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>
---
net/core/bpf_sk_storage.c | 2 +-
net/core/devlink.c | 2 +-
net/core/drop_monitor.c | 2 +-
3 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index 3ab23f698221..427cfbc0d50d 100644
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -60,7 +60,7 @@ struct bpf_sk_storage_data {
* the number of cachelines access during the cache hit case.
*/
struct bpf_sk_storage_map __rcu *smap;
- u8 data[0] __aligned(8);
+ u8 data[] __aligned(8);
};
/* Linked to bpf_sk_storage and bpf_sk_storage_map */
diff --git a/net/core/devlink.c b/net/core/devlink.c
index f8af5e2d748b..295d761cbfb1 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -4232,7 +4232,7 @@ struct devlink_fmsg_item {
int attrtype;
u8 nla_type;
u16 len;
- int value[0];
+ int value[];
};
struct devlink_fmsg {
diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index d58c1c45a895..8e33cec9fc4e 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -68,7 +68,7 @@ struct net_dm_hw_entry {
struct net_dm_hw_entries {
u32 num_entries;
- struct net_dm_hw_entry entries[0];
+ struct net_dm_hw_entry entries[];
};
struct per_cpu_dm_data {
--
2.25.0
