* [PATCH][next] prism54: Replace zero-length array with flexible-array member
@ 2020-02-25 1:20 Gustavo A. R. Silva
2020-02-25 18:32 ` Luis Chamberlain
0 siblings, 1 reply; 3+ messages in thread
From: Gustavo A. R. Silva @ 2020-02-25 1:20 UTC (permalink / raw)
To: Luis Chamberlain, Kalle Valo, David S. Miller
Cc: linux-wireless, netdev, linux-kernel, Gustavo A. R. Silva
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/net/wireless/intersil/prism54/isl_oid.h | 8 ++++----
drivers/net/wireless/intersil/prism54/islpci_mgt.h | 2 +-
2 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/drivers/net/wireless/intersil/prism54/isl_oid.h b/drivers/net/wireless/intersil/prism54/isl_oid.h
index 5441c1f9f2fc..1afc2ccf94ca 100644
--- a/drivers/net/wireless/intersil/prism54/isl_oid.h
+++ b/drivers/net/wireless/intersil/prism54/isl_oid.h
@@ -37,7 +37,7 @@ struct obj_mlmeex {
u16 state;
u16 code;
u16 size;
- u8 data[0];
+ u8 data[];
} __packed;
struct obj_buffer {
@@ -68,12 +68,12 @@ struct obj_bss {
struct obj_bsslist {
u32 nr;
- struct obj_bss bsslist[0];
+ struct obj_bss bsslist[];
} __packed;
struct obj_frequencies {
u16 nr;
- u16 mhz[0];
+ u16 mhz[];
} __packed;
struct obj_attachment {
@@ -81,7 +81,7 @@ struct obj_attachment {
char reserved;
short id;
short size;
- char data[0];
+ char data[];
} __packed;
/*
diff --git a/drivers/net/wireless/intersil/prism54/islpci_mgt.h b/drivers/net/wireless/intersil/prism54/islpci_mgt.h
index d6bbbac46b4a..1f87d0aea60c 100644
--- a/drivers/net/wireless/intersil/prism54/islpci_mgt.h
+++ b/drivers/net/wireless/intersil/prism54/islpci_mgt.h
@@ -99,7 +99,7 @@ struct islpci_mgmtframe {
pimfor_header_t *header; /* payload header, points into buf */
void *data; /* payload ex header, points into buf */
struct work_struct ws; /* argument for schedule_work() */
- char buf[0]; /* fragment buffer */
+ char buf[]; /* fragment buffer */
};
int
--
2.25.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH][next] prism54: Replace zero-length array with flexible-array member
2020-02-25 1:20 [PATCH][next] prism54: Replace zero-length array with flexible-array member Gustavo A. R. Silva
@ 2020-02-25 18:32 ` Luis Chamberlain
2020-03-23 17:10 ` drivers/net/wireless spring cleaning Kalle Valo
0 siblings, 1 reply; 3+ messages in thread
From: Luis Chamberlain @ 2020-02-25 18:32 UTC (permalink / raw)
To: Gustavo A. R. Silva
Cc: Kalle Valo, David S. Miller, linux-wireless, netdev, linux-kernel
On Mon, Feb 24, 2020 at 07:20:08PM -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>
I'd rather we just remove this driver completely, as it has a
replacement upstream p54, and remained upstream just for a theoretical
period of time someone was not able to use p54 anymore. I'll follow up
with a removal of the driver.
Luis
^ permalink raw reply [flat|nested] 3+ messages in thread
* drivers/net/wireless spring cleaning
2020-02-25 18:32 ` Luis Chamberlain
@ 2020-03-23 17:10 ` Kalle Valo
0 siblings, 0 replies; 3+ messages in thread
From: Kalle Valo @ 2020-03-23 17:10 UTC (permalink / raw)
To: Luis Chamberlain
Cc: Gustavo A. R. Silva, David S. Miller, linux-wireless, netdev,
linux-kernel
(changing the subject)
Luis Chamberlain <mcgrof@kernel.org> writes:
> On Mon, Feb 24, 2020 at 07:20:08PM -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>
>
> I'd rather we just remove this driver completely, as it has a
> replacement upstream p54, and remained upstream just for a theoretical
> period of time someone was not able to use p54 anymore. I'll follow up
> with a removal of the driver.
Yeah, please do.
I wonder if we should do other spring cleanup as well and remove drivers
like ray_cs and wl3501, I have not seen any activity on those for years.
Also rndis_wlan would be other candidate for removal.
Anyone know if these drivers are used or if they even work anymore?
--
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
^ permalink raw reply [flat|nested] 3+ messages in thread
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