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

From: Stanislav Fomichev <[email-masked]>
Date: Thu, 6 Jun 2019 15:27:29 -0700

On 06/06, Andrii Nakryiko wrote:
> On Thu, Jun 6, 2019 at 12:03 PM Stanislav Fomichev <[email-masked]> 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
> 
> typo: should not do it?
Sigh, good catch, thanks!

> > + *      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
> 
> typo: "snot hould do it" -> "shouldn't do it"?
Ditto.

> > + *   -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;                                        \
> 
> reverse Christmas tree? or it's not enforced in a macro?
I don't think we do that for other BPF_PROG_XXX_RUN_ARRAY
handlers. But sure, why not? :-)

> > +               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;
> > +};
> > +
> >  #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;
> > +       }
> 
> So this is the case where BPF program returns value that's bigger than
> a buffer provided by users? Existing code in sock_getsockopt handles
> that by filling out only first N bytes, instead of failing. Should the
> behavior be the same here?
I'm not sure. BPF program would need to handle this case anyway, right?
Verifier would not let it put more bytes in the buffer than available,
so increasing optlen in the BPF program doesn't really make sense.
It feels like returning a EPERM (and assuming BPF program is buggy)
is safer. Am I missing something?

> > +       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,
> > +                                     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/kernel/bpf/core.c b/kernel/bpf/core.c
> > index 33fb292f2e30..e9152ebd66bc 100644
> > --- a/kernel/bpf/core.c
> > +++ b/kernel/bpf/core.c
> > @@ -1813,6 +1813,15 @@ int bpf_prog_array_length(struct bpf_prog_array *array)
> >         return cnt;
> >  }
> >
> > +bool bpf_prog_array_is_empty(struct bpf_prog_array *array)
> > +{
> > +       struct bpf_prog_array_item *item;
> > +
> > +       for (item = array->items; item->prog; item++)
> > +               if (item->prog != &dummy_bpf_prog.prog)
> > +                       return false;
> > +       return true;
> > +}
> >
> >  static bool bpf_prog_array_copy_core(struct bpf_prog_array *array,
> >                                      u32 *prog_ids,
> > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> > index 4c53cbd3329d..4ad2b5f1905f 100644
> > --- a/kernel/bpf/syscall.c
> > +++ b/kernel/bpf/syscall.c
> > @@ -1596,6 +1596,14 @@ bpf_prog_load_check_attach_type(enum bpf_prog_type prog_type,
> >                 default:
> >                         return -EINVAL;
> >                 }
> > +       case BPF_PROG_TYPE_CGROUP_SOCKOPT:
> > +               switch (expected_attach_type) {
> > +               case BPF_CGROUP_SETSOCKOPT:
> > +               case BPF_CGROUP_GETSOCKOPT:
> > +                       return 0;
> > +               default:
> > +                       return -EINVAL;
> > +               }
> >         default:
> >                 return 0;
> >         }
> > @@ -1846,6 +1854,7 @@ static int bpf_prog_attach_check_attach_type(const struct bpf_prog *prog,
> >         switch (prog->type) {
> >         case BPF_PROG_TYPE_CGROUP_SOCK:
> >         case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
> > +       case BPF_PROG_TYPE_CGROUP_SOCKOPT:
> >                 return attach_type == prog->expected_attach_type ? 0 : -EINVAL;
> >         case BPF_PROG_TYPE_CGROUP_SKB:
> >                 return prog->enforce_expected_attach_type &&
> > @@ -1916,6 +1925,10 @@ static int bpf_prog_attach(const union bpf_attr *attr)
> >         case BPF_CGROUP_SYSCTL:
> >                 ptype = BPF_PROG_TYPE_CGROUP_SYSCTL;
> >                 break;
> > +       case BPF_CGROUP_GETSOCKOPT:
> > +       case BPF_CGROUP_SETSOCKOPT:
> > +               ptype = BPF_PROG_TYPE_CGROUP_SOCKOPT;
> > +               break;
> >         default:
> >                 return -EINVAL;
> >         }
> > @@ -1997,6 +2010,10 @@ static int bpf_prog_detach(const union bpf_attr *attr)
> >         case BPF_CGROUP_SYSCTL:
> >                 ptype = BPF_PROG_TYPE_CGROUP_SYSCTL;
> >                 break;
> > +       case BPF_CGROUP_GETSOCKOPT:
> > +       case BPF_CGROUP_SETSOCKOPT:
> > +               ptype = BPF_PROG_TYPE_CGROUP_SOCKOPT;
> > +               break;
> >         default:
> >                 return -EINVAL;
> >         }
> > @@ -2031,6 +2048,8 @@ static int bpf_prog_query(const union bpf_attr *attr,
> >         case BPF_CGROUP_SOCK_OPS:
> >         case BPF_CGROUP_DEVICE:
> >         case BPF_CGROUP_SYSCTL:
> > +       case BPF_CGROUP_GETSOCKOPT:
> > +       case BPF_CGROUP_SETSOCKOPT:
> >                 break;
> >         case BPF_LIRC_MODE2:
> >                 return lirc_prog_query(attr, uattr);
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index 5c2cb5bd84ce..fffc668ef536 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -1717,6 +1717,18 @@ static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
> >
> >                 env->seen_direct_write = true;
> >                 return true;
> > +
> > +       case BPF_PROG_TYPE_CGROUP_SOCKOPT:
> > +               if (t == BPF_WRITE) {
> > +                       if (env->prog->expected_attach_type ==
> > +                           BPF_CGROUP_GETSOCKOPT) {
> > +                               env->seen_direct_write = true;
> > +                               return true;
> > +                       }
> > +                       return false;
> > +               }
> > +               return true;
> > +
> >         default:
> >                 return false;
> >         }
> > @@ -5524,6 +5536,9 @@ static int check_return_code(struct bpf_verifier_env *env)
> >         case BPF_PROG_TYPE_CGROUP_DEVICE:
> >         case BPF_PROG_TYPE_CGROUP_SYSCTL:
> >                 break;
> > +       case BPF_PROG_TYPE_CGROUP_SOCKOPT:
> > +               range = tnum_range(0, 2);
> > +               break;
> >         default:
> >                 return 0;
> >         }
> > 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 = {
> >         .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;
> >  }
> >
> > -static const struct bpf_func_proto bpf_tcp_sock_proto = {
> > +const struct bpf_func_proto bpf_tcp_sock_proto = {
> >         .func           = bpf_tcp_sock,
> >         .gpl_only       = false,
> >         .ret_type       = RET_PTR_TO_TCP_SOCK_OR_NULL,
> > diff --git a/net/socket.c b/net/socket.c
> > index 72372dc5dd70..e8654f1f70e6 100644
> > --- a/net/socket.c
> > +++ b/net/socket.c
> > @@ -2069,6 +2069,15 @@ static int __sys_setsockopt(int fd, int level, int optname,
> >                 if (err)
> >                         goto out_put;
> >
> > +               err = BPF_CGROUP_RUN_PROG_SETSOCKOPT(sock->sk, level, optname,
> > +                                                    optval, optlen);
> > +               if (err < 0) {
> > +                       goto out_put;
> > +               } else if (err > 0) {
> > +                       err = 0;
> > +                       goto out_put;
> > +               }
> > +
> >                 if (level == SOL_SOCKET)
> >                         err =
> >                             sock_setsockopt(sock, level, optname, optval,
> > @@ -2106,6 +2115,15 @@ static int __sys_getsockopt(int fd, int level, int optname,
> >                 if (err)
> >                         goto out_put;
> >
> > +               err = BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock->sk, level, optname,
> > +                                                    optval, optlen);
> > +               if (err < 0) {
> > +                       goto out_put;
> > +               } else if (err > 0) {
> > +                       err = 0;
> > +                       goto out_put;
> > +               }
> > +
> >                 if (level == SOL_SOCKET)
> >                         err =
> >                             sock_getsockopt(sock, level, optname, optval,
> > --
> > 2.22.0.rc1.311.g5d7573a151-goog
> >