From: Gustavo A. R. Silva gustavo@embeddedor.com
[ 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@embeddedor.com Signed-off-by: David S. Miller davem@davemloft.net Stable-dep-of: ed779fe4c9b5 ("neighbour: fix unaligned access to pneigh_entry") Signed-off-by: Sasha Levin sashal@kernel.org --- 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[]; };
/*