| Message ID | 20200225011709.GA601@embeddedor (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | c5047d5b831bb5f4dfa22230a2f64794ed20ea82 |
| Delegated to: | Kalle Valo |
| Headers | show |
| Series | [next] libertas: Replace zero-length array with flexible-array member | expand |
"Gustavo A. R. Silva" <gustavo@embeddedor.com> wrote: > 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") > > Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> Patch applied to wireless-drivers-next.git, thanks. c5047d5b831b libertas: Replace zero-length array with flexible-array member
diff --git a/drivers/net/wireless/marvell/libertas/host.h b/drivers/net/wireless/marvell/libertas/host.h index a4fc3f79bb17..dfa22468b14a 100644 --- a/drivers/net/wireless/marvell/libertas/host.h +++ b/drivers/net/wireless/marvell/libertas/host.h @@ -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 { diff --git a/drivers/net/wireless/marvell/libertas/if_sdio.c b/drivers/net/wireless/marvell/libertas/if_sdio.c index 30f1025ecb9b..acf61b93b782 100644 --- a/drivers/net/wireless/marvell/libertas/if_sdio.c +++ b/drivers/net/wireless/marvell/libertas/if_sdio.c @@ -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 { diff --git a/drivers/net/wireless/marvell/libertas/if_spi.c b/drivers/net/wireless/marvell/libertas/if_spi.c index d07fe82c557e..3625baa66d3e 100644 --- a/drivers/net/wireless/marvell/libertas/if_spi.c +++ b/drivers/net/wireless/marvell/libertas/if_spi.c @@ -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 { diff --git a/drivers/net/wireless/marvell/libertas/if_usb.h b/drivers/net/wireless/marvell/libertas/if_usb.h index 8dc14bec3e16..7d0daeb33c3f 100644 --- a/drivers/net/wireless/marvell/libertas/if_usb.h +++ b/drivers/net/wireless/marvell/libertas/if_usb.h @@ -91,7 +91,7 @@ struct fwheader { struct fwdata { struct fwheader hdr; __le32 seqnum; - uint8_t data[0]; + uint8_t data[]; }; /* fwsyncheader */
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") Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> --- 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(-)