lkml.org 
[lkml]   [2020]   [Feb]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH] w1_netlink.h: 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.

[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/w1/w1_netlink.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/w1/w1_netlink.h b/drivers/w1/w1_netlink.h
index 3041092e84b3..449680a61569 100644
--- a/drivers/w1/w1_netlink.h
+++ b/drivers/w1/w1_netlink.h
@@ -73,7 +73,7 @@ struct w1_netlink_msg
__u32 res;
} mst;
} id;
- __u8 data[0];
+ __u8 data[];
};

/**
@@ -122,7 +122,7 @@ struct w1_netlink_cmd
__u8 cmd;
__u8 res;
__u16 len;
- __u8 data[0];
+ __u8 data[];
};

#ifdef __KERNEL__
--
2.25.0
\
 
 \ /
  Last update: 2020-02-27 21:20    [W:0.106 / U:4.156 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site