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wifi: at76c50x: prefer struct_size over open coded arithmetic

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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@outlook.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://msgid.link/AS8PR02MB7237578654CEDDFE5F8C17BA8BFE2@AS8PR02MB7237.eurprd02.prod.outlook.com
This commit is contained in:
Erick Archer 2024-06-02 18:13:10 +02:00 committed by Kalle Valo
parent aea9165ccf
commit bbef1d006c
2 changed files with 7 additions and 7 deletions
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12
drivers/net/wireless/atmel/at76c50x-usb.c
View File

@ -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;
}

2
drivers/net/wireless/atmel/at76c50x-usb.h
View File

@ -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 */