| Message ID | 20200214172132.GA28389@embeddedor (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | 3dbae15538972c9e1578cb216964c2840361a538 |
| Headers | show |
| Series | Input: cyapa - replace zero-length array with flexible-array member | expand |
On Fri, Feb 14, 2020 at 11:21:32AM -0600, 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: > > 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> Applied, thank you. > --- > drivers/input/mouse/cyapa_gen5.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/input/mouse/cyapa_gen5.c b/drivers/input/mouse/cyapa_gen5.c > index 14239fbd72cf..7f012bfa2658 100644 > --- a/drivers/input/mouse/cyapa_gen5.c > +++ b/drivers/input/mouse/cyapa_gen5.c > @@ -250,7 +250,7 @@ struct cyapa_tsg_bin_image_data_record { > > struct cyapa_tsg_bin_image { > struct cyapa_tsg_bin_image_head image_head; > - struct cyapa_tsg_bin_image_data_record records[0]; > + struct cyapa_tsg_bin_image_data_record records[]; > } __packed; > > struct pip_bl_packet_start { > @@ -271,7 +271,7 @@ struct pip_bl_cmd_head { > u8 report_id; /* Bootloader output report id, must be 40h */ > u8 rsvd; /* Reserved, must be 0 */ > struct pip_bl_packet_start packet_start; > - u8 data[0]; /* Command data variable based on commands */ > + u8 data[]; /* Command data variable based on commands */ > } __packed; > > /* Initiate bootload command data structure. */ > @@ -300,7 +300,7 @@ struct tsg_bl_metadata_row_params { > struct tsg_bl_flash_row_head { > u8 flash_array_id; > __le16 flash_row_id; > - u8 flash_data[0]; > + u8 flash_data[]; > } __packed; > > struct pip_app_cmd_head { > @@ -314,7 +314,7 @@ struct pip_app_cmd_head { > * Bit 6-0: command code. > */ > u8 cmd_code; > - u8 parameter_data[0]; /* Parameter data variable based on cmd_code */ > + u8 parameter_data[]; /* Parameter data variable based on cmd_code */ > } __packed; > > /* Application get/set parameter command data structure */ > -- > 2.25.0 >
diff --git a/drivers/input/mouse/cyapa_gen5.c b/drivers/input/mouse/cyapa_gen5.c index 14239fbd72cf..7f012bfa2658 100644 --- a/drivers/input/mouse/cyapa_gen5.c +++ b/drivers/input/mouse/cyapa_gen5.c @@ -250,7 +250,7 @@ struct cyapa_tsg_bin_image_data_record { struct cyapa_tsg_bin_image { struct cyapa_tsg_bin_image_head image_head; - struct cyapa_tsg_bin_image_data_record records[0]; + struct cyapa_tsg_bin_image_data_record records[]; } __packed; struct pip_bl_packet_start { @@ -271,7 +271,7 @@ struct pip_bl_cmd_head { u8 report_id; /* Bootloader output report id, must be 40h */ u8 rsvd; /* Reserved, must be 0 */ struct pip_bl_packet_start packet_start; - u8 data[0]; /* Command data variable based on commands */ + u8 data[]; /* Command data variable based on commands */ } __packed; /* Initiate bootload command data structure. */ @@ -300,7 +300,7 @@ struct tsg_bl_metadata_row_params { struct tsg_bl_flash_row_head { u8 flash_array_id; __le16 flash_row_id; - u8 flash_data[0]; + u8 flash_data[]; } __packed; struct pip_app_cmd_head { @@ -314,7 +314,7 @@ struct pip_app_cmd_head { * Bit 6-0: command code. */ u8 cmd_code; - u8 parameter_data[0]; /* Parameter data variable based on cmd_code */ + u8 parameter_data[]; /* Parameter data variable based on cmd_code */ } __packed; /* Application get/set parameter command data structure */
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/input/mouse/cyapa_gen5.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)