *board_type; -struct brcmf_fw_item items[0 ]; +struct brcmf_fw_item items[]; };struct brcmf_fw_name {
drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c +1 -1
@@ -32,7 +32,7 @@ struct brcmf_fweh_queue_item {u8 ifaddr[ETH_ALEN ];struct brcmf_event_msg_be emsg;u32 datalen; -u8 data[0 ]; +u8 data[]; };/**
Signature · 1 line
2.25.0
Quoted 4 lines · Gustavo A. R. Silva
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:
[...]
Quoted 9 lines
"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]
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] commit76497732932f("cxgb3/l2t: Fix undefined behaviour")
Quoted 5 lines
Signed-off-by Gustavo A. R. Silva <[email protected]>--- drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.h | 2 +- drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)
Quoted 22 lines · Gustavo A. R. Silva
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]
Quoted 8 lines
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] commit76497732932f("cxgb3/l2t: Fix undefined behaviour")Signed-off-by Gustavo A. R. Silva <[email protected]>Acked-by Arend van Spriel <[email protected]>
Patch applied to wireless-drivers-next.git, thanks.
232c897eb5ca brcmfmac: Replace zero-length array with flexible-array member
Signature · 3 lines
https://patchwork.kernel.org/patch/11402413/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches