[lkml]   [2020]   [Mar]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH][next] net: mip6: Replace zero-length array with flexible-array member
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.

[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <>
include/net/mip6.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/mip6.h b/include/net/mip6.h
index f1c28971c362..67cd7e50804c 100644
--- a/include/net/mip6.h
+++ b/include/net/mip6.h
@@ -25,7 +25,7 @@ struct ip6_mh {
__u8 ip6mh_reserved;
__u16 ip6mh_cksum;
/* Followed by type specific messages */
- __u8 data[0];
+ __u8 data[];
} __packed;

#define IP6_MH_TYPE_BRR 0 /* Binding Refresh Request */
 \ /
  Last update: 2020-03-02 12:58    [W:0.097 / U:22.428 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site