* [PATCH] Input: goldfish_events - Replace zero-length array with flexible-array member
@ 2020-02-13 0:24 Gustavo A. R. Silva
2020-02-14 0:57 ` Dmitry Torokhov
0 siblings, 1 reply; 2+ messages in thread
From: Gustavo A. R. Silva @ 2020-02-13 0:24 UTC (permalink / raw)
To: Dmitry Torokhov; +Cc: linux-input, 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/input/keyboard/goldfish_events.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/input/keyboard/goldfish_events.c b/drivers/input/keyboard/goldfish_events.c
index bc8c85a52a10..57d435fc5c73 100644
--- a/drivers/input/keyboard/goldfish_events.c
+++ b/drivers/input/keyboard/goldfish_events.c
@@ -30,7 +30,7 @@ struct event_dev {
struct input_dev *input;
int irq;
void __iomem *addr;
- char name[0];
+ char name[];
};
static irqreturn_t events_interrupt(int irq, void *dev_id)
--
2.23.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] Input: goldfish_events - Replace zero-length array with flexible-array member
2020-02-13 0:24 [PATCH] Input: goldfish_events - Replace zero-length array with flexible-array member Gustavo A. R. Silva
@ 2020-02-14 0:57 ` Dmitry Torokhov
0 siblings, 0 replies; 2+ messages in thread
From: Dmitry Torokhov @ 2020-02-14 0:57 UTC (permalink / raw)
To: Gustavo A. R. Silva; +Cc: linux-input, linux-kernel
On Wed, Feb 12, 2020 at 06:24:30PM -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>
Applied, thank you.
> ---
> drivers/input/keyboard/goldfish_events.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/input/keyboard/goldfish_events.c b/drivers/input/keyboard/goldfish_events.c
> index bc8c85a52a10..57d435fc5c73 100644
> --- a/drivers/input/keyboard/goldfish_events.c
> +++ b/drivers/input/keyboard/goldfish_events.c
> @@ -30,7 +30,7 @@ struct event_dev {
> struct input_dev *input;
> int irq;
> void __iomem *addr;
> - char name[0];
> + char name[];
> };
>
> static irqreturn_t events_interrupt(int irq, void *dev_id)
> --
> 2.23.0
>
--
Dmitry
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