* [PATCH][next] net: cisco: Replace zero-length array with flexible-array member
@ 2020-02-25 0:18 Gustavo A. R. Silva
2020-02-27 0:46 ` David Miller
0 siblings, 1 reply; 3+ messages in thread
From: Gustavo A. R. Silva @ 2020-02-25 0:18 UTC (permalink / raw)
To: Christian Benvenuti, Govindarajulu Varadarajan, Parvi Kaustubhi,
David S. Miller
Cc: 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]
Lastly, fix the following checkpatch warning:
CHECK: Prefer kernel type 'u32' over 'u_int32_t'
#61: FILE: drivers/net/ethernet/cisco/enic/vnic_devcmd.h:653:
+ u_int32_t val[];
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/ethernet/cisco/enic/vnic_devcmd.h | 8 ++++----
drivers/net/ethernet/cisco/enic/vnic_vic.h | 2 +-
2 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/drivers/net/ethernet/cisco/enic/vnic_devcmd.h b/drivers/net/ethernet/cisco/enic/vnic_devcmd.h
index fef5a0a0663d..fcc4a3ccdd94 100644
--- a/drivers/net/ethernet/cisco/enic/vnic_devcmd.h
+++ b/drivers/net/ethernet/cisco/enic/vnic_devcmd.h
@@ -541,7 +541,7 @@ struct vnic_devcmd_notify {
struct vnic_devcmd_provinfo {
u8 oui[3];
u8 type;
- u8 data[0];
+ u8 data[];
};
/* These are used in flags field of different filters to denote
@@ -648,9 +648,9 @@ enum {
#define FILTER_MAX_BUF_SIZE 100
struct filter_tlv {
- u_int32_t type;
- u_int32_t length;
- u_int32_t val[0];
+ u32 type;
+ u32 length;
+ u32 val[];
};
enum {
diff --git a/drivers/net/ethernet/cisco/enic/vnic_vic.h b/drivers/net/ethernet/cisco/enic/vnic_vic.h
index 9ef81f148351..057776908828 100644
--- a/drivers/net/ethernet/cisco/enic/vnic_vic.h
+++ b/drivers/net/ethernet/cisco/enic/vnic_vic.h
@@ -59,7 +59,7 @@ struct vic_provinfo {
u16 type;
u16 length;
u8 value[0];
- } tlv[0];
+ } tlv[];
} __packed;
#define VIC_PROVINFO_ADD_TLV(vp, tlvtype, tlvlen, data) \
--
2.25.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH][next] net: cisco: Replace zero-length array with flexible-array member
2020-02-25 0:18 [PATCH][next] net: cisco: Replace zero-length array with flexible-array member Gustavo A. R. Silva
@ 2020-02-27 0:46 ` David Miller
2020-02-27 0:53 ` Gustavo A. R. Silva
0 siblings, 1 reply; 3+ messages in thread
From: David Miller @ 2020-02-27 0:46 UTC (permalink / raw)
To: gustavo; +Cc: benve, _govind, pkaustub, netdev, linux-kernel
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Mon, 24 Feb 2020 18:18:26 -0600
> 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]
>
> Lastly, fix the following checkpatch warning:
> CHECK: Prefer kernel type 'u32' over 'u_int32_t'
> #61: FILE: drivers/net/ethernet/cisco/enic/vnic_devcmd.h:653:
> + u_int32_t val[];
>
> 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.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH][next] net: cisco: Replace zero-length array with flexible-array member
2020-02-27 0:46 ` David Miller
@ 2020-02-27 0:53 ` Gustavo A. R. Silva
0 siblings, 0 replies; 3+ messages in thread
From: Gustavo A. R. Silva @ 2020-02-27 0:53 UTC (permalink / raw)
To: David Miller; +Cc: benve, _govind, pkaustub, netdev, linux-kernel
On 2/26/20 18:46, David Miller wrote:
>>
>> [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.
>
Thanks, Dave.
--
Gustavo
^ permalink raw reply [flat|nested] 3+ messages in thread
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