[Devel] [PATCH VZ10] fs/fuse kio: replace zero-length array with flexible array syntax

[Alexey Kuznetsov]

Ack. If it compiles it must be all right.

On Wed, May 6, 2026 at 6:41 PM Liu Kui <kui.liu at virtuozzo.com> wrote:
>
> With FORTIFY_SOURCE, memcpy to a zero-length arrary field is flagged
> as field-spanning, causing kernel warning. Switch to the C99 flexible
> array [] syntax to fix this.
>
> Changes:
>  - _data_buf[0] -> _data_buf[] in struct krpc_completion
>  - sync_resp[0] -> sync_resp[] in struct pcs_cs_iohdr
>  - nodes[0] -> nodes[] in struct pcs_cs_map_prop
>  - cs[0] -> cs[] in struct pcs_cs_list
>  - cs[0] -> cs[] in struct pcs_ioc_getmap
>
> Link: https://virtuozzo.atlassian.net/browse/VSTOR-130548
>
> Signed-off-by: Liu Kui <kui.liu at virtuozzo.com>
> ---
>  fs/fuse/kio/pcs/pcs_cs_prot.h | 4 ++--
>  fs/fuse/kio/pcs/pcs_ioctl.h   | 2 +-
>  fs/fuse/kio/pcs/pcs_krpc.h    | 2 +-
>  fs/fuse/kio/pcs/pcs_map.h     | 2 +-
>  4 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/fs/fuse/kio/pcs/pcs_cs_prot.h b/fs/fuse/kio/pcs/pcs_cs_prot.h
> index c72066de7be4..c524d28b551e 100644
> --- a/fs/fuse/kio/pcs/pcs_cs_prot.h
> +++ b/fs/fuse/kio/pcs/pcs_cs_prot.h
> @@ -79,7 +79,7 @@ struct pcs_cs_iohdr {
>                 u32                     fiemap_count;   /* Used only in FIEMAP request, limit on number of extents to return */
>         };
>         struct pcs_cs_sync_data sync;           /* Filled in all requests and responses */
> -       struct pcs_cs_sync_resp sync_resp[0];   /* Used only in response to write/sync */
> +       struct pcs_cs_sync_resp sync_resp[];    /* Used only in response to write/sync */
>  } __attribute__((aligned(8)));
>
>  static inline int pcs_cs_use_aligned_io(u32 storage_version)
> @@ -171,7 +171,7 @@ struct pcs_cs_map_prop {
>         u16                     chain_nodes;
>         u16                     reserved;
>         u32                     nnodes;
> -       struct pcs_cs_node_desc nodes[0];
> +       struct pcs_cs_node_desc nodes[];
>  } __attribute__((aligned(8)));
>
>  #define CS_OBJ_UNKNOWN         -1
> diff --git a/fs/fuse/kio/pcs/pcs_ioctl.h b/fs/fuse/kio/pcs/pcs_ioctl.h
> index fb22cf8a01b0..07a87d6507f3 100644
> --- a/fs/fuse/kio/pcs/pcs_ioctl.h
> +++ b/fs/fuse/kio/pcs/pcs_ioctl.h
> @@ -74,7 +74,7 @@ struct pcs_ioc_getmap
>         /* TODO: cs array is only for OUT ? */
>         u32                     cs_cnt;         /* The number of CS (including root) entries that follows */
>         u32                     cs_max;         /* Max number of CS (including root) entries requested */
> -       struct pcs_cs_info      cs[0];          /* Array of CS including root */
> +       struct pcs_cs_info      cs[];           /* Array of CS including root */
>  };
>
>  #define PCS_IOC_NOCSUMONREAD   _IOW('V',3,u32)
> diff --git a/fs/fuse/kio/pcs/pcs_krpc.h b/fs/fuse/kio/pcs/pcs_krpc.h
> index 6a090ef66185..d5a7a56d84c8 100644
> --- a/fs/fuse/kio/pcs/pcs_krpc.h
> +++ b/fs/fuse/kio/pcs/pcs_krpc.h
> @@ -99,7 +99,7 @@ struct krpc_completion {
>
>         void            *private;
>         int                     data_len;
> -       u8                      _data_buf[0];
> +       u8                      _data_buf[];
>  };
>
>  #define KRPC_MAX_DATA_PAGES                    256
> diff --git a/fs/fuse/kio/pcs/pcs_map.h b/fs/fuse/kio/pcs/pcs_map.h
> index bf8a0e7177d0..788a8cb16d8e 100644
> --- a/fs/fuse/kio/pcs/pcs_map.h
> +++ b/fs/fuse/kio/pcs/pcs_map.h
> @@ -127,7 +127,7 @@ struct pcs_cs_list
>         int                     write_timeout;
>         int                     nsrv;
>         PCS_MAP_VERSION_T       version;                /* version inherented from map */
> -       struct pcs_cs_record    cs[0];
> +       struct pcs_cs_record    cs[];
>  };
>
>  /* TODO, LOCKING!!!!!
> --
> 2.39.5 (Apple Git-154)