| Message ID | 20200218205705.GA29805@embeddedor |
|---|---|
| State | Accepted |
| Delegated to: | David Miller |
| Headers | show |
| Series | [next] mlxsw: Replace zero-length array with flexible-array member | expand |
On Tue, Feb 18, 2020 at 02:57:05PM -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> Thanks, Gustavo. Looks good to me. Ran a few tests with a debug config and nothing exploded. I was just about to submit some patches myself, but they will conflict with this patch, so I will wait :) Reviewed-by: Ido Schimmel <idosch@mellanox.com> Tested-by: Ido Schimmel <idosch@mellanox.com>
On 2/19/20 10:43, Ido Schimmel wrote: > On Tue, Feb 18, 2020 at 02:57:05PM -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> > > Thanks, Gustavo. Looks good to me. Ran a few tests with a debug config > and nothing exploded. > haha great! > I was just about to submit some patches myself, but they will conflict > with this patch, so I will wait :) > :) > Reviewed-by: Ido Schimmel <idosch@mellanox.com> > Tested-by: Ido Schimmel <idosch@mellanox.com> > Thanks! -- Gustavo
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com> Date: Tue, 18 Feb 2020 14:57:05 -0600 > 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> Applied, thanks.
diff --git a/drivers/net/ethernet/mellanox/mlxsw/core.c b/drivers/net/ethernet/mellanox/mlxsw/core.c index e9f791c43f20..0d630096a28c 100644 --- a/drivers/net/ethernet/mellanox/mlxsw/core.c +++ b/drivers/net/ethernet/mellanox/mlxsw/core.c @@ -82,7 +82,7 @@ struct mlxsw_core { struct mlxsw_core_port *ports; unsigned int max_ports; bool fw_flash_in_progress; - unsigned long driver_priv[0]; + unsigned long driver_priv[]; /* driver_priv has to be always the last item */ }; diff --git a/drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_keys.c b/drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_keys.c index feb4672a5ac0..bd2207f60722 100644 --- a/drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_keys.c +++ b/drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_keys.c @@ -72,7 +72,7 @@ struct mlxsw_afk_key_info { * is index inside "blocks" */ struct mlxsw_afk_element_usage elusage; - const struct mlxsw_afk_block *blocks[0]; + const struct mlxsw_afk_block *blocks[]; }; static bool diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum1_kvdl.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum1_kvdl.c index 09ee0a807747..a9fff8adc75e 100644 --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum1_kvdl.c +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum1_kvdl.c @@ -60,7 +60,7 @@ static const struct mlxsw_sp1_kvdl_part_info mlxsw_sp1_kvdl_parts_info[] = { struct mlxsw_sp1_kvdl_part { struct mlxsw_sp1_kvdl_part_info info; - unsigned long usage[0]; /* Entries */ + unsigned long usage[]; /* Entries */ }; struct mlxsw_sp1_kvdl { diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum2_kvdl.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum2_kvdl.c index 8d14770766b4..3a73d654017f 100644 --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum2_kvdl.c +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum2_kvdl.c @@ -45,7 +45,7 @@ struct mlxsw_sp2_kvdl_part { unsigned int usage_bit_count; unsigned int indexes_per_usage_bit; unsigned int last_allocated_bit; - unsigned long usage[0]; /* Usage bits */ + unsigned long usage[]; /* Usage bits */ }; struct mlxsw_sp2_kvdl { diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl.c index 3d3cca596116..9368b93dab38 100644 --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl.c +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl.c @@ -58,7 +58,7 @@ struct mlxsw_sp_acl_ruleset { struct mlxsw_sp_acl_ruleset_ht_key ht_key; struct rhashtable rule_ht; unsigned int ref_count; - unsigned long priv[0]; + unsigned long priv[]; /* priv has to be always the last item */ }; @@ -71,7 +71,7 @@ struct mlxsw_sp_acl_rule { u64 last_used; u64 last_packets; u64 last_bytes; - unsigned long priv[0]; + unsigned long priv[]; /* priv has to be always the last item */ }; diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_bloom_filter.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_bloom_filter.c index 3a2de13fcb68..dbd3bebf11ec 100644 --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_bloom_filter.c +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_bloom_filter.c @@ -13,7 +13,7 @@ struct mlxsw_sp_acl_bf { struct mutex lock; /* Protects Bloom Filter updates. */ unsigned int bank_size; - refcount_t refcnt[0]; + refcount_t refcnt[]; }; /* Bloom filter uses a crc-16 hash over chunks of data which contain 4 key diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.c index e993159e8e4c..430da69003d8 100644 --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.c +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.c @@ -224,7 +224,7 @@ struct mlxsw_sp_acl_tcam_vchunk; struct mlxsw_sp_acl_tcam_chunk { struct mlxsw_sp_acl_tcam_vchunk *vchunk; struct mlxsw_sp_acl_tcam_region *region; - unsigned long priv[0]; + unsigned long priv[]; /* priv has to be always the last item */ }; @@ -243,7 +243,7 @@ struct mlxsw_sp_acl_tcam_vchunk { struct mlxsw_sp_acl_tcam_entry { struct mlxsw_sp_acl_tcam_ventry *ventry; struct mlxsw_sp_acl_tcam_chunk *chunk; - unsigned long priv[0]; + unsigned long priv[]; /* priv has to be always the last item */ }; diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.h b/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.h index 5965913565a5..96437992b102 100644 --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.h +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.h @@ -20,7 +20,7 @@ struct mlxsw_sp_acl_tcam { struct mutex lock; /* guards vregion list */ struct list_head vregion_list; u32 vregion_rehash_intrvl; /* ms */ - unsigned long priv[0]; + unsigned long priv[]; /* priv has to be always the last item */ }; @@ -86,7 +86,7 @@ struct mlxsw_sp_acl_tcam_region { char tcam_region_info[MLXSW_REG_PXXX_TCAM_REGION_INFO_LEN]; struct mlxsw_afk_key_info *key_info; struct mlxsw_sp *mlxsw_sp; - unsigned long priv[0]; + unsigned long priv[]; /* priv has to be always the last item */ }; diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_kvdl.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_kvdl.c index 1e4cdee7bcd7..715ec8ecacba 100644 --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_kvdl.c +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_kvdl.c @@ -8,7 +8,7 @@ struct mlxsw_sp_kvdl { const struct mlxsw_sp_kvdl_ops *kvdl_ops; - unsigned long priv[0]; + unsigned long priv[]; /* priv has to be always the last item */ }; diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_mr.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_mr.c index 54275624718b..423eedebcd22 100644 --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_mr.c +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_mr.c @@ -68,7 +68,7 @@ struct mlxsw_sp_mr_table { struct list_head route_list; struct rhashtable route_ht; const struct mlxsw_sp_mr_table_ops *ops; - char catchall_route_priv[0]; + char catchall_route_priv[]; /* catchall_route_priv has to be always the last item */ }; diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_nve.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_nve.c index 2153bcc4b585..16a130c2f21c 100644 --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_nve.c +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_nve.c @@ -67,7 +67,7 @@ struct mlxsw_sp_nve_mc_record { struct mlxsw_sp_nve_mc_list *mc_list; const struct mlxsw_sp_nve_mc_record_ops *ops; u32 kvdl_index; - struct mlxsw_sp_nve_mc_entry entries[0]; + struct mlxsw_sp_nve_mc_entry entries[]; }; struct mlxsw_sp_nve_mc_list {
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/mlxsw/core.c | 2 +- drivers/net/ethernet/mellanox/mlxsw/core_acl_flex_keys.c | 2 +- drivers/net/ethernet/mellanox/mlxsw/spectrum1_kvdl.c | 2 +- drivers/net/ethernet/mellanox/mlxsw/spectrum2_kvdl.c | 2 +- drivers/net/ethernet/mellanox/mlxsw/spectrum_acl.c | 4 ++-- .../net/ethernet/mellanox/mlxsw/spectrum_acl_bloom_filter.c | 2 +- drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.c | 4 ++-- drivers/net/ethernet/mellanox/mlxsw/spectrum_acl_tcam.h | 4 ++-- drivers/net/ethernet/mellanox/mlxsw/spectrum_kvdl.c | 2 +- drivers/net/ethernet/mellanox/mlxsw/spectrum_mr.c | 2 +- drivers/net/ethernet/mellanox/mlxsw/spectrum_nve.c | 2 +- 11 files changed, 14 insertions(+), 14 deletions(-)