From: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
[ Upstream commit 08ca27d027c238ed3f9b9968d349cebde44d99a6 ]
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@xxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Stable-dep-of: ed779fe4c9b5 ("neighbour: fix unaligned access to pneigh_entry")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
include/net/neighbour.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/net/neighbour.h b/include/net/neighbour.h
index b6494e87c897c..729bdf710b7e0 100644
--- a/include/net/neighbour.h
+++ b/include/net/neighbour.h
@@ -174,7 +174,7 @@ struct pneigh_entry {
struct net_device *dev;
u8 flags;
u8 protocol;
- u8 key[0];
+ u8 key[];
};
/*
--
2.39.2
