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net: cisco: Replace zero-length array with flexible-array member

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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 7649773293 ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Gustavo A. R. Silva 2020-02-24 18:18:26 -06:00 committed by David S. Miller
parent 274ac2831a
commit d1c73cbdf9
2 changed files with 5 additions and 5 deletions
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8
drivers/net/ethernet/cisco/enic/vnic_devcmd.h
View file

@ -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 {

2
drivers/net/ethernet/cisco/enic/vnic_vic.h
View file

@ -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) \