diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 839dd8670a7a..50e5c4b52bd1 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -768,6 +768,8 @@ struct bpf_prog_aux { struct mutex dst_mutex; /* protects dst_* pointers below, *after* prog becomes visible */ struct bpf_prog *dst_prog; struct bpf_trampoline *dst_trampoline; + enum bpf_prog_type saved_dst_prog_type; + enum bpf_attach_type saved_dst_attach_type; bool verifier_zext; /* Zero extensions has been inserted by verifier. */ bool offload_requested; bool attach_btf_trace; /* true if attaching to BTF-enabled raw tp */ diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 96ddb00b91dc..2b1d3f16cbd1 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -639,8 +639,13 @@ union bpf_attr { }; __u32 attach_type; /* attach type */ __u32 flags; /* extra flags */ - __aligned_u64 iter_info; /* extra bpf_iter_link_info */ - __u32 iter_info_len; /* iter_info length */ + union { + __u32 target_btf_id; /* btf_id of target to attach to */ + struct { + __aligned_u64 iter_info; /* extra bpf_iter_link_info */ + __u32 iter_info_len; /* iter_info length */ + }; + }; } link_create; struct { /* struct used by BPF_LINK_UPDATE command */ diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index e6a0a948e30c..f1528c2a6927 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -4,6 +4,7 @@ #include #include #include +#include #include #include #include @@ -2554,12 +2555,15 @@ static const struct bpf_link_ops bpf_tracing_link_lops = { .fill_link_info = bpf_tracing_link_fill_link_info, }; -static int bpf_tracing_prog_attach(struct bpf_prog *prog) +static int bpf_tracing_prog_attach(struct bpf_prog *prog, + int tgt_prog_fd, + u32 btf_id) { struct bpf_link_primer link_primer; struct bpf_prog *tgt_prog = NULL; + struct bpf_trampoline *tr = NULL; struct bpf_tracing_link *link; - struct bpf_trampoline *tr; + u64 key = 0; int err; switch (prog->type) { @@ -2588,6 +2592,28 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog) goto out_put_prog; } + if (!!tgt_prog_fd != !!btf_id) { + err = -EINVAL; + goto out_put_prog; + } + + if (tgt_prog_fd) { + /* For now we only allow new targets for BPF_PROG_TYPE_EXT */ + if (prog->type != BPF_PROG_TYPE_EXT) { + err = -EINVAL; + goto out_put_prog; + } + + tgt_prog = bpf_prog_get(tgt_prog_fd); + if (IS_ERR(tgt_prog)) { + err = PTR_ERR(tgt_prog); + tgt_prog = NULL; + goto out_put_prog; + } + + key = bpf_trampoline_compute_key(tgt_prog, btf_id); + } + link = kzalloc(sizeof(*link), GFP_USER); if (!link) { err = -ENOMEM; @@ -2599,12 +2625,58 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog) mutex_lock(&prog->aux->dst_mutex); - if (!prog->aux->dst_trampoline) { + /* There are a few possible cases here: + * + * - if prog->aux->dst_trampoline is set, the program was just loaded + * and not yet attached to anything, so we can use the values stored + * in prog->aux + * + * - if prog->aux->dst_trampoline is NULL, the program has already been + * attached to a target and its initial target was cleared (below) + * + * - if tgt_prog != NULL, the caller specified tgt_prog_fd + + * target_btf_id using the link_create API. + * + * - if tgt_prog == NULL when this function was called using the old + * raw_tracepoint_open API, and we need a target from prog->aux + * + * The combination of no saved target in prog->aux, and no target + * specified on load is illegal, and we reject that here. + */ + if (!prog->aux->dst_trampoline && !tgt_prog) { err = -ENOENT; goto out_unlock; } - tr = prog->aux->dst_trampoline; - tgt_prog = prog->aux->dst_prog; + + if (!prog->aux->dst_trampoline || + (key && key != prog->aux->dst_trampoline->key)) { + /* If there is no saved target, or the specified target is + * different from the destination specified at load time, we + * need a new trampoline and a check for compatibility + */ + struct bpf_attach_target_info tgt_info = {}; + + err = bpf_check_attach_target(NULL, prog, tgt_prog, btf_id, + &tgt_info); + if (err) + goto out_unlock; + + tr = bpf_trampoline_get(key, &tgt_info); + if (!tr) { + err = -ENOMEM; + goto out_unlock; + } + } else { + /* The caller didn't specify a target, or the target was the + * same as the destination supplied during program load. This + * means we can reuse the trampoline and reference from program + * load time, and there is no need to allocate a new one. This + * can only happen once for any program, as the saved values in + * prog->aux are cleared below. + */ + tr = prog->aux->dst_trampoline; + tgt_prog = prog->aux->dst_prog; + } err = bpf_link_prime(&link->link, &link_primer); if (err) @@ -2620,15 +2692,31 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog) link->tgt_prog = tgt_prog; link->trampoline = tr; + /* Always clear the trampoline and target prog from prog->aux to make + * sure the original attach destination is not kept alive after a + * program is (re-)attached to another target. + */ + if (prog->aux->dst_prog && + (tgt_prog_fd || tr != prog->aux->dst_trampoline)) + /* got extra prog ref from syscall, or attaching to different prog */ + bpf_prog_put(prog->aux->dst_prog); + if (prog->aux->dst_trampoline && tr != prog->aux->dst_trampoline) + /* we allocated a new trampoline, so free the old one */ + bpf_trampoline_put(prog->aux->dst_trampoline); + prog->aux->dst_prog = NULL; prog->aux->dst_trampoline = NULL; mutex_unlock(&prog->aux->dst_mutex); return bpf_link_settle(&link_primer); out_unlock: + if (tr && tr != prog->aux->dst_trampoline) + bpf_trampoline_put(tr); mutex_unlock(&prog->aux->dst_mutex); kfree(link); out_put_prog: + if (tgt_prog_fd && tgt_prog) + bpf_prog_put(tgt_prog); bpf_prog_put(prog); return err; } @@ -2742,7 +2830,7 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr) tp_name = prog->aux->attach_func_name; break; } - return bpf_tracing_prog_attach(prog); + return bpf_tracing_prog_attach(prog, 0, 0); case BPF_PROG_TYPE_RAW_TRACEPOINT: case BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE: if (strncpy_from_user(buf, @@ -3926,10 +4014,15 @@ err_put: static int tracing_bpf_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) { - if (attr->link_create.attach_type == BPF_TRACE_ITER && - prog->expected_attach_type == BPF_TRACE_ITER) - return bpf_iter_link_attach(attr, prog); + if (attr->link_create.attach_type != prog->expected_attach_type) + return -EINVAL; + if (prog->expected_attach_type == BPF_TRACE_ITER) + return bpf_iter_link_attach(attr, prog); + else if (prog->type == BPF_PROG_TYPE_EXT) + return bpf_tracing_prog_attach(prog, + attr->link_create.target_fd, + attr->link_create.target_btf_id); return -EINVAL; } @@ -3943,18 +4036,25 @@ static int link_create(union bpf_attr *attr) if (CHECK_ATTR(BPF_LINK_CREATE)) return -EINVAL; - ptype = attach_type_to_prog_type(attr->link_create.attach_type); - if (ptype == BPF_PROG_TYPE_UNSPEC) - return -EINVAL; - - prog = bpf_prog_get_type(attr->link_create.prog_fd, ptype); + prog = bpf_prog_get(attr->link_create.prog_fd); if (IS_ERR(prog)) return PTR_ERR(prog); ret = bpf_prog_attach_check_attach_type(prog, attr->link_create.attach_type); if (ret) - goto err_out; + goto out; + + if (prog->type == BPF_PROG_TYPE_EXT) { + ret = tracing_bpf_link_attach(attr, prog); + goto out; + } + + ptype = attach_type_to_prog_type(attr->link_create.attach_type); + if (ptype == BPF_PROG_TYPE_UNSPEC || ptype != prog->type) { + ret = -EINVAL; + goto out; + } switch (ptype) { case BPF_PROG_TYPE_CGROUP_SKB: @@ -3982,7 +4082,7 @@ static int link_create(union bpf_attr *attr) ret = -EINVAL; } -err_out: +out: if (ret < 0) bpf_prog_put(prog); return ret; diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index a97a2f2964e3..015a1c074b6b 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -11404,6 +11404,11 @@ int bpf_check_attach_target(struct bpf_verifier_log *log, if (!btf_type_is_func_proto(t)) return -EINVAL; + if ((prog->aux->saved_dst_prog_type || prog->aux->saved_dst_attach_type) && + (!tgt_prog || prog->aux->saved_dst_prog_type != tgt_prog->type || + prog->aux->saved_dst_attach_type != tgt_prog->expected_attach_type)) + return -EINVAL; + if (tgt_prog && conservative) t = NULL; @@ -11512,6 +11517,11 @@ static int check_attach_btf_id(struct bpf_verifier_env *env) prog->aux->attach_func_proto = tgt_info.tgt_type; prog->aux->attach_func_name = tgt_info.tgt_name; + if (tgt_prog) { + prog->aux->saved_dst_prog_type = tgt_prog->type; + prog->aux->saved_dst_attach_type = tgt_prog->expected_attach_type; + } + if (prog->expected_attach_type == BPF_TRACE_RAW_TP) { prog->aux->attach_btf_trace = true; return 0; diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 96ddb00b91dc..2b1d3f16cbd1 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -639,8 +639,13 @@ union bpf_attr { }; __u32 attach_type; /* attach type */ __u32 flags; /* extra flags */ - __aligned_u64 iter_info; /* extra bpf_iter_link_info */ - __u32 iter_info_len; /* iter_info length */ + union { + __u32 target_btf_id; /* btf_id of target to attach to */ + struct { + __aligned_u64 iter_info; /* extra bpf_iter_link_info */ + __u32 iter_info_len; /* iter_info length */ + }; + }; } link_create; struct { /* struct used by BPF_LINK_UPDATE command */