| Message ID | 20200218203114.GA27096@embeddedor (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | [next] net/mlx5e: Replace zero-length array with flexible-array member | expand |
On Tue, Feb 18, 2020 at 02:31:14PM -0600, Gustavo A. R. Silva wrote: > 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> > --- > drivers/net/ethernet/mellanox/mlx5/core/en.h | 2 +- > drivers/net/ethernet/mellanox/mlx5/core/fpga/ipsec.c | 2 +- > drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c | 2 +- > drivers/net/ethernet/mellanox/mlx5/core/ipoib/ipoib.h | 4 ++-- > 4 files changed, 5 insertions(+), 5 deletions(-) > Thanks, applied to mlx5-next.
On 2/19/20 01:14, Leon Romanovsky wrote: >> >> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> >> --- >> drivers/net/ethernet/mellanox/mlx5/core/en.h | 2 +- >> drivers/net/ethernet/mellanox/mlx5/core/fpga/ipsec.c | 2 +- >> drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c | 2 +- >> drivers/net/ethernet/mellanox/mlx5/core/ipoib/ipoib.h | 4 ++-- >> 4 files changed, 5 insertions(+), 5 deletions(-) >> > > Thanks, applied to mlx5-next. > Thank you. -- Gustavo
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en.h b/drivers/net/ethernet/mellanox/mlx5/core/en.h index 220ef9f06f84..a960099cd7aa 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/en.h +++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h @@ -204,7 +204,7 @@ struct mlx5e_tx_wqe { struct mlx5e_rx_wqe_ll { struct mlx5_wqe_srq_next_seg next; - struct mlx5_wqe_data_seg data[0]; + struct mlx5_wqe_data_seg data[]; }; struct mlx5e_rx_wqe_cyc { diff --git a/drivers/net/ethernet/mellanox/mlx5/core/fpga/ipsec.c b/drivers/net/ethernet/mellanox/mlx5/core/fpga/ipsec.c index 4c61d25d2e88..b794888fa3ba 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/fpga/ipsec.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/fpga/ipsec.c @@ -57,7 +57,7 @@ struct mlx5_fpga_ipsec_cmd_context { struct completion complete; struct mlx5_fpga_device *dev; struct list_head list; /* Item in pending_cmds */ - u8 command[0]; + u8 command[]; }; struct mlx5_fpga_esp_xfrm; diff --git a/drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c b/drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c index ab69effb056d..f43caefd07a1 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c @@ -470,7 +470,7 @@ struct mlx5_fc_bulk { u32 base_id; int bulk_len; unsigned long *bitmask; - struct mlx5_fc fcs[0]; + struct mlx5_fc fcs[]; }; static void mlx5_fc_init(struct mlx5_fc *counter, struct mlx5_fc_bulk *bulk, diff --git a/drivers/net/ethernet/mellanox/mlx5/core/ipoib/ipoib.h b/drivers/net/ethernet/mellanox/mlx5/core/ipoib/ipoib.h index c87962cab921..de7e01a027bb 100644 --- a/drivers/net/ethernet/mellanox/mlx5/core/ipoib/ipoib.h +++ b/drivers/net/ethernet/mellanox/mlx5/core/ipoib/ipoib.h @@ -56,7 +56,7 @@ struct mlx5i_priv { u32 qkey; u16 pkey_index; struct mlx5i_pkey_qpn_ht *qpn_htbl; - char *mlx5e_priv[0]; + char *mlx5e_priv[]; }; int mlx5i_create_tis(struct mlx5_core_dev *mdev, u32 underlay_qpn, u32 *tisn); @@ -107,7 +107,7 @@ struct mlx5i_tx_wqe { struct mlx5_wqe_datagram_seg datagram; struct mlx5_wqe_eth_pad pad; struct mlx5_wqe_eth_seg eth; - struct mlx5_wqe_data_seg data[0]; + struct mlx5_wqe_data_seg data[]; }; static inline void mlx5i_sq_fetch_wqe(struct mlx5e_txqsq *sq,
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> --- drivers/net/ethernet/mellanox/mlx5/core/en.h | 2 +- drivers/net/ethernet/mellanox/mlx5/core/fpga/ipsec.c | 2 +- drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c | 2 +- drivers/net/ethernet/mellanox/mlx5/core/ipoib/ipoib.h | 4 ++-- 4 files changed, 5 insertions(+), 5 deletions(-)