intel: 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>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/intel/fm10k/fm10k.h b/drivers/net/ethernet/intel/fm10k/fm10k.h
index f306084..5b78362 100644 (file)
--- a/drivers/net/ethernet/intel/fm10k/fm10k.h
+++ b/drivers/net/ethernet/intel/fm10k/fm10k.h
@@ -41,7 +41,7 @@ struct fm10k_l2_accel {
        u16 count;
        u16 dglort;
        struct rcu_head rcu;
-       struct net_device *macvlan[0];
+       struct net_device *macvlan[];
 };
 
 enum fm10k_ring_state_t {
@@ -198,7 +198,7 @@ struct fm10k_q_vector {
        struct rcu_head rcu;    /* to avoid race with update stats on free */
 
        /* for dynamic allocation of rings associated with this q_vector */
-       struct fm10k_ring ring[0] ____cacheline_internodealigned_in_smp;
+       struct fm10k_ring ring[] ____cacheline_internodealigned_in_smp;
 };
 
 enum fm10k_ring_f_enum {
@@ -218,7 +218,7 @@ struct fm10k_iov_data {
        unsigned int            num_vfs;
        unsigned int            next_vf_mbx;
        struct rcu_head         rcu;
-       struct fm10k_vf_info    vf_info[0];
+       struct fm10k_vf_info    vf_info[];
 };
 
 struct fm10k_udp_port {

diff --git a/drivers/net/ethernet/intel/i40e/i40e.h b/drivers/net/ethernet/intel/i40e/i40e.h
index 4833187..e95b8da 100644 (file)
--- a/drivers/net/ethernet/intel/i40e/i40e.h
+++ b/drivers/net/ethernet/intel/i40e/i40e.h
@@ -334,13 +334,13 @@ int i40e_ddp_flash(struct net_device *netdev, struct ethtool_flash *flash);
 
 struct i40e_ddp_profile_list {
        u32 p_count;
-       struct i40e_profile_info p_info[0];
+       struct i40e_profile_info p_info[];
 };
 
 struct i40e_ddp_old_profile_list {
        struct list_head list;
        size_t old_ddp_size;
-       u8 old_ddp_buf[0];
+       u8 old_ddp_buf[];
 };
 
 /* macros related to FLX_PIT */

diff --git a/drivers/net/ethernet/intel/igb/igb.h b/drivers/net/ethernet/intel/igb/igb.h
index 49b5fa9..0c9282e 100644 (file)
--- a/drivers/net/ethernet/intel/igb/igb.h
+++ b/drivers/net/ethernet/intel/igb/igb.h
@@ -306,7 +306,7 @@ struct igb_q_vector {
        char name[IFNAMSIZ + 9];
 
        /* for dynamic allocation of rings associated with this q_vector */
-       struct igb_ring ring[0] ____cacheline_internodealigned_in_smp;
+       struct igb_ring ring[] ____cacheline_internodealigned_in_smp;
 };
 
 enum e1000_ring_flags_t {

diff --git a/drivers/net/ethernet/intel/igc/igc.h b/drivers/net/ethernet/intel/igc/igc.h
index 0014828..a1f845a 100644 (file)
--- a/drivers/net/ethernet/intel/igc/igc.h
+++ b/drivers/net/ethernet/intel/igc/igc.h
@@ -326,7 +326,7 @@ struct igc_q_vector {
        struct net_device poll_dev;
 
        /* for dynamic allocation of rings associated with this q_vector */
-       struct igc_ring ring[0] ____cacheline_internodealigned_in_smp;
+       struct igc_ring ring[] ____cacheline_internodealigned_in_smp;
 };
 
 #define MAX_ETYPE_FILTER               (4 - 1)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe.h b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
index 39e73ad..2833e4f 100644 (file)
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe.h
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
@@ -462,7 +462,7 @@ struct ixgbe_q_vector {
        char name[IFNAMSIZ + 9];
 
        /* for dynamic allocation of rings associated with this q_vector */
-       struct ixgbe_ring ring[0] ____cacheline_internodealigned_in_smp;
+       struct ixgbe_ring ring[] ____cacheline_internodealigned_in_smp;
 };
 
 #ifdef CONFIG_IXGBE_HWMON