Subject: Re: [PATCH V2] include: linux: Regularise the use of FIELD_SIZEOF macro

From: Kees Cook <[email-masked]>
Date: Tue, 11 Jun 2019 13:46:34 -0700

On Wed, Jun 12, 2019 at 01:08:36AM +0530, Shyam Saini wrote:
> In favour of FIELD_SIZEOF, this patch also deprecates other two similar
> macros sizeof_field and SIZEOF_FIELD.
> 
> For code compatibility reason, retain sizeof_field macro as a wrapper macro
> to FIELD_SIZEOF

Can you explain this part? First sentence says you want to remove
sizeof_field, and the second says you're keeping it? I thought the point
was to switch all of these to FIELD_SIZEOF()?

-Kees

> 
> Signed-off-by: Shyam Saini <[email-masked]>
> ---
> Changelog:
> 
> V1->V2
> - Consolidate previous patch 1 and 2 into single patch
> - For code compatibility reason, retain sizeof_field macro as a
>   wrapper macro to FIELD_SIZEOF
>  
>  arch/arm64/include/asm/processor.h                 | 10 +++++-----
>  arch/mips/cavium-octeon/executive/cvmx-bootmem.c   |  9 +--------
>  drivers/gpu/drm/i915/gvt/scheduler.c               |  2 +-
>  drivers/net/ethernet/mellanox/mlxsw/spectrum_fid.c |  4 ++--
>  fs/befs/linuxvfs.c                                 |  2 +-
>  fs/ext2/super.c                                    |  2 +-
>  fs/ext4/super.c                                    |  2 +-
>  fs/freevxfs/vxfs_super.c                           |  2 +-
>  fs/orangefs/super.c                                |  2 +-
>  fs/ufs/super.c                                     |  2 +-
>  include/linux/kernel.h                             |  9 ---------
>  include/linux/slab.h                               |  2 +-
>  include/linux/stddef.h                             | 17 ++++++++++++++---
>  kernel/fork.c                                      |  2 +-
>  kernel/utsname.c                                   |  2 +-
>  net/caif/caif_socket.c                             |  2 +-
>  net/core/skbuff.c                                  |  2 +-
>  net/ipv4/raw.c                                     |  2 +-
>  net/ipv6/raw.c                                     |  2 +-
>  net/sctp/socket.c                                  |  4 ++--
>  tools/testing/selftests/bpf/bpf_util.h             | 22 +++++++++++++++++++---
>  virt/kvm/kvm_main.c                                |  2 +-
>  22 files changed, 58 insertions(+), 47 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
> index fcd0e691b1ea..ace906d887cc 100644
> --- a/arch/arm64/include/asm/processor.h
> +++ b/arch/arm64/include/asm/processor.h
> @@ -164,13 +164,13 @@ static inline void arch_thread_struct_whitelist(unsigned long *offset,
>  						unsigned long *size)
>  {
>  	/* Verify that there is no padding among the whitelisted fields: */
> -	BUILD_BUG_ON(sizeof_field(struct thread_struct, uw) !=
> -		     sizeof_field(struct thread_struct, uw.tp_value) +
> -		     sizeof_field(struct thread_struct, uw.tp2_value) +
> -		     sizeof_field(struct thread_struct, uw.fpsimd_state));
> +	BUILD_BUG_ON(FIELD_SIZEOF(struct thread_struct, uw) !=
> +		     FIELD_SIZEOF(struct thread_struct, uw.tp_value) +
> +		     FIELD_SIZEOF(struct thread_struct, uw.tp2_value) +
> +		     FIELD_SIZEOF(struct thread_struct, uw.fpsimd_state));
>  
>  	*offset = offsetof(struct thread_struct, uw);
> -	*size = sizeof_field(struct thread_struct, uw);
> +	*size = FIELD_SIZEOF(struct thread_struct, uw);
>  }
>  
>  #ifdef CONFIG_COMPAT
> diff --git a/arch/mips/cavium-octeon/executive/cvmx-bootmem.c b/arch/mips/cavium-octeon/executive/cvmx-bootmem.c
> index ba8f82a29a81..44b506a14666 100644
> --- a/arch/mips/cavium-octeon/executive/cvmx-bootmem.c
> +++ b/arch/mips/cavium-octeon/executive/cvmx-bootmem.c
> @@ -45,13 +45,6 @@ static struct cvmx_bootmem_desc *cvmx_bootmem_desc;
>  /* See header file for descriptions of functions */
>  
>  /**
> - * This macro returns the size of a member of a structure.
> - * Logically it is the same as "sizeof(s::field)" in C++, but
> - * C lacks the "::" operator.
> - */
> -#define SIZEOF_FIELD(s, field) sizeof(((s *)NULL)->field)
> -
> -/**
>   * This macro returns a member of the
>   * cvmx_bootmem_named_block_desc_t structure. These members can't
>   * be directly addressed as they might be in memory not directly
> @@ -65,7 +58,7 @@ static struct cvmx_bootmem_desc *cvmx_bootmem_desc;
>  #define CVMX_BOOTMEM_NAMED_GET_FIELD(addr, field)			\
>  	__cvmx_bootmem_desc_get(addr,					\
>  		offsetof(struct cvmx_bootmem_named_block_desc, field),	\
> -		SIZEOF_FIELD(struct cvmx_bootmem_named_block_desc, field))
> +		FIELD_SIZEOF(struct cvmx_bootmem_named_block_desc, field))
>  
>  /**
>   * This function is the implementation of the get macros defined
> diff --git a/drivers/gpu/drm/i915/gvt/scheduler.c b/drivers/gpu/drm/i915/gvt/scheduler.c
> index 0f919f0a43d4..820f95a52542 100644
> --- a/drivers/gpu/drm/i915/gvt/scheduler.c
> +++ b/drivers/gpu/drm/i915/gvt/scheduler.c
> @@ -1243,7 +1243,7 @@ int intel_vgpu_setup_submission(struct intel_vgpu *vgpu)
>  						  sizeof(struct intel_vgpu_workload), 0,
>  						  SLAB_HWCACHE_ALIGN,
>  						  offsetof(struct intel_vgpu_workload, rb_tail),
> -						  sizeof_field(struct intel_vgpu_workload, rb_tail),
> +						  FIELD_SIZEOF(struct intel_vgpu_workload, rb_tail),
>  						  NULL);
>  
>  	if (!s->workloads) {
> diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_fid.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_fid.c
> index 46baf3b44309..c0447bf07fbb 100644
> --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_fid.c
> +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_fid.c
> @@ -49,13 +49,13 @@ struct mlxsw_sp_fid_8021d {
>  };
>  
>  static const struct rhashtable_params mlxsw_sp_fid_ht_params = {
> -	.key_len = sizeof_field(struct mlxsw_sp_fid, fid_index),
> +	.key_len = FIELD_SIZEOF(struct mlxsw_sp_fid, fid_index),
>  	.key_offset = offsetof(struct mlxsw_sp_fid, fid_index),
>  	.head_offset = offsetof(struct mlxsw_sp_fid, ht_node),
>  };
>  
>  static const struct rhashtable_params mlxsw_sp_fid_vni_ht_params = {
> -	.key_len = sizeof_field(struct mlxsw_sp_fid, vni),
> +	.key_len = FIELD_SIZEOF(struct mlxsw_sp_fid, vni),
>  	.key_offset = offsetof(struct mlxsw_sp_fid, vni),
>  	.head_offset = offsetof(struct mlxsw_sp_fid, vni_ht_node),
>  };
> diff --git a/fs/befs/linuxvfs.c b/fs/befs/linuxvfs.c
> index 462d096ff3e9..06ffd4829e2e 100644
> --- a/fs/befs/linuxvfs.c
> +++ b/fs/befs/linuxvfs.c
> @@ -438,7 +438,7 @@ befs_init_inodecache(void)
>  					SLAB_ACCOUNT),
>  				offsetof(struct befs_inode_info,
>  					i_data.symlink),
> -				sizeof_field(struct befs_inode_info,
> +				FIELD_SIZEOF(struct befs_inode_info,
>  					i_data.symlink),
>  				init_once);
>  	if (befs_inode_cachep == NULL)
> diff --git a/fs/ext2/super.c b/fs/ext2/super.c
> index 1d7ab73b1014..d9a6c81f4a47 100644
> --- a/fs/ext2/super.c
> +++ b/fs/ext2/super.c
> @@ -220,7 +220,7 @@ static int __init init_inodecache(void)
>  				(SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD|
>  					SLAB_ACCOUNT),
>  				offsetof(struct ext2_inode_info, i_data),
> -				sizeof_field(struct ext2_inode_info, i_data),
> +				FIELD_SIZEOF(struct ext2_inode_info, i_data),
>  				init_once);
>  	if (ext2_inode_cachep == NULL)
>  		return -ENOMEM;
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 4079605d437a..b1b5856248bd 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1148,7 +1148,7 @@ static int __init init_inodecache(void)
>  				(SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD|
>  					SLAB_ACCOUNT),
>  				offsetof(struct ext4_inode_info, i_data),
> -				sizeof_field(struct ext4_inode_info, i_data),
> +				FIELD_SIZEOF(struct ext4_inode_info, i_data),
>  				init_once);
>  	if (ext4_inode_cachep == NULL)
>  		return -ENOMEM;
> diff --git a/fs/freevxfs/vxfs_super.c b/fs/freevxfs/vxfs_super.c
> index a89f68c3cbed..ffd22f85bbe0 100644
> --- a/fs/freevxfs/vxfs_super.c
> +++ b/fs/freevxfs/vxfs_super.c
> @@ -329,7 +329,7 @@ vxfs_init(void)
>  			sizeof(struct vxfs_inode_info), 0,
>  			SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD,
>  			offsetof(struct vxfs_inode_info, vii_immed.vi_immed),
> -			sizeof_field(struct vxfs_inode_info,
> +			FIELD_SIZEOF(struct vxfs_inode_info,
>  				vii_immed.vi_immed),
>  			NULL);
>  	if (!vxfs_inode_cachep)
> diff --git a/fs/orangefs/super.c b/fs/orangefs/super.c
> index ee5efdc35cc1..30f625059ad9 100644
> --- a/fs/orangefs/super.c
> +++ b/fs/orangefs/super.c
> @@ -646,7 +646,7 @@ int orangefs_inode_cache_initialize(void)
>  					ORANGEFS_CACHE_CREATE_FLAGS,
>  					offsetof(struct orangefs_inode_s,
>  						link_target),
> -					sizeof_field(struct orangefs_inode_s,
> +					FIELD_SIZEOF(struct orangefs_inode_s,
>  						link_target),
>  					orangefs_inode_cache_ctor);
>  
> diff --git a/fs/ufs/super.c b/fs/ufs/super.c
> index 3d247c0d92aa..1e8bcd950f6d 100644
> --- a/fs/ufs/super.c
> +++ b/fs/ufs/super.c
> @@ -1469,7 +1469,7 @@ static int __init init_inodecache(void)
>  				(SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD|
>  					SLAB_ACCOUNT),
>  				offsetof(struct ufs_inode_info, i_u1.i_symlink),
> -				sizeof_field(struct ufs_inode_info,
> +				FIELD_SIZEOF(struct ufs_inode_info,
>  					i_u1.i_symlink),
>  				init_once);
>  	if (ufs_inode_cachep == NULL)
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index 74b1ee9027f5..4672391cdb5b 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -79,15 +79,6 @@
>   */
>  #define round_down(x, y) ((x) & ~__round_mask(x, y))
>  
> -/**
> - * FIELD_SIZEOF - get the size of a struct's field
> - * @t: the target struct
> - * @f: the target struct's field
> - * Return: the size of @f in the struct definition without having a
> - * declared instance of @t.
> - */
> -#define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f))
> -
>  #define DIV_ROUND_UP __KERNEL_DIV_ROUND_UP
>  
>  #define DIV_ROUND_DOWN_ULL(ll, d) \
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index 9449b19c5f10..8bdfdd389b37 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -175,7 +175,7 @@ void memcg_destroy_kmem_caches(struct mem_cgroup *);
>  			sizeof(struct __struct),			\
>  			__alignof__(struct __struct), (__flags),	\
>  			offsetof(struct __struct, __field),		\
> -			sizeof_field(struct __struct, __field), NULL)
> +			FIELD_SIZEOF(struct __struct, __field), NULL)
>  
>  /*
>   * Common kmalloc functions provided by all allocators
> diff --git a/include/linux/stddef.h b/include/linux/stddef.h
> index 998a4ba28eba..a5960e2b4a8b 100644
> --- a/include/linux/stddef.h
> +++ b/include/linux/stddef.h
> @@ -20,12 +20,23 @@ enum {
>  #endif
>  
>  /**
> - * sizeof_field(TYPE, MEMBER)
> + * FIELD_SIZEOF - get the size of a struct's field
> + * @t: the target struct
> + * @f: the target struct's field
> + * Return: the size of @f in the struct definition without having a
> + * declared instance of @t.
> + */
> +#define FIELD_SIZEOF(t, f) (sizeof(((t *)0)->f))
> +
> +/*
> + * For code compatibility
>   *
> + * sizeof_field(TYPE, MEMBER)
>   * @TYPE: The structure containing the field of interest
>   * @MEMBER: The field to return the size of
>   */
> -#define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
> +
> +#define sizeof_field(TYPE, MEMBER) FIELD_SIZEOF(TYPE, MEMBER)
>  
>  /**
>   * offsetofend(TYPE, MEMBER)
> @@ -34,6 +45,6 @@ enum {
>   * @MEMBER: The member within the structure to get the end offset of
>   */
>  #define offsetofend(TYPE, MEMBER) \
> -	(offsetof(TYPE, MEMBER)	+ sizeof_field(TYPE, MEMBER))
> +	(offsetof(TYPE, MEMBER)	+ FIELD_SIZEOF(TYPE, MEMBER))
>  
>  #endif
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 75675b9bf6df..ef40b95bf82c 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -2553,7 +2553,7 @@ void __init proc_caches_init(void)
>  			mm_size, ARCH_MIN_MMSTRUCT_ALIGN,
>  			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
>  			offsetof(struct mm_struct, saved_auxv),
> -			sizeof_field(struct mm_struct, saved_auxv),
> +			FIELD_SIZEOF(struct mm_struct, saved_auxv),
>  			NULL);
>  	vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);
>  	mmap_init();
> diff --git a/kernel/utsname.c b/kernel/utsname.c
> index f0e491193009..28257c571553 100644
> --- a/kernel/utsname.c
> +++ b/kernel/utsname.c
> @@ -174,6 +174,6 @@ void __init uts_ns_init(void)
>  			"uts_namespace", sizeof(struct uts_namespace), 0,
>  			SLAB_PANIC|SLAB_ACCOUNT,
>  			offsetof(struct uts_namespace, name),
> -			sizeof_field(struct uts_namespace, name),
> +			FIELD_SIZEOF(struct uts_namespace, name),
>  			NULL);
>  }
> diff --git a/net/caif/caif_socket.c b/net/caif/caif_socket.c
> index 13ea920600ae..3306bbed77eb 100644
> --- a/net/caif/caif_socket.c
> +++ b/net/caif/caif_socket.c
> @@ -1033,7 +1033,7 @@ static int caif_create(struct net *net, struct socket *sock, int protocol,
>  		.owner = THIS_MODULE,
>  		.obj_size = sizeof(struct caifsock),
>  		.useroffset = offsetof(struct caifsock, conn_req.param),
> -		.usersize = sizeof_field(struct caifsock, conn_req.param)
> +		.usersize = FIELD_SIZEOF(struct caifsock, conn_req.param)
>  	};
>  
>  	if (!capable(CAP_SYS_ADMIN) && !capable(CAP_NET_ADMIN))
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 47c1aa9ee045..816bea0c4a8e 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -3983,7 +3983,7 @@ void __init skb_init(void)
>  					      0,
>  					      SLAB_HWCACHE_ALIGN|SLAB_PANIC,
>  					      offsetof(struct sk_buff, cb),
> -					      sizeof_field(struct sk_buff, cb),
> +					      FIELD_SIZEOF(struct sk_buff, cb),
>  					      NULL);
>  	skbuff_fclone_cache = kmem_cache_create("skbuff_fclone_cache",
>  						sizeof(struct sk_buff_fclones),
> diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
> index 0b8e06ca75d6..efa4c745f7b9 100644
> --- a/net/ipv4/raw.c
> +++ b/net/ipv4/raw.c
> @@ -977,7 +977,7 @@ struct proto raw_prot = {
>  	.unhash		   = raw_unhash_sk,
>  	.obj_size	   = sizeof(struct raw_sock),
>  	.useroffset	   = offsetof(struct raw_sock, filter),
> -	.usersize	   = sizeof_field(struct raw_sock, filter),
> +	.usersize	   = FIELD_SIZEOF(struct raw_sock, filter),
>  	.h.raw_hash	   = &raw_v4_hashinfo,
>  #ifdef CONFIG_COMPAT
>  	.compat_setsockopt = compat_raw_setsockopt,
> diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
> index 70693bc7ad9d..257c71e22d74 100644
> --- a/net/ipv6/raw.c
> +++ b/net/ipv6/raw.c
> @@ -1292,7 +1292,7 @@ struct proto rawv6_prot = {
>  	.unhash		   = raw_unhash_sk,
>  	.obj_size	   = sizeof(struct raw6_sock),
>  	.useroffset	   = offsetof(struct raw6_sock, filter),
> -	.usersize	   = sizeof_field(struct raw6_sock, filter),
> +	.usersize	   = FIELD_SIZEOF(struct raw6_sock, filter),
>  	.h.raw_hash	   = &raw_v6_hashinfo,
>  #ifdef CONFIG_COMPAT
>  	.compat_setsockopt = compat_rawv6_setsockopt,
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index 39ea0a37af09..6b648a6033b9 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -9377,7 +9377,7 @@ struct proto sctp_prot = {
>  	.useroffset  =  offsetof(struct sctp_sock, subscribe),
>  	.usersize    =  offsetof(struct sctp_sock, initmsg) -
>  				offsetof(struct sctp_sock, subscribe) +
> -				sizeof_field(struct sctp_sock, initmsg),
> +				FIELD_SIZEOF(struct sctp_sock, initmsg),
>  	.sysctl_mem  =  sysctl_sctp_mem,
>  	.sysctl_rmem =  sysctl_sctp_rmem,
>  	.sysctl_wmem =  sysctl_sctp_wmem,
> @@ -9419,7 +9419,7 @@ struct proto sctpv6_prot = {
>  	.useroffset	= offsetof(struct sctp6_sock, sctp.subscribe),
>  	.usersize	= offsetof(struct sctp6_sock, sctp.initmsg) -
>  				offsetof(struct sctp6_sock, sctp.subscribe) +
> -				sizeof_field(struct sctp6_sock, sctp.initmsg),
> +				FIELD_SIZEOF(struct sctp6_sock, sctp.initmsg),
>  	.sysctl_mem	= sysctl_sctp_mem,
>  	.sysctl_rmem	= sysctl_sctp_rmem,
>  	.sysctl_wmem	= sysctl_sctp_wmem,
> diff --git a/tools/testing/selftests/bpf/bpf_util.h b/tools/testing/selftests/bpf/bpf_util.h
> index a29206ebbd13..571c35aac90f 100644
> --- a/tools/testing/selftests/bpf/bpf_util.h
> +++ b/tools/testing/selftests/bpf/bpf_util.h
> @@ -58,13 +58,29 @@ static inline unsigned int bpf_num_possible_cpus(void)
>  # define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
>  #endif
>  
> -#ifndef sizeof_field
> -#define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
> +/*
> + * FIELD_SIZEOF - get the size of a struct's field
> + * @t: the target struct
> + * @f: the target struct's field
> + * Return: the size of @f in the struct definition without having a
> + * declared instance of @t.
> + */
> +#ifndef FIELD_SIZEOF
> +#define FIELD_SIZEOF(t, f) (sizeof(((t *)0)->f))
>  #endif
>  
> +/*
> + * For code compatibility
> + *
> + * sizeof_field(TYPE, MEMBER)
> + * @TYPE: The structure containing the field of interest
> + * @MEMBER: The field to return the size of
> + */
> +#define sizeof_field(TYPE, MEMBER) FIELD_SIZEOF(TYPE, MEMBER)
> +
>  #ifndef offsetofend
>  #define offsetofend(TYPE, MEMBER) \
> -	(offsetof(TYPE, MEMBER)	+ sizeof_field(TYPE, MEMBER))
> +	(offsetof(TYPE, MEMBER)	+ FIELD_SIZEOF(TYPE, MEMBER))
>  #endif
>  
>  #endif /* __BPF_UTIL__ */
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index ca54b09adf5b..e43e3a26f6ab 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -4275,7 +4275,7 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
>  		kmem_cache_create_usercopy("kvm_vcpu", vcpu_size, vcpu_align,
>  					   SLAB_ACCOUNT,
>  					   offsetof(struct kvm_vcpu, arch),
> -					   sizeof_field(struct kvm_vcpu, arch),
> +					   FIELD_SIZEOF(struct kvm_vcpu, arch),
>  					   NULL);
>  	if (!kvm_vcpu_cache) {
>  		r = -ENOMEM;
> -- 
> 2.11.0
> 

-- 
Kees Cook