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[next] mwifiex: usb: Replace one-element array with flexible-array member

Message ID 20210809211134.GA22488@embeddedor (mailing list archive)
State Awaiting Upstream
Delegated to: Netdev Maintainers
Headers show
Series [next] mwifiex: usb: Replace one-element array with flexible-array member | expand

Checks

Context Check Description
netdev/tree_selection success Not a local patch

Commit Message

Gustavo A. R. Silva Aug. 9, 2021, 9:11 p.m. UTC
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 <gustavoars@kernel.org>
---
 drivers/net/wireless/marvell/mwifiex/usb.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Brian Norris Aug. 9, 2021, 9:24 p.m. UTC | #1
On Mon, Aug 9, 2021 at 2:08 PM Gustavo A. R. Silva
<gustavoars@kernel.org> 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 <gustavoars@kernel.org>

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 <briannorris@chromium.org>
Gustavo A. R. Silva Aug. 9, 2021, 9:32 p.m. UTC | #2
On 8/9/21 16:24, Brian Norris wrote:
> On Mon, Aug 9, 2021 at 2:08 PM Gustavo A. R. Silva
> <gustavoars@kernel.org> 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 <gustavoars@kernel.org>
> 
> 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 <briannorris@chromium.org>

Thanks
--
Gustavo
Kalle Valo Aug. 21, 2021, 5:50 p.m. UTC | #3
"Gustavo A. R. Silva" <gustavoars@kernel.org> 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 <gustavoars@kernel.org>
> Reviewed-by: Brian Norris <briannorris@chromium.org>

Patch applied to wireless-drivers-next.git, thanks.

090f2c5d3d07 mwifiex: usb: Replace one-element array with flexible-array member
diff mbox series

Patch

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 */