| Message ID | 20200225020804.GA9428@embeddedor (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 232c897eb5ca21fce241f75b98c78f2cb36af00f |
| Delegated to: | Kalle Valo |
| Headers | show |
| Series | [next] brcmfmac: Replace zero-length array with flexible-array member | expand |
On 2/25/2020 3:08 AM, Gustavo A. R. Silva 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: [...] > "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") Acked-by: Arend van Spriel <arend.vanspriel@broadcom.com> > Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> > --- > 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(-)
"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> > Acked-by: Arend van Spriel <arend.vanspriel@broadcom.com> Patch applied to wireless-drivers-next.git, thanks. 232c897eb5ca brcmfmac: Replace zero-length array with flexible-array member
diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.h b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.h index 3347439543bb..46c66415b4a6 100644 --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.h +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.h @@ -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 { diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c index 79c8a858b6d6..a5cced2c89ac 100644 --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c @@ -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[]; }; /**
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/broadcom/brcm80211/brcmfmac/firmware.h | 2 +- drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)