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_has_prog_array that exits early if there is nothing attached to a cgroup. Note, however, that there is a race between __cgroup_bpf_has_prog_array 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. By default, kernel code path is executed after the hook (to let BPF handle only a subset of the options). There is new bpf_sockopt_handled handler that returns control to the userspace instead (bypassing the kernel handling). The return code is either 1 (success) or 0 (EPERM). Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxx> --- include/linux/bpf-cgroup.h | 29 ++++ include/linux/bpf.h | 2 + include/linux/bpf_types.h | 1 + include/linux/filter.h | 19 +++ include/uapi/linux/bpf.h | 17 ++- kernel/bpf/cgroup.c | 288 +++++++++++++++++++++++++++++++++++++ kernel/bpf/syscall.c | 19 +++ kernel/bpf/verifier.c | 12 ++ net/core/filter.c | 4 +- net/socket.c | 18 +++ 10 files changed, 406 insertions(+), 3 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..fb4e6ef5a971 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1054,6 +1054,8 @@ 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..7a07fd2e14d3 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -1199,4 +1199,23 @@ struct bpf_sysctl_kern { u64 tmp_reg; }; +struct bpf_sockopt_kern { + struct sock *sk; + s32 level; + s32 optname; + u32 optlen; + u8 *optval; + u8 *optval_end; + + /* If true, BPF program had consumed the sockopt request. + * Control is returned to the userspace (i.e. kernel doesn't + * handle this option). + */ + bool handled; + + /* Small on-stack optval buffer to avoid small allocations. + */ + u8 buf[64]; +}; + #endif /* __LINUX_FILTER_H__ */ diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 7c6aef253173..b6c3891241ef 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 }; @@ -2815,7 +2818,8 @@ union bpf_attr { FN(strtoul), \ FN(sk_storage_get), \ FN(sk_storage_delete), \ - FN(send_signal), + FN(send_signal), \ + FN(sockopt_handled), /* integer value in 'imm' field of BPF_CALL instruction selects which helper * function eBPF program intends to call @@ -3533,4 +3537,15 @@ 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..4ec99ea97023 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_has_prog_array(struct cgroup *cgrp, + enum bpf_attach_type attach_type) +{ + struct bpf_prog_array *prog_array; + int nr; + + rcu_read_lock(); + prog_array = rcu_dereference(cgrp->bpf.effective[attach_type]); + nr = bpf_prog_array_length(prog_array); + rcu_read_unlock(); + + return nr > 0; +} + +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_has_prog_array(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_RUN_ARRAY(cgrp->bpf.effective[BPF_CGROUP_SETSOCKOPT], + &ctx, BPF_PROG_RUN); + release_sock(sk); + + sockopt_free_buf(&ctx); + + if (!ret) + return -EPERM; + + return ctx.handled ? 1 : 0; +} +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; + char buf[64]; + 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_has_prog_array(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_RUN_ARRAY(cgrp->bpf.effective[BPF_CGROUP_GETSOCKOPT], + &ctx, BPF_PROG_RUN); + release_sock(sk); + + 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; + + if (!ret) + return -EPERM; + + return ctx.handled ? 1 : 0; +} +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 +1321,154 @@ const struct bpf_verifier_ops cg_sysctl_verifier_ops = { const struct bpf_prog_ops cg_sysctl_prog_ops = { }; + +BPF_CALL_1(bpf_sockopt_handled, struct bpf_sockopt_kern *, ctx) +{ + ctx->handled = true; + return 1; +} + +static const struct bpf_func_proto bpf_sockopt_handled_proto = { + .func = bpf_sockopt_handled, + .gpl_only = false, + .arg1_type = ARG_PTR_TO_CTX, + .ret_type = RET_INTEGER, +}; + +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_sockopt_handled: + return &bpf_sockopt_handled_proto; + 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_SOCK_COMMON_OR_NULL; + 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, + bpf_target_off(struct bpf_sockopt_kern, + level, 4, target_size)); + break; + case offsetof(struct bpf_sockopt, optname): + *insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->src_reg, + bpf_target_off(struct bpf_sockopt_kern, + optname, 4, target_size)); + break; + case offsetof(struct bpf_sockopt, optlen): + if (type == BPF_WRITE) + *insn++ = BPF_STX_MEM(BPF_W, si->dst_reg, si->src_reg, + bpf_target_off(struct bpf_sockopt_kern, + optlen, 4, target_size)); + else + *insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->src_reg, + bpf_target_off(struct bpf_sockopt_kern, + optlen, 4, target_size)); + 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/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..b91fde10e721 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; } 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