There is a regular need in the kernel to provide a way to declare having
a dynamically sized set of trailing elements in a structure. Kernel code
should always use “flexible array members”[1] for these cases. The older
style of one-element or zero-length arrays should no longer be used[2].
This helps with the ongoing efforts to globally enable -Warray-bounds
and get us closer to being able to tighten the FORTIFY_SOURCE routines
on memcpy().
This issue was found with the help of Coccinelle and audited and fixed,
manually.
[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays
Link: https://github.com/KSPP/linux/issues/79
Link: https://github.com/KSPP/linux/issues/109
Signed-off-by: Gustavo A. R. Silva <[email protected]>
---
drivers/net/wireless/marvell/mwifiex/usb.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/wireless/marvell/mwifiex/usb.h b/drivers/net/wireless/marvell/mwifiex/usb.h
index d822ec15b7e6..61a96b7fbf21 100644
--- a/drivers/net/wireless/marvell/mwifiex/usb.h
+++ b/drivers/net/wireless/marvell/mwifiex/usb.h
@@ -134,7 +134,7 @@ struct fw_sync_header {
struct fw_data {
struct fw_header fw_hdr;
__le32 seq_num;
- u8 data[1];
+ u8 data[];
} __packed;
#endif /*_MWIFIEX_USB_H */
--
2.27.0
On Mon, Aug 9, 2021 at 2:08 PM Gustavo A. R. Silva
<[email protected]> wrote:
>
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use “flexible array members”[1] for these cases. The older
> style of one-element or zero-length arrays should no longer be used[2].
>
> This helps with the ongoing efforts to globally enable -Warray-bounds
> and get us closer to being able to tighten the FORTIFY_SOURCE routines
> on memcpy().
>
> This issue was found with the help of Coccinelle and audited and fixed,
> manually.
>
> [1] https://en.wikipedia.org/wiki/Flexible_array_member
> [2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays
>
> Link: https://github.com/KSPP/linux/issues/79
> Link: https://github.com/KSPP/linux/issues/109
> Signed-off-by: Gustavo A. R. Silva <[email protected]>
An important part of your patch rationale should include determining
that the 1-length wasn't actually important anywhere. I double checked
for you, and nobody seemed to be relying on 'sizeof struct fw_data' at
all, so this should be OK:
Reviewed-by: Brian Norris <[email protected]>
On 8/9/21 16:24, Brian Norris wrote:
> On Mon, Aug 9, 2021 at 2:08 PM Gustavo A. R. Silva
> <[email protected]> wrote:
>>
>> There is a regular need in the kernel to provide a way to declare having
>> a dynamically sized set of trailing elements in a structure. Kernel code
>> should always use “flexible array members”[1] for these cases. The older
>> style of one-element or zero-length arrays should no longer be used[2].
>>
>> This helps with the ongoing efforts to globally enable -Warray-bounds
>> and get us closer to being able to tighten the FORTIFY_SOURCE routines
>> on memcpy().
>>
>> This issue was found with the help of Coccinelle and audited and fixed,
>> manually.
>>
>> [1] https://en.wikipedia.org/wiki/Flexible_array_member
>> [2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays
>>
>> Link: https://github.com/KSPP/linux/issues/79
>> Link: https://github.com/KSPP/linux/issues/109
>> Signed-off-by: Gustavo A. R. Silva <[email protected]>
>
> An important part of your patch rationale should include determining
> that the 1-length wasn't actually important anywhere. I double checked
> for you, and nobody seemed to be relying on 'sizeof struct fw_data' at
> all, so this should be OK:
I always do that. That's the reason why I included this line in the
changelog text:
"This issue was found with the help of Coccinelle and audited and fixed,
manually."
Thanks for double-checking, though. :)
> Reviewed-by: Brian Norris <[email protected]>
Thanks
--
Gustavo
"Gustavo A. R. Silva" <[email protected]> wrote:
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use “flexible array members”[1] for these cases. The older
> style of one-element or zero-length arrays should no longer be used[2].
>
> This helps with the ongoing efforts to globally enable -Warray-bounds
> and get us closer to being able to tighten the FORTIFY_SOURCE routines
> on memcpy().
>
> This issue was found with the help of Coccinelle and audited and fixed,
> manually.
>
> [1] https://en.wikipedia.org/wiki/Flexible_array_member
> [2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays
>
> Link: https://github.com/KSPP/linux/issues/79
> Link: https://github.com/KSPP/linux/issues/109
> Signed-off-by: Gustavo A. R. Silva <[email protected]>
> Reviewed-by: Brian Norris <[email protected]>
Patch applied to wireless-drivers-next.git, thanks.
090f2c5d3d07 mwifiex: usb: Replace one-element array with flexible-array member
--
https://patchwork.kernel.org/project/linux-wireless/patch/20210809211134.GA22488@embeddedor/
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches