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SubjectAntw: [EXT] [PATCH] scsi: Replace zero-length array with flexible-array member
Hi!

Personally I think variable-sized structures are a bad thing, independent of the syntax being used.
30 years ago saving one indirection would have been an argument for such structures, but nowadays?

Regards,
Ulrich

>>> "Gustavo A. R. Silva" <gustavo@embeddedor.com> schrieb am 24.02.2020 um 17:14
in Nachricht
<32123_1582744382_5E56C33B_32123_188_1_20200224161406.GA21454@embeddedor>:
> 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/scsi/fnic/vnic_devcmd.h | 2 +-
> drivers/scsi/ipr.h | 6 +++---
> drivers/scsi/isci/sas.h | 2 +-
> drivers/scsi/mpt3sas/mpt3sas_scsih.c | 2 +-
> drivers/scsi/mvsas/mv_sas.h | 2 +-
> drivers/scsi/mvumi.h | 4 ++--
> drivers/scsi/pmcraid.h | 2 +-
> drivers/scsi/snic/vnic_devcmd.h | 2 +-
> drivers/scsi/stex.c | 2 +-
> include/scsi/iscsi_if.h | 10 +++++-----
> include/scsi/scsi_bsg_iscsi.h | 2 +-
> include/scsi/scsi_device.h | 4 ++--
> include/scsi/scsi_host.h | 2 +-
> include/scsi/scsi_ioctl.h | 2 +-
> include/scsi/srp.h | 8 ++++----
> include/uapi/scsi/scsi_bsg_fc.h | 2 +-
> 16 files changed, 27 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/scsi/fnic/vnic_devcmd.h
> b/drivers/scsi/fnic/vnic_devcmd.h
> index c5dde556dc7c..c20d30e36dfc 100644
> --- a/drivers/scsi/fnic/vnic_devcmd.h
> +++ b/drivers/scsi/fnic/vnic_devcmd.h
> @@ -442,7 +442,7 @@ struct vnic_devcmd_notify {
> struct vnic_devcmd_provinfo {
> u8 oui[3];
> u8 type;
> - u8 data[0];
> + u8 data[];
> };
>
> /*
> diff --git a/drivers/scsi/ipr.h b/drivers/scsi/ipr.h
> index a67baeb36d1f..fd3929a19ab5 100644
> --- a/drivers/scsi/ipr.h
> +++ b/drivers/scsi/ipr.h
> @@ -451,12 +451,12 @@ struct ipr_config_table_hdr64 {
>
> struct ipr_config_table {
> struct ipr_config_table_hdr hdr;
> - struct ipr_config_table_entry dev[0];
> + struct ipr_config_table_entry dev[];
> }__attribute__((packed, aligned (4)));
>
> struct ipr_config_table64 {
> struct ipr_config_table_hdr64 hdr64;
> - struct ipr_config_table_entry64 dev[0];
> + struct ipr_config_table_entry64 dev[];
> }__attribute__((packed, aligned (8)));
>
> struct ipr_config_table_entry_wrapper {
> @@ -792,7 +792,7 @@ struct ipr_mode_page28 {
> struct ipr_mode_page_hdr hdr;
> u8 num_entries;
> u8 entry_length;
> - struct ipr_dev_bus_entry bus[0];
> + struct ipr_dev_bus_entry bus[];
> }__attribute__((packed));
>
> struct ipr_mode_page24 {
> diff --git a/drivers/scsi/isci/sas.h b/drivers/scsi/isci/sas.h
> index dc26b4aea99e..15d8f3631ab7 100644
> --- a/drivers/scsi/isci/sas.h
> +++ b/drivers/scsi/isci/sas.h
> @@ -201,7 +201,7 @@ struct smp_req {
> u8 func; /* byte 1 */
> u8 alloc_resp_len; /* byte 2 */
> u8 req_len; /* byte 3 */
> - u8 req_data[0];
> + u8 req_data[];
> } __packed;
>
> /*
> diff --git a/drivers/scsi/mpt3sas/mpt3sas_scsih.c
> b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
> index c597d544eb39..778d5e6ce385 100644
> --- a/drivers/scsi/mpt3sas/mpt3sas_scsih.c
> +++ b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
> @@ -207,7 +207,7 @@ struct fw_event_work {
> u8 ignore;
> u16 event;
> struct kref refcount;
> - char event_data[0] __aligned(4);
> + char event_data[] __aligned(4);
> };
>
> static void fw_event_work_free(struct kref *r)
> diff --git a/drivers/scsi/mvsas/mv_sas.h b/drivers/scsi/mvsas/mv_sas.h
> index 519edc796691..327fdd5ee962 100644
> --- a/drivers/scsi/mvsas/mv_sas.h
> +++ b/drivers/scsi/mvsas/mv_sas.h
> @@ -394,7 +394,7 @@ struct mvs_info {
> dma_addr_t bulk_buffer_dma1;
> #define TRASH_BUCKET_SIZE 0x20000
> void *dma_pool;
> - struct mvs_slot_info slot_info[0];
> + struct mvs_slot_info slot_info[];
> };
>
> struct mvs_prv_info{
> diff --git a/drivers/scsi/mvumi.h b/drivers/scsi/mvumi.h
> index ec8cc2207536..60d5691fc4ab 100644
> --- a/drivers/scsi/mvumi.h
> +++ b/drivers/scsi/mvumi.h
> @@ -130,7 +130,7 @@ enum {
> struct mvumi_hotplug_event {
> u16 size;
> u8 dummy[2];
> - u8 bitmap[0];
> + u8 bitmap[];
> };
>
> struct mvumi_driver_event {
> @@ -290,7 +290,7 @@ struct mvumi_rsp_frame {
>
> struct mvumi_ob_data {
> struct list_head list;
> - unsigned char data[0];
> + unsigned char data[];
> };
>
> struct version_info {
> diff --git a/drivers/scsi/pmcraid.h b/drivers/scsi/pmcraid.h
> index a4f7eb8f50a3..15c962108075 100644
> --- a/drivers/scsi/pmcraid.h
> +++ b/drivers/scsi/pmcraid.h
> @@ -623,7 +623,7 @@ struct pmcraid_aen_msg {
> u32 hostno;
> u32 length;
> u8 reserved[8];
> - u8 data[0];
> + u8 data[];
> };
>
> /* Controller state event message type */
> diff --git a/drivers/scsi/snic/vnic_devcmd.h
> b/drivers/scsi/snic/vnic_devcmd.h
> index d81b4f0ceaaa..0e0fa38f8d90 100644
> --- a/drivers/scsi/snic/vnic_devcmd.h
> +++ b/drivers/scsi/snic/vnic_devcmd.h
> @@ -208,7 +208,7 @@ struct vnic_devcmd_notify {
> struct vnic_devcmd_provinfo {
> u8 oui[3];
> u8 type;
> - u8 data[0];
> + u8 data[];
> };
>
> /*
> diff --git a/drivers/scsi/stex.c b/drivers/scsi/stex.c
> index 33287b6bdf0e..d4f10c0d813c 100644
> --- a/drivers/scsi/stex.c
> +++ b/drivers/scsi/stex.c
> @@ -236,7 +236,7 @@ struct req_msg {
> u8 data_dir;
> u8 payload_sz; /* payload size in 4-byte, not used */
> u8 cdb[STEX_CDB_LENGTH];
> - u32 variable[0];
> + u32 variable[];
> };
>
> struct status_msg {
> diff --git a/include/scsi/iscsi_if.h b/include/scsi/iscsi_if.h
> index 92b11c7e0b4f..b0e240b10bf9 100644
> --- a/include/scsi/iscsi_if.h
> +++ b/include/scsi/iscsi_if.h
> @@ -311,7 +311,7 @@ enum iscsi_param_type {
> struct iscsi_param_info {
> uint32_t len; /* Actual length of the param value */
> uint16_t param; /* iscsi param */
> - uint8_t value[0]; /* length sized value follows */
> + uint8_t value[]; /* length sized value follows */
> } __packed;
>
> struct iscsi_iface_param_info {
> @@ -320,7 +320,7 @@ struct iscsi_iface_param_info {
> uint16_t param; /* iscsi param value */
> uint8_t iface_type; /* IPv4 or IPv6 */
> uint8_t param_type; /* iscsi_param_type */
> - uint8_t value[0]; /* length sized value follows */
> + uint8_t value[]; /* length sized value follows */
> } __packed;
>
> /*
> @@ -697,7 +697,7 @@ enum iscsi_flashnode_param {
> struct iscsi_flashnode_param_info {
> uint32_t len; /* Actual length of the param */
> uint16_t param; /* iscsi param value */
> - uint8_t value[0]; /* length sized value follows */
> + uint8_t value[]; /* length sized value follows */
> } __packed;
>
> enum iscsi_discovery_parent_type {
> @@ -815,7 +815,7 @@ struct iscsi_stats {
> * up to ISCSI_STATS_CUSTOM_MAX
> */
> uint32_t custom_length;
> - struct iscsi_stats_custom custom[0]
> + struct iscsi_stats_custom custom[]
> __attribute__ ((aligned (sizeof(uint64_t))));
> };
>
> @@ -946,7 +946,7 @@ struct iscsi_offload_host_stats {
> * up to ISCSI_HOST_STATS_CUSTOM_MAX
> */
> uint32_t custom_length;
> - struct iscsi_host_stats_custom custom[0]
> + struct iscsi_host_stats_custom custom[]
> __aligned(sizeof(uint64_t));
> };
>
> diff --git a/include/scsi/scsi_bsg_iscsi.h b/include/scsi/scsi_bsg_iscsi.h
> index fa0c820a1663..6b8128005af8 100644
> --- a/include/scsi/scsi_bsg_iscsi.h
> +++ b/include/scsi/scsi_bsg_iscsi.h
> @@ -52,7 +52,7 @@ struct iscsi_bsg_host_vendor {
> uint64_t vendor_id;
>
> /* start of vendor command area */
> - uint32_t vendor_cmd[0];
> + uint32_t vendor_cmd[];
> };
>
> /* Response:
> diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
> index f8312a3e5b42..4dc158cf09b8 100644
> --- a/include/scsi/scsi_device.h
> +++ b/include/scsi/scsi_device.h
> @@ -231,7 +231,7 @@ struct scsi_device {
> struct mutex state_mutex;
> enum scsi_device_state sdev_state;
> struct task_struct *quiesced_by;
> - unsigned long sdev_data[0];
> + unsigned long sdev_data[];
> } __attribute__((aligned(sizeof(unsigned long))));
>
> #define to_scsi_device(d) \
> @@ -315,7 +315,7 @@ struct scsi_target {
> char scsi_level;
> enum scsi_target_state state;
> void *hostdata; /* available to low-level driver */
> - unsigned long starget_data[0]; /* for the transport */
> + unsigned long starget_data[]; /* for the transport */
> /* starget_data must be the last element!!!! */
> } __attribute__((aligned(sizeof(unsigned long))));
>
> diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
> index 7a97fb8104cf..e6811ea8f984 100644
> --- a/include/scsi/scsi_host.h
> +++ b/include/scsi/scsi_host.h
> @@ -682,7 +682,7 @@ struct Scsi_Host {
> * and also because some compilers (m68k) don't automatically force
> * alignment to a long boundary.
> */
> - unsigned long hostdata[0] /* Used for storage of host specific stuff */
> + unsigned long hostdata[] /* Used for storage of host specific stuff */
> __attribute__ ((aligned (sizeof(unsigned long))));
> };
>
> diff --git a/include/scsi/scsi_ioctl.h b/include/scsi/scsi_ioctl.h
> index 4fe69d863b5d..b465799f4d2d 100644
> --- a/include/scsi/scsi_ioctl.h
> +++ b/include/scsi/scsi_ioctl.h
> @@ -27,7 +27,7 @@ struct scsi_device;
> typedef struct scsi_ioctl_command {
> unsigned int inlen;
> unsigned int outlen;
> - unsigned char data[0];
> + unsigned char data[];
> } Scsi_Ioctl_Command;
>
> typedef struct scsi_idlun {
> diff --git a/include/scsi/srp.h b/include/scsi/srp.h
> index 9220758d5087..177d8026e96f 100644
> --- a/include/scsi/srp.h
> +++ b/include/scsi/srp.h
> @@ -109,7 +109,7 @@ struct srp_direct_buf {
> struct srp_indirect_buf {
> struct srp_direct_buf table_desc;
> __be32 len;
> - struct srp_direct_buf desc_list[0];
> + struct srp_direct_buf desc_list[];
> } __attribute__((packed));
>
> /* Immediate data buffer descriptor as defined in SRP2. */
> @@ -244,7 +244,7 @@ struct srp_cmd {
> u8 reserved4;
> u8 add_cdb_len;
> u8 cdb[16];
> - u8 add_data[0];
> + u8 add_data[];
> };
>
> enum {
> @@ -274,7 +274,7 @@ struct srp_rsp {
> __be32 data_in_res_cnt;
> __be32 sense_data_len;
> __be32 resp_data_len;
> - u8 data[0];
> + u8 data[];
> } __attribute__((packed));
>
> struct srp_cred_req {
> @@ -306,7 +306,7 @@ struct srp_aer_req {
> struct scsi_lun lun;
> __be32 sense_data_len;
> u32 reserved3;
> - u8 sense_data[0];
> + u8 sense_data[];
> } __attribute__((packed));
>
> struct srp_aer_rsp {
> diff --git a/include/uapi/scsi/scsi_bsg_fc.h
> b/include/uapi/scsi/scsi_bsg_fc.h
> index 3ae65e93235c..7f5930801f72 100644
> --- a/include/uapi/scsi/scsi_bsg_fc.h
> +++ b/include/uapi/scsi/scsi_bsg_fc.h
> @@ -209,7 +209,7 @@ struct fc_bsg_host_vendor {
> __u64 vendor_id;
>
> /* start of vendor command area */
> - __u32 vendor_cmd[0];
> + __u32 vendor_cmd[];
> };
>
> /* Response:
> --
> 2.25.0
>
> --
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