libertas: Replace zero-length array with flexible-array member
Subsystems (3)
PATCH 1/1 libertas: 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/marvell/libertas/host.h | 4 ++-- drivers/net/wireless/marvell/libertas/if_sdio.c | 2 +- drivers/net/wireless/marvell/libertas/if_spi.c | 2 +- drivers/net/wireless/marvell/libertas/if_usb.h | 2 +- 4 files changed, 5 insertions(+), 5 deletions(-)
drivers/net/wireless/marvell/libertas/host.h +2 -2
@@ -461,7 +461,7 @@ struct cmd_ds_802_11_scan {uint8_t bsstype;uint8_t bssid[ETH_ALEN ]; -uint8_t tlvbuffer[0 ]; +uint8_t tlvbuffer[]; } __packed;struct cmd_ds_802_11_scan_rsp {
@@ -469,7 +469,7 @@ struct cmd_ds_802_11_scan_rsp {__le16 bssdescriptsize;uint8_t nr_sets; -uint8_t bssdesc_and_tlvbuffer[0 ]; +uint8_t bssdesc_and_tlvbuffer[]; } __packed;struct cmd_ds_802_11_get_log {
drivers/net/wireless/marvell/libertas/if_sdio.c +1 -1
@@ -103,7 +103,7 @@ MODULE_FIRMWARE("sd8688.bin");struct if_sdio_packet {struct if_sdio_packet *next;u16 nb; -u8 buffer[0 ] __attribute__((aligned (4 ))); +u8 buffer[]__aligned(4) ; };struct if_sdio_card {
drivers/net/wireless/marvell/libertas/if_spi.c +1 -1
@@ -35,7 +35,7 @@struct if_spi_packet {struct list_head list;u16 blen; -u8 buffer[0 ] __attribute__((aligned (4 ))); +u8 buffer[]__aligned(4) ; };struct if_spi_card {
drivers/net/wireless/marvell/libertas/if_usb.h +1 -1
@@ -91,7 +91,7 @@ struct fwheader {struct fwdata {struct fwheader hdr;__le32 seqnum; -uint8_t data[0 ]; +uint8_t data[]; };/* fwsyncheader */
Signature · 1 line
2.25.0
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 7 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]>
Patch applied to wireless-drivers-next.git, thanks.
c5047d5b831b libertas: Replace zero-length array with flexible-array member
Signature · 3 lines
https://patchwork.kernel.org/patch/11402377/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches