| Message ID | 20200225011415.GA31868@embeddedor (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 645aa87fdfd9e608faba215677d92de9dba6dc22 |
| Delegated to: | Kalle Valo |
| Headers | show |
| Series | [next] orinoco: 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. 645aa87fdfd9 orinoco: Replace zero-length array with flexible-array member
diff --git a/drivers/net/wireless/intersil/orinoco/fw.c b/drivers/net/wireless/intersil/orinoco/fw.c index 400a35217644..015af782881b 100644 --- a/drivers/net/wireless/intersil/orinoco/fw.c +++ b/drivers/net/wireless/intersil/orinoco/fw.c @@ -49,7 +49,7 @@ struct orinoco_fw_header { __le32 pdr_offset; /* Offset to PDR data from eof header */ __le32 pri_offset; /* Offset to primary plug data */ __le32 compat_offset; /* Offset to compatibility data*/ - char signature[0]; /* FW signature length headersize-20 */ + char signature[]; /* FW signature length headersize-20 */ } __packed; /* Check the range of various header entries. Return a pointer to a diff --git a/drivers/net/wireless/intersil/orinoco/hermes.h b/drivers/net/wireless/intersil/orinoco/hermes.h index 121fdd8e5da2..9f668185b7d2 100644 --- a/drivers/net/wireless/intersil/orinoco/hermes.h +++ b/drivers/net/wireless/intersil/orinoco/hermes.h @@ -341,7 +341,7 @@ struct agere_ext_scan_info { __le64 timestamp; __le16 beacon_interval; __le16 capabilities; - u8 data[0]; + u8 data[]; } __packed; #define HERMES_LINKSTATUS_NOT_CONNECTED (0x0000) diff --git a/drivers/net/wireless/intersil/orinoco/hermes_dld.c b/drivers/net/wireless/intersil/orinoco/hermes_dld.c index 4a10b7aca043..dbeadfcfefe2 100644 --- a/drivers/net/wireless/intersil/orinoco/hermes_dld.c +++ b/drivers/net/wireless/intersil/orinoco/hermes_dld.c @@ -64,7 +64,7 @@ struct dblock { __le32 addr; /* adapter address where to write the block */ __le16 len; /* length of the data only, in bytes */ - char data[0]; /* data to be written */ + char data[]; /* data to be written */ } __packed; /* @@ -76,7 +76,7 @@ struct pdr { __le32 id; /* record ID */ __le32 addr; /* adapter address where to write the data */ __le32 len; /* expected length of the data, in bytes */ - char next[0]; /* next PDR starts here */ + char next[]; /* next PDR starts here */ } __packed; /* @@ -87,7 +87,7 @@ struct pdr { struct pdi { __le16 len; /* length of ID and data, in words */ __le16 id; /* record ID */ - char data[0]; /* plug data */ + char data[]; /* plug data */ } __packed; /*** FW data block access functions ***/ diff --git a/drivers/net/wireless/intersil/orinoco/orinoco_usb.c b/drivers/net/wireless/intersil/orinoco/orinoco_usb.c index e753f43e0162..a77bbcd544d6 100644 --- a/drivers/net/wireless/intersil/orinoco/orinoco_usb.c +++ b/drivers/net/wireless/intersil/orinoco/orinoco_usb.c @@ -202,7 +202,7 @@ struct ezusb_packet { __le16 crc; /* CRC up to here */ __le16 hermes_len; __le16 hermes_rid; - u8 data[0]; + u8 data[]; } __packed; /* Table of devices that work or may work with this driver */
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/intersil/orinoco/fw.c | 2 +- drivers/net/wireless/intersil/orinoco/hermes.h | 2 +- drivers/net/wireless/intersil/orinoco/hermes_dld.c | 6 +++--- drivers/net/wireless/intersil/orinoco/orinoco_usb.c | 2 +- 4 files changed, 6 insertions(+), 6 deletions(-)