This is an effort to get rid of all multiplications from allocation
functions in order to prevent integer overflows [1][2].
As the "cmd_buf" variable is a pointer to "struct at76_command" and
this structure ends in a flexible array:
struct at76_command {
[...]
u8 data[];
} __packed;
the preferred way in the kernel is to use the struct_size() helper to
do the arithmetic instead of the calculation "size + count" in the
kmalloc() function.
Also, declare a new variable (total_size) since the return value of the
struct_size() helper is used several times.
At the same time, prepare for the coming implementation by GCC and Clang
of the __counted_by attribute. Flexible array members annotated with
__counted_by can have their accesses bounds-checked at run-time via
CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for
strcpy/memcpy-family functions). In this case, it is important to note
that the attribute used is "__counted_by_le" since the counter type is
"__le16".
This way, the code is more readable and safer.
Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
Link: https://github.com/KSPP/linux/issues/160 [2]
Signed-off-by: Erick Archer <erick.archer@xxxxxxxxxxx>
---
drivers/net/wireless/atmel/at76c50x-usb.c | 12 ++++++------
drivers/net/wireless/atmel/at76c50x-usb.h | 2 +-
2 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/net/wireless/atmel/at76c50x-usb.c b/drivers/net/wireless/atmel/at76c50x-usb.c
index 0ca2f629683d..baa53cfefe48 100644
--- a/drivers/net/wireless/atmel/at76c50x-usb.c
+++ b/drivers/net/wireless/atmel/at76c50x-usb.c
@@ -721,9 +721,11 @@ static int at76_set_card_command(struct usb_device *udev, u8 cmd, void *buf,
int buf_size)
{
int ret;
- struct at76_command *cmd_buf = kmalloc(sizeof(struct at76_command) +
- buf_size, GFP_KERNEL);
+ size_t total_size;
+ struct at76_command *cmd_buf;
+ total_size = struct_size(cmd_buf, data, buf_size);
+ cmd_buf = kmalloc(total_size, GFP_KERNEL);
if (!cmd_buf)
return -ENOMEM;
@@ -732,15 +734,13 @@ static int at76_set_card_command(struct usb_device *udev, u8 cmd, void *buf,
cmd_buf->size = cpu_to_le16(buf_size);
memcpy(cmd_buf->data, buf, buf_size);
- at76_dbg_dump(DBG_CMD, cmd_buf, sizeof(struct at76_command) + buf_size,
+ at76_dbg_dump(DBG_CMD, cmd_buf, total_size,
"issuing command %s (0x%02x)",
at76_get_cmd_string(cmd), cmd);
ret = usb_control_msg(udev, usb_sndctrlpipe(udev, 0), 0x0e,
USB_TYPE_VENDOR | USB_DIR_OUT | USB_RECIP_DEVICE,
- 0, 0, cmd_buf,
- sizeof(struct at76_command) + buf_size,
- USB_CTRL_GET_TIMEOUT);
+ 0, 0, cmd_buf, total_size, USB_CTRL_GET_TIMEOUT);
kfree(cmd_buf);
return ret;
}
diff --git a/drivers/net/wireless/atmel/at76c50x-usb.h b/drivers/net/wireless/atmel/at76c50x-usb.h
index 746e64dfd8aa..843146a0de64 100644
--- a/drivers/net/wireless/atmel/at76c50x-usb.h
+++ b/drivers/net/wireless/atmel/at76c50x-usb.h
@@ -151,7 +151,7 @@ struct at76_command {
u8 cmd;
u8 reserved;
__le16 size;
- u8 data[];
+ u8 data[] __counted_by_le(size);
} __packed;
/* Length of Atmel-specific Rx header before 802.11 frame */
--
2.25.1
