Subject: Re: [PATCH bpf-next v2 1/8] bpf: implement getsockopt and setsockopt hooks

From: Stanislav Fomichev <[email-masked]>
Date: Fri, 7 Jun 2019 08:55:21 -0700

On 06/07, Martin Lau wrote:
> On Thu, Jun 06, 2019 at 10:51:39AM -0700, Stanislav Fomichev wrote:
> > Implement new BPF_PROG_TYPE_CGROUP_SOCKOPT program type and
> > BPF_CGROUP_{G,S}ETSOCKOPT cgroup hooks.
> > 
> > BPF_CGROUP_SETSOCKOPT get a read-only view of the setsockopt arguments.
> > BPF_CGROUP_GETSOCKOPT can modify the supplied buffer.
> > Both of them reuse existing PTR_TO_PACKET{,_END} infrastructure.
> > 
> > The buffer memory is pre-allocated (because I don't think there is
> > a precedent for working with __user memory from bpf). This might be
> > slow to do for each {s,g}etsockopt call, that's why I've added
> > __cgroup_bpf_prog_array_is_empty that exits early if there is nothing
> > attached to a cgroup. Note, however, that there is a race between
> > __cgroup_bpf_prog_array_is_empty and BPF_PROG_RUN_ARRAY where cgroup
> > program layout might have changed; this should not be a problem
> > because in general there is a race between multiple calls to
> > {s,g}etsocktop and user adding/removing bpf progs from a cgroup.
> > 
> > The return code of the BPF program is handled as follows:
> > * 0: EPERM
> > * 1: success, execute kernel {s,g}etsockopt path after BPF prog exits
> > * 2: success, do _not_ execute kernel {s,g}etsockopt path after BPF
> >      prog exits
> > 
> > v2:
> > * moved bpf_sockopt_kern fields around to remove a hole (Martin Lau)
> > * aligned bpf_sockopt_kern->buf to 8 bytes (Martin Lau)
> > * bpf_prog_array_is_empty instead of bpf_prog_array_length (Martin Lau)
> > * added [0,2] return code check to verifier (Martin Lau)
> > * dropped unused buf[64] from the stack (Martin Lau)
> > * use PTR_TO_SOCKET for bpf_sockopt->sk (Martin Lau)
> > * dropped bpf_target_off from ctx rewrites (Martin Lau)
> > * use return code for kernel bypass (Martin Lau & Andrii Nakryiko)
> > 
> > Signed-off-by: Stanislav Fomichev <[email-masked]>
> > ---
> >  include/linux/bpf-cgroup.h |  29 ++++
> >  include/linux/bpf.h        |  46 ++++++
> >  include/linux/bpf_types.h  |   1 +
> >  include/linux/filter.h     |  13 ++
> >  include/uapi/linux/bpf.h   |  14 ++
> >  kernel/bpf/cgroup.c        | 277 +++++++++++++++++++++++++++++++++++++
> >  kernel/bpf/core.c          |   9 ++
> >  kernel/bpf/syscall.c       |  19 +++
> >  kernel/bpf/verifier.c      |  15 ++
> >  net/core/filter.c          |   4 +-
> >  net/socket.c               |  18 +++
> >  11 files changed, 443 insertions(+), 2 deletions(-)
> > 
> > diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
> > index b631ee75762d..406f1ba82531 100644
> > --- a/include/linux/bpf-cgroup.h
> > +++ b/include/linux/bpf-cgroup.h
> > @@ -124,6 +124,13 @@ int __cgroup_bpf_run_filter_sysctl(struct ctl_table_header *head,
> >  				   loff_t *ppos, void **new_buf,
> >  				   enum bpf_attach_type type);
> >  
> > +int __cgroup_bpf_run_filter_setsockopt(struct sock *sock, int level,
> > +				       int optname, char __user *optval,
> > +				       unsigned int optlen);
> > +int __cgroup_bpf_run_filter_getsockopt(struct sock *sock, int level,
> > +				       int optname, char __user *optval,
> > +				       int __user *optlen);
> > +
> >  static inline enum bpf_cgroup_storage_type cgroup_storage_type(
> >  	struct bpf_map *map)
> >  {
> > @@ -280,6 +287,26 @@ int bpf_percpu_cgroup_storage_update(struct bpf_map *map, void *key,
> >  	__ret;								       \
> >  })
> >  
> > +#define BPF_CGROUP_RUN_PROG_SETSOCKOPT(sock, level, optname, optval, optlen)   \
> > +({									       \
> > +	int __ret = 0;							       \
> > +	if (cgroup_bpf_enabled)						       \
> > +		__ret = __cgroup_bpf_run_filter_setsockopt(sock, level,	       \
> > +							   optname, optval,    \
> > +							   optlen);	       \
> > +	__ret;								       \
> > +})
> > +
> > +#define BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock, level, optname, optval, optlen)   \
> > +({									       \
> > +	int __ret = 0;							       \
> > +	if (cgroup_bpf_enabled)						       \
> > +		__ret = __cgroup_bpf_run_filter_getsockopt(sock, level,	       \
> > +							   optname, optval,    \
> > +							   optlen);	       \
> > +	__ret;								       \
> > +})
> > +
> >  int cgroup_bpf_prog_attach(const union bpf_attr *attr,
> >  			   enum bpf_prog_type ptype, struct bpf_prog *prog);
> >  int cgroup_bpf_prog_detach(const union bpf_attr *attr,
> > @@ -349,6 +376,8 @@ static inline int bpf_percpu_cgroup_storage_update(struct bpf_map *map,
> >  #define BPF_CGROUP_RUN_PROG_SOCK_OPS(sock_ops) ({ 0; })
> >  #define BPF_CGROUP_RUN_PROG_DEVICE_CGROUP(type,major,minor,access) ({ 0; })
> >  #define BPF_CGROUP_RUN_PROG_SYSCTL(head,table,write,buf,count,pos,nbuf) ({ 0; })
> > +#define BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock, level, optname, optval, optlen) ({ 0; })
> > +#define BPF_CGROUP_RUN_PROG_SETSOCKOPT(sock, level, optname, optval, optlen) ({ 0; })
> >  
> >  #define for_each_cgroup_storage_type(stype) for (; false; )
> >  
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index e5a309e6a400..883a190bc0b8 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -520,6 +520,7 @@ struct bpf_prog_array {
> >  struct bpf_prog_array *bpf_prog_array_alloc(u32 prog_cnt, gfp_t flags);
> >  void bpf_prog_array_free(struct bpf_prog_array *progs);
> >  int bpf_prog_array_length(struct bpf_prog_array *progs);
> > +bool bpf_prog_array_is_empty(struct bpf_prog_array *array);
> >  int bpf_prog_array_copy_to_user(struct bpf_prog_array *progs,
> >  				__u32 __user *prog_ids, u32 cnt);
> >  
> > @@ -606,6 +607,49 @@ _out:							\
> >  		_ret;					\
> >  	})
> >  
> > +/* To be used by BPF_PROG_TYPE_CGROUP_SOCKOPT program type.
> > + *
> > + * Expected BPF program return values are:
> > + *   0: return -EPERM to the userspace
> > + *   1: sockopt was not handled by BPF, kernel should do it
> > + *   2: sockopt was handled by BPF, kernel not should do it and return
> > + *      to the userspace instead
> > + *
> > + * Note, that return '0' takes precedence over everything else. In other
> > + * words, if any single program in the prog array has returned 0,
> > + * the userspace will get -EPERM (regardless of what other programs
> > + * return).
> > + *
> > + * The macro itself returns:
> > + *        0: sockopt was not handled by BPF, kernel should do it
> > + *        1: sockopt was handled by BPF, kernel snot hould do it
> > + *   -EPERM: return error back to userspace
> > + */
> > +#define BPF_PROG_CGROUP_SOCKOPT_RUN_ARRAY(array, ctx, func)		\
> > +	({								\
> > +		struct bpf_prog_array_item *_item;			\
> > +		struct bpf_prog *_prog;					\
> > +		struct bpf_prog_array *_array;				\
> > +		u32 ret;						\
> > +		u32 _success = 1;					\
> > +		u32 _bypass = 0;					\
> > +		preempt_disable();					\
> > +		rcu_read_lock();					\
> > +		_array = rcu_dereference(array);			\
> > +		_item = &_array->items[0];				\
> > +		while ((_prog = READ_ONCE(_item->prog))) {		\
> > +			bpf_cgroup_storage_set(_item->cgroup_storage);	\
> > +			ret = func(_prog, ctx);				\
> > +			_success &= (ret > 0);				\
> > +			_bypass |= (ret == 2);				\
> > +			_item++;					\
> > +		}							\
> > +		rcu_read_unlock();					\
> > +		preempt_enable();					\
> > +		ret = _success ? _bypass : -EPERM;			\
> > +		ret;							\
> > +	})
> > +
> >  #define BPF_PROG_RUN_ARRAY(array, ctx, func)		\
> >  	__BPF_PROG_RUN_ARRAY(array, ctx, func, false)
> >  
> > @@ -1054,6 +1098,8 @@ extern const struct bpf_func_proto bpf_spin_unlock_proto;
> >  extern const struct bpf_func_proto bpf_get_local_storage_proto;
> >  extern const struct bpf_func_proto bpf_strtol_proto;
> >  extern const struct bpf_func_proto bpf_strtoul_proto;
> > +extern const struct bpf_func_proto bpf_sk_fullsock_proto;
> > +extern const struct bpf_func_proto bpf_tcp_sock_proto;
> >  
> >  /* Shared helpers among cBPF and eBPF. */
> >  void bpf_user_rnd_init_once(void);
> > diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
> > index 5a9975678d6f..eec5aeeeaf92 100644
> > --- a/include/linux/bpf_types.h
> > +++ b/include/linux/bpf_types.h
> > @@ -30,6 +30,7 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE, raw_tracepoint_writable)
> >  #ifdef CONFIG_CGROUP_BPF
> >  BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_DEVICE, cg_dev)
> >  BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SYSCTL, cg_sysctl)
> > +BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SOCKOPT, cg_sockopt)
> >  #endif
> >  #ifdef CONFIG_BPF_LIRC_MODE2
> >  BPF_PROG_TYPE(BPF_PROG_TYPE_LIRC_MODE2, lirc_mode2)
> > diff --git a/include/linux/filter.h b/include/linux/filter.h
> > index 43b45d6db36d..6e64d01e4e36 100644
> > --- a/include/linux/filter.h
> > +++ b/include/linux/filter.h
> > @@ -1199,4 +1199,17 @@ struct bpf_sysctl_kern {
> >  	u64 tmp_reg;
> >  };
> >  
> > +struct bpf_sockopt_kern {
> > +	struct sock	*sk;
> > +	u8		*optval;
> > +	u8		*optval_end;
> > +	s32		level;
> > +	s32		optname;
> > +	u32		optlen;
> > +
> > +	/* Small on-stack optval buffer to avoid small allocations.
> > +	 */
> > +	u8 buf[64] __aligned(8);
> > +};
> > +
> >  #endif /* __LINUX_FILTER_H__ */
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 7c6aef253173..310b6bbfded8 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -170,6 +170,7 @@ enum bpf_prog_type {
> >  	BPF_PROG_TYPE_FLOW_DISSECTOR,
> >  	BPF_PROG_TYPE_CGROUP_SYSCTL,
> >  	BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE,
> > +	BPF_PROG_TYPE_CGROUP_SOCKOPT,
> >  };
> >  
> >  enum bpf_attach_type {
> > @@ -192,6 +193,8 @@ enum bpf_attach_type {
> >  	BPF_LIRC_MODE2,
> >  	BPF_FLOW_DISSECTOR,
> >  	BPF_CGROUP_SYSCTL,
> > +	BPF_CGROUP_GETSOCKOPT,
> > +	BPF_CGROUP_SETSOCKOPT,
> >  	__MAX_BPF_ATTACH_TYPE
> >  };
> >  
> > @@ -3533,4 +3536,15 @@ struct bpf_sysctl {
> >  				 */
> >  };
> >  
> > +struct bpf_sockopt {
> > +	__bpf_md_ptr(struct bpf_sock *, sk);
> > +
> > +	__s32	level;
> > +	__s32	optname;
> > +
> > +	__u32	optlen;
> > +	__u32	optval;
> > +	__u32	optval_end;
> After looking at patch 6, I think optval and optval_end should be changed
> to __bpf_md_ptr(void *, optval) and __bpf_md_ptr(void *, optval_end).
> That should avoid the (__u8 *)(long) casting in the bpf_prog.
Agreed, makes sense, will switch to __bpf_md_ptr. I had them as pointers
initially, but then switched to u32 for some reason.

> They need to be moved to the top of this struct.
> The is_valid_access() also needs to be adjusted on the size check.
> 
> "struct sk_msg_md" and "struct sk_reuseport_md" could be
> used as the examples.
> 
> > +};
> > +
> >  #endif /* _UAPI__LINUX_BPF_H__ */
> > diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
> > index 1b65ab0df457..04bc1a09464e 100644
> > --- a/kernel/bpf/cgroup.c
> > +++ b/kernel/bpf/cgroup.c
> > @@ -18,6 +18,7 @@
> >  #include <linux/bpf.h>
> >  #include <linux/bpf-cgroup.h>
> >  #include <net/sock.h>
> > +#include <net/bpf_sk_storage.h>
> >  
> >  DEFINE_STATIC_KEY_FALSE(cgroup_bpf_enabled_key);
> >  EXPORT_SYMBOL(cgroup_bpf_enabled_key);
> > @@ -924,6 +925,142 @@ int __cgroup_bpf_run_filter_sysctl(struct ctl_table_header *head,
> >  }
> >  EXPORT_SYMBOL(__cgroup_bpf_run_filter_sysctl);
> >  
> > +static bool __cgroup_bpf_prog_array_is_empty(struct cgroup *cgrp,
> > +					     enum bpf_attach_type attach_type)
> > +{
> > +	struct bpf_prog_array *prog_array;
> > +	bool empty;
> > +
> > +	rcu_read_lock();
> > +	prog_array = rcu_dereference(cgrp->bpf.effective[attach_type]);
> > +	empty = bpf_prog_array_is_empty(prog_array);
> > +	rcu_read_unlock();
> > +
> > +	return empty;
> > +}
> > +
> > +static int sockopt_alloc_buf(struct bpf_sockopt_kern *ctx, int max_optlen)
> > +{
> > +	if (unlikely(max_optlen > PAGE_SIZE))
> > +		return -EINVAL;
> > +
> > +	if (likely(max_optlen <= sizeof(ctx->buf))) {
> > +		ctx->optval = ctx->buf;
> > +	} else {
> > +		ctx->optval = kzalloc(max_optlen, GFP_USER);
> > +		if (!ctx->optval)
> > +			return -ENOMEM;
> > +	}
> > +
> > +	ctx->optval_end = ctx->optval + max_optlen;
> > +	ctx->optlen = max_optlen;
> > +
> > +	return 0;
> > +}
> > +
> > +static void sockopt_free_buf(struct bpf_sockopt_kern *ctx)
> > +{
> > +	if (unlikely(ctx->optval != ctx->buf))
> > +		kfree(ctx->optval);
> > +}
> > +
> > +int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int level,
> > +				       int optname, char __user *optval,
> > +				       unsigned int optlen)
> > +{
> > +	struct cgroup *cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
> > +	struct bpf_sockopt_kern ctx = {
> > +		.sk = sk,
> > +		.level = level,
> > +		.optname = optname,
> > +	};
> > +	int ret;
> > +
> > +	/* Opportunistic check to see whether we have any BPF program
> > +	 * attached to the hook so we don't waste time allocating
> > +	 * memory and locking the socket.
> > +	 */
> > +	if (__cgroup_bpf_prog_array_is_empty(cgrp, BPF_CGROUP_SETSOCKOPT))
> > +		return 0;
> > +
> > +	ret = sockopt_alloc_buf(&ctx, optlen);
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (copy_from_user(ctx.optval, optval, optlen) != 0) {
> > +		sockopt_free_buf(&ctx);
> > +		return -EFAULT;
> > +	}
> > +
> > +	lock_sock(sk);
> > +	ret = BPF_PROG_CGROUP_SOCKOPT_RUN_ARRAY(
> > +		cgrp->bpf.effective[BPF_CGROUP_SETSOCKOPT],
> > +		&ctx, BPF_PROG_RUN);
> > +	release_sock(sk);
> > +
> > +	sockopt_free_buf(&ctx);
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL(__cgroup_bpf_run_filter_setsockopt);
> > +
> > +int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level,
> > +				       int optname, char __user *optval,
> > +				       int __user *optlen)
> > +{
> > +	struct cgroup *cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);
> > +	struct bpf_sockopt_kern ctx = {
> > +		.sk = sk,
> > +		.level = level,
> > +		.optname = optname,
> > +	};
> > +	int max_optlen;
> > +	int ret;
> > +
> > +	/* Opportunistic check to see whether we have any BPF program
> > +	 * attached to the hook so we don't waste time allocating
> > +	 * memory and locking the socket.
> > +	 */
> > +	if (__cgroup_bpf_prog_array_is_empty(cgrp, BPF_CGROUP_GETSOCKOPT))
> > +		return 0;
> > +
> > +	if (get_user(max_optlen, optlen))
> > +		return -EFAULT;
> > +
> > +	ret = sockopt_alloc_buf(&ctx, max_optlen);
> > +	if (ret)
> > +		return ret;
> > +
> > +	lock_sock(sk);
> > +	ret = BPF_PROG_CGROUP_SOCKOPT_RUN_ARRAY(
> > +		cgrp->bpf.effective[BPF_CGROUP_GETSOCKOPT],
> > +		&ctx, BPF_PROG_RUN);
> > +	release_sock(sk);
> > +
> > +	if (ret < 0) {
> > +		sockopt_free_buf(&ctx);
> > +		return ret;
> > +	}
> > +
> > +	if (ctx.optlen > max_optlen) {
> > +		sockopt_free_buf(&ctx);
> > +		return -EFAULT;
> > +	}
> > +
> > +	if (copy_to_user(optval, ctx.optval, ctx.optlen) != 0) {
> > +		sockopt_free_buf(&ctx);
> > +		return -EFAULT;
> > +	}
> > +
> > +	sockopt_free_buf(&ctx);
> > +
> > +	if (put_user(ctx.optlen, optlen))
> > +		return -EFAULT;
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL(__cgroup_bpf_run_filter_getsockopt);
> > +
> >  static ssize_t sysctl_cpy_dir(const struct ctl_dir *dir, char **bufp,
> >  			      size_t *lenp)
> >  {
> > @@ -1184,3 +1321,143 @@ const struct bpf_verifier_ops cg_sysctl_verifier_ops = {
> >  
> >  const struct bpf_prog_ops cg_sysctl_prog_ops = {
> >  };
> > +
> > +static const struct bpf_func_proto *
> > +cg_sockopt_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> > +{
> > +	switch (func_id) {
> > +	case BPF_FUNC_sk_fullsock:
> > +		return &bpf_sk_fullsock_proto;
> > +	case BPF_FUNC_sk_storage_get:
> > +		return &bpf_sk_storage_get_proto;
> > +	case BPF_FUNC_sk_storage_delete:
> > +		return &bpf_sk_storage_delete_proto;
> > +#ifdef CONFIG_INET
> > +	case BPF_FUNC_tcp_sock:
> > +		return &bpf_tcp_sock_proto;
> > +#endif
> > +	default:
> > +		return cgroup_base_func_proto(func_id, prog);
> > +	}
> > +}
> > +
> > +static bool cg_sockopt_is_valid_access(int off, int size,
> > +				       enum bpf_access_type type,
> > +				       const struct bpf_prog *prog,
> > +				       struct bpf_insn_access_aux *info)
> > +{
> > +	const int size_default = sizeof(__u32);
> > +
> > +	if (off < 0 || off >= sizeof(struct bpf_sockopt))
> > +		return false;
> > +
> > +	if (off % size != 0)
> > +		return false;
> > +
> > +	if (type == BPF_WRITE) {
> > +		switch (off) {
> > +		case offsetof(struct bpf_sockopt, optlen):
> > +			if (size != size_default)
> > +				return false;
> > +			return prog->expected_attach_type ==
> > +				BPF_CGROUP_GETSOCKOPT;
> > +		default:
> > +			return false;
> > +		}
> > +	}
> > +
> > +	switch (off) {
> > +	case offsetof(struct bpf_sockopt, sk):
> > +		if (size != sizeof(__u64))
> > +			return false;
> > +		info->reg_type = PTR_TO_SOCKET;
> > +		break;
> > +	case bpf_ctx_range(struct bpf_sockopt, optval):
> > +		if (size != size_default)
> > +			return false;
> > +		info->reg_type = PTR_TO_PACKET;
> > +		break;
> > +	case bpf_ctx_range(struct bpf_sockopt, optval_end):
> > +		if (size != size_default)
> > +			return false;
> > +		info->reg_type = PTR_TO_PACKET_END;
> > +		break;
> > +	default:
> > +		if (size != size_default)
> > +			return false;
> > +		break;
> > +	}
> > +	return true;
> > +}
> > +
> > +static u32 cg_sockopt_convert_ctx_access(enum bpf_access_type type,
> > +					 const struct bpf_insn *si,
> > +					 struct bpf_insn *insn_buf,
> > +					 struct bpf_prog *prog,
> > +					 u32 *target_size)
> > +{
> > +	struct bpf_insn *insn = insn_buf;
> > +
> > +	switch (si->off) {
> > +	case offsetof(struct bpf_sockopt, sk):
> > +		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct
> > +						       bpf_sockopt_kern, sk),
> > +				      si->dst_reg, si->src_reg,
> > +				      offsetof(struct bpf_sockopt_kern, sk));
> > +		break;
> > +	case offsetof(struct bpf_sockopt, level):
> > +		*insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->src_reg,
> > +				      offsetof(struct bpf_sockopt_kern, level));
> > +		break;
> > +	case offsetof(struct bpf_sockopt, optname):
> > +		*insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->src_reg,
> Nit.
> May be also use BPF_FIELD_SIZEOF() for consistency.
> Same for a few BPF_W below.
My understanding was that we use BPF_FIELD_SIZEOF for pointers (where
the size might change on 32 vs 64 bits).
But sure, I can use it everywhere for consistency.

> > +				      offsetof(struct bpf_sockopt_kern,
> > +					       optname));
> > +		break;
> > +	case offsetof(struct bpf_sockopt, optlen):
> > +		if (type == BPF_WRITE)
> > +			*insn++ = BPF_STX_MEM(BPF_W, si->dst_reg, si->src_reg,
> > +					      offsetof(struct bpf_sockopt_kern,
> > +						       optlen));
> > +		else
> > +			*insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->src_reg,
> > +					      offsetof(struct bpf_sockopt_kern,
> > +						       optlen));
> > +		break;
> > +	case offsetof(struct bpf_sockopt, optval):
> > +		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct bpf_sockopt_kern,
> > +						       optval),
> > +				      si->dst_reg, si->src_reg,
> > +				      offsetof(struct bpf_sockopt_kern,
> > +					       optval));
> > +		break;
> > +	case offsetof(struct bpf_sockopt, optval_end):
> > +		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct bpf_sockopt_kern,
> > +						       optval_end),
> > +				      si->dst_reg, si->src_reg,
> > +				      offsetof(struct bpf_sockopt_kern,
> > +					       optval_end));
> > +		break;
> > +	}
> > +
> > +	return insn - insn_buf;
> > +}
> > +
> > +static int cg_sockopt_get_prologue(struct bpf_insn *insn_buf,
> > +				   bool direct_write,
> > +				   const struct bpf_prog *prog)
> > +{
> > +	/* Nothing to do for sockopt argument. The data is kzalloc'ated.
> > +	 */
> > +	return 0;
> > +}
> > +
> > +const struct bpf_verifier_ops cg_sockopt_verifier_ops = {
> > +	.get_func_proto		= cg_sockopt_func_proto,
> > +	.is_valid_access	= cg_sockopt_is_valid_access,
> > +	.convert_ctx_access	= cg_sockopt_convert_ctx_access,
> > +	.gen_prologue		= cg_sockopt_get_prologue,
> > +};
> > +
> > +const struct bpf_prog_ops cg_sockopt_prog_ops = {
> > +};
> 
> [ ... ]
> 
> > diff --git a/net/core/filter.c b/net/core/filter.c
> > index 55bfc941d17a..4652c0a005ca 100644
> > --- a/net/core/filter.c
> > +++ b/net/core/filter.c
> > @@ -1835,7 +1835,7 @@ BPF_CALL_1(bpf_sk_fullsock, struct sock *, sk)
> >  	return sk_fullsock(sk) ? (unsigned long)sk : (unsigned long)NULL;
> >  }
> >  
> > -static const struct bpf_func_proto bpf_sk_fullsock_proto = {
> > +const struct bpf_func_proto bpf_sk_fullsock_proto = {
> Exposing this is no longer needed.  PTR_TO_SOCKET is already a fullsock.
> 
> >  	.func		= bpf_sk_fullsock,
> >  	.gpl_only	= false,
> >  	.ret_type	= RET_PTR_TO_SOCKET_OR_NULL,
> > @@ -5636,7 +5636,7 @@ BPF_CALL_1(bpf_tcp_sock, struct sock *, sk)
> >  	return (unsigned long)NULL;
> >  }
> >