cxgb3/l2t: Fix undefined behaviour

BugLink: https://bugs.launchpad.net/bugs/1838700
[ Upstream commit 76497732932f15e7323dc805e8ea8dc11bb587cf ]

The use of zero-sized array causes undefined behaviour when it is not
the last member in a structure. As it happens to be in this case.

Also, the current code makes use of a language extension to the C90
standard, but the preferred mechanism to declare variable-length
types such as this one is a flexible array member, 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. Which is beneficial
to cultivate a high-quality code.

Fixes: e48f129c2f20 ("[SCSI] cxgb3i: convert cdev->l2opt to use rcu to prevent NULL dereference")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/net/ethernet/chelsio/cxgb3/l2t.h b/drivers/net/ethernet/chelsio/cxgb3/l2t.h
index c2fd323c4078284ac84aa58825cc84958f108fe8..ea75f275023ffad95a4e2dfa46b1db51935417d8 100644 (file)
--- a/drivers/net/ethernet/chelsio/cxgb3/l2t.h
+++ b/drivers/net/ethernet/chelsio/cxgb3/l2t.h
@@ -75,8 +75,8 @@ struct l2t_data {
        struct l2t_entry *rover;        /* starting point for next allocation */
        atomic_t nfree;         /* number of free entries */
        rwlock_t lock;
-       struct l2t_entry l2tab[0];
        struct rcu_head rcu_head;       /* to handle rcu cleanup */
+       struct l2t_entry l2tab[];
 };
 
 typedef void (*arp_failure_handler_func)(struct t3cdev * dev,