From patchwork Tue Jan 4 17:15:04 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: YiFei Zhu X-Patchwork-Id: 12703718 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4D130C433EF for ; Tue, 4 Jan 2022 17:15:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231168AbiADRPb (ORCPT ); Tue, 4 Jan 2022 12:15:31 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36804 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234364AbiADRPY (ORCPT ); Tue, 4 Jan 2022 12:15:24 -0500 Received: from mail-pf1-x449.google.com (mail-pf1-x449.google.com [IPv6:2607:f8b0:4864:20::449]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C7A52C061799 for ; Tue, 4 Jan 2022 09:15:24 -0800 (PST) Received: by mail-pf1-x449.google.com with SMTP id t29-20020aa7947d000000b004bb4bd3dd77so18434893pfq.0 for ; Tue, 04 Jan 2022 09:15:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=bSExvyKcUDN4Il5vWcei6QEaGbWqpD9OrKIwdpgjomw=; b=DraPTFOFxjGp1+lP5yiiyCYoQxiUVImg7iUGnM78tcMDanr7BiGKcr5jFHmGJ7I30U uaUpGj6con/YWK3h1nLIXkr7oioDp4tBHOsBJuGSbHYVxpI9fsD37AqjXkt98dN+zjCw s2qNMAo9sFRL2xzEObWz90MPlMTxCTuELp3oQGusaRG9woAR7/DVNhJSY5hvRZttlOLE 6lV/KO2GG8WBGUFiPIGtbUJHYQi25S1n+RJ+WwUvrv4GlfFOz52EbnkwTSNk8BxqtePF Cl1rJnm6oQLSQ5QwOnVOXERED0r3MNVYrUClVQQtFJYkMkmD6ACo4NctdJVKy1yOVpKp TXYw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=bSExvyKcUDN4Il5vWcei6QEaGbWqpD9OrKIwdpgjomw=; b=oRu6UpvKx6dyXKFXTCRjv15Oz4C3HUh621XCLthNTg8odgOJdfnFF///wdzw4SSk78 a//tRNEB6Z0CyRmBWbrbNLCF1KyUnCEzeomm9Sagzif8Bke4OyS7yBb8l8ud4JoTwGqv 7PqbS2ne6QZlW3QXYBIuMF5sKUMTvBwe3UBLbPOmfp7cR5aPJJstL4uxQdd3Bgpw89ck vdcFW3PJobuCENA+15xxxuJB1U7kS2EgIeE+zAM9XuPQGRlVM2n0yo37o5vc5YoQT+iU cvKoKA3BV4wrbRlL43/TqxWuXSrGC33R1w8BulzLFxNFPdmMHfJxDA9HU116BytMml7i Z/CQ== X-Gm-Message-State: AOAM532MYAsIBHVO9j+NBaHkI0zy8u1BP7cLYhtEA9KW61NoctA1ZbMT B1URvNtu3SAQdzlx4LM8jYPFoNg6AF43JmIYBvupbYX/vli7lO8kaoszX6ewZjyZb0mFJGHL2zf W2d0ewsWfODUkgozEEuVF/Jhb45zMxbgHzMdq6TVB0JWLCDxdsvN1slL2kYL//mM= X-Google-Smtp-Source: ABdhPJx/L6wqY3HzALz3xjgtS69Wabn9JEdtQPYiXpM4MXL5hOhoqu3bK99FUz66KEsHKWQvJbEOTO6N9gB1HA== X-Received: from zhuyifei-kvm.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:2edc]) (user=zhuyifei job=sendgmr) by 2002:a62:ea11:0:b0:4bc:9be8:9b2a with SMTP id t17-20020a62ea11000000b004bc9be89b2amr12545993pfh.64.1641316524013; Tue, 04 Jan 2022 09:15:24 -0800 (PST) Date: Tue, 4 Jan 2022 17:15:04 +0000 In-Reply-To: Message-Id: <833b122afaeaba4485942c563ef16a64fa997fe6.1641316155.git.zhuyifei@google.com> Mime-Version: 1.0 References: X-Mailer: git-send-email 2.34.1.448.ga2b2bfdf31-goog Subject: [PATCH v3 bpf-next 3/4] bpf: Add cgroup helpers bpf_{get,set}_retval to get/set syscall return value From: YiFei Zhu To: bpf@vger.kernel.org Cc: Stanislav Fomichev , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Song Liu , YiFei Zhu Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net The helpers continue to use int for retval because all the hooks are int-returning rather than long-returning. The return value of bpf_set_retval is int for future-proofing, in case in the future there may be errors trying to set the retval. After the previous patch, if a program rejects a syscall by returning 0, an -EPERM will be generated no matter if the retval is already set to -err. This patch change it being forced only if retval is not -err. This is because we want to support, for example, invoking bpf_set_retval(-EINVAL) and return 0, and have the syscall return value be -EINVAL not -EPERM. This change is reflected in the sockopt_sk test which has been updated to assert the errno is EINVAL instead of the EPERM. The eBPF prog has to explicitly bpf_set_retval(-EPERM) if EPERM is wanted. I also removed the explicit mentions of EPERM in the comments in the prog. For BPF_PROG_CGROUP_INET_EGRESS_RUN_ARRAY, the prior behavior is that, if the return value is NET_XMIT_DROP, the packet is silently dropped. We preserve this behavior for backward compatibility reasons, so even if an errno is set, the errno does not return to caller. However, setting a non-err to retval cannot propagate so this is not allowed and we return a -EFAULT in that case. Signed-off-by: YiFei Zhu Reviewed-by: Stanislav Fomichev --- include/linux/bpf.h | 10 +++-- include/uapi/linux/bpf.h | 18 +++++++++ kernel/bpf/cgroup.c | 38 ++++++++++++++++++- tools/include/uapi/linux/bpf.h | 18 +++++++++ .../selftests/bpf/prog_tests/sockopt_sk.c | 2 +- .../testing/selftests/bpf/progs/sockopt_sk.c | 32 ++++++++-------- 6 files changed, 96 insertions(+), 22 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 88f6891e2b53..300df48fa0e0 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1300,7 +1300,7 @@ BPF_PROG_RUN_ARRAY_CG_FLAGS(const struct bpf_prog_array __rcu *array_rcu, while ((prog = READ_ONCE(item->prog))) { run_ctx.prog_item = item; func_ret = run_prog(prog, ctx); - if (!(func_ret & 1)) + if (!(func_ret & 1) && !IS_ERR_VALUE((long)run_ctx.retval)) run_ctx.retval = -EPERM; *(ret_flags) |= (func_ret >> 1); item++; @@ -1330,7 +1330,7 @@ BPF_PROG_RUN_ARRAY_CG(const struct bpf_prog_array __rcu *array_rcu, old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx); while ((prog = READ_ONCE(item->prog))) { run_ctx.prog_item = item; - if (!run_prog(prog, ctx)) + if (!run_prog(prog, ctx) && !IS_ERR_VALUE((long)run_ctx.retval)) run_ctx.retval = -EPERM; item++; } @@ -1390,7 +1390,7 @@ BPF_PROG_RUN_ARRAY(const struct bpf_prog_array __rcu *array_rcu, * 0: NET_XMIT_SUCCESS skb should be transmitted * 1: NET_XMIT_DROP skb should be dropped and cn * 2: NET_XMIT_CN skb should be transmitted and cn - * 3: -EPERM skb should be dropped + * 3: -err skb should be dropped */ #define BPF_PROG_CGROUP_INET_EGRESS_RUN_ARRAY(array, ctx, func) \ ({ \ @@ -1399,10 +1399,12 @@ BPF_PROG_RUN_ARRAY(const struct bpf_prog_array __rcu *array_rcu, u32 _ret; \ _ret = BPF_PROG_RUN_ARRAY_CG_FLAGS(array, ctx, func, 0, &_flags); \ _cn = _flags & BPF_RET_SET_CN; \ + if (_ret && !IS_ERR_VALUE((long)_ret)) \ + _ret = -EFAULT; \ if (!_ret) \ _ret = (_cn ? NET_XMIT_CN : NET_XMIT_SUCCESS); \ else \ - _ret = (_cn ? NET_XMIT_DROP : -EPERM); \ + _ret = (_cn ? NET_XMIT_DROP : _ret); \ _ret; \ }) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index b0383d371b9a..140702c56938 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -5018,6 +5018,22 @@ union bpf_attr { * * Return * The number of arguments of the traced function. + * + * int bpf_get_retval(void) + * Description + * Get the syscall's return value that will be returned to userspace. + * + * This helper is currently supported by cgroup programs only. + * Return + * The syscall's return value. + * + * int bpf_set_retval(int retval) + * Description + * Set the syscall's return value that will be returned to userspace. + * + * This helper is currently supported by cgroup programs only. + * Return + * 0 on success, or a negative error in case of failure. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -5206,6 +5222,8 @@ union bpf_attr { FN(get_func_arg), \ FN(get_func_ret), \ FN(get_func_arg_cnt), \ + FN(get_retval), \ + FN(set_retval), \ /* */ /* integer value in 'imm' field of BPF_CALL instruction selects which helper diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index b6fad0bbf5a7..279ebbed75a5 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -1044,7 +1044,7 @@ int cgroup_bpf_prog_query(const union bpf_attr *attr, * NET_XMIT_DROP (1) - drop packet and notify TCP to call cwr * NET_XMIT_CN (2) - continue with packet output and notify TCP * to call cwr - * -EPERM - drop packet + * -err - drop packet * * For ingress packets, this function will return -EPERM if any * attached program was found and if it returned != 1 during execution. @@ -1080,6 +1080,8 @@ int __cgroup_bpf_run_filter_skb(struct sock *sk, } else { ret = BPF_PROG_RUN_ARRAY_CG(cgrp->bpf.effective[atype], skb, __bpf_prog_run_save_cb, 0); + if (ret && !IS_ERR_VALUE((long)ret)) + ret = -EFAULT; } bpf_restore_data_end(skb, saved_data_end); __skb_pull(skb, offset); @@ -1205,6 +1207,36 @@ int __cgroup_bpf_check_dev_permission(short dev_type, u32 major, u32 minor, return ret; } +BPF_CALL_0(bpf_get_retval) +{ + struct bpf_cg_run_ctx *ctx = + container_of(current->bpf_ctx, struct bpf_cg_run_ctx, run_ctx); + + return ctx->retval; +} + +static const struct bpf_func_proto bpf_get_retval_proto = { + .func = bpf_get_retval, + .gpl_only = false, + .ret_type = RET_INTEGER, +}; + +BPF_CALL_1(bpf_set_retval, int, retval) +{ + struct bpf_cg_run_ctx *ctx = + container_of(current->bpf_ctx, struct bpf_cg_run_ctx, run_ctx); + + ctx->retval = retval; + return 0; +} + +static const struct bpf_func_proto bpf_set_retval_proto = { + .func = bpf_set_retval, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_ANYTHING, +}; + static const struct bpf_func_proto * cgroup_base_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) { @@ -1217,6 +1249,10 @@ cgroup_base_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_get_current_cgroup_id_proto; case BPF_FUNC_perf_event_output: return &bpf_event_output_data_proto; + case BPF_FUNC_get_retval: + return &bpf_get_retval_proto; + case BPF_FUNC_set_retval: + return &bpf_set_retval_proto; default: return bpf_base_func_proto(func_id); } diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index b0383d371b9a..140702c56938 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -5018,6 +5018,22 @@ union bpf_attr { * * Return * The number of arguments of the traced function. + * + * int bpf_get_retval(void) + * Description + * Get the syscall's return value that will be returned to userspace. + * + * This helper is currently supported by cgroup programs only. + * Return + * The syscall's return value. + * + * int bpf_set_retval(int retval) + * Description + * Set the syscall's return value that will be returned to userspace. + * + * This helper is currently supported by cgroup programs only. + * Return + * 0 on success, or a negative error in case of failure. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -5206,6 +5222,8 @@ union bpf_attr { FN(get_func_arg), \ FN(get_func_ret), \ FN(get_func_arg_cnt), \ + FN(get_retval), \ + FN(set_retval), \ /* */ /* integer value in 'imm' field of BPF_CALL instruction selects which helper diff --git a/tools/testing/selftests/bpf/prog_tests/sockopt_sk.c b/tools/testing/selftests/bpf/prog_tests/sockopt_sk.c index 4b937e5dbaca..164aa5020bf1 100644 --- a/tools/testing/selftests/bpf/prog_tests/sockopt_sk.c +++ b/tools/testing/selftests/bpf/prog_tests/sockopt_sk.c @@ -177,7 +177,7 @@ static int getsetsockopt(void) optlen = sizeof(buf.zc); errno = 0; err = getsockopt(fd, SOL_TCP, TCP_ZEROCOPY_RECEIVE, &buf, &optlen); - if (errno != EPERM) { + if (errno != EINVAL) { log_err("Unexpected getsockopt(TCP_ZEROCOPY_RECEIVE) err=%d errno=%d", err, errno); goto err; diff --git a/tools/testing/selftests/bpf/progs/sockopt_sk.c b/tools/testing/selftests/bpf/progs/sockopt_sk.c index 79c8139b63b8..d0298dccedcd 100644 --- a/tools/testing/selftests/bpf/progs/sockopt_sk.c +++ b/tools/testing/selftests/bpf/progs/sockopt_sk.c @@ -73,17 +73,17 @@ int _getsockopt(struct bpf_sockopt *ctx) */ if (optval + sizeof(struct tcp_zerocopy_receive) > optval_end) - return 0; /* EPERM, bounds check */ + return 0; /* bounds check */ if (((struct tcp_zerocopy_receive *)optval)->address != 0) - return 0; /* EPERM, unexpected data */ + return 0; /* unexpected data */ return 1; } if (ctx->level == SOL_IP && ctx->optname == IP_FREEBIND) { if (optval + 1 > optval_end) - return 0; /* EPERM, bounds check */ + return 0; /* bounds check */ ctx->retval = 0; /* Reset system call return value to zero */ @@ -96,24 +96,24 @@ int _getsockopt(struct bpf_sockopt *ctx) * bytes of data. */ if (optval_end - optval != page_size) - return 0; /* EPERM, unexpected data size */ + return 0; /* unexpected data size */ return 1; } if (ctx->level != SOL_CUSTOM) - return 0; /* EPERM, deny everything except custom level */ + return 0; /* deny everything except custom level */ if (optval + 1 > optval_end) - return 0; /* EPERM, bounds check */ + return 0; /* bounds check */ storage = bpf_sk_storage_get(&socket_storage_map, ctx->sk, 0, BPF_SK_STORAGE_GET_F_CREATE); if (!storage) - return 0; /* EPERM, couldn't get sk storage */ + return 0; /* couldn't get sk storage */ if (!ctx->retval) - return 0; /* EPERM, kernel should not have handled + return 0; /* kernel should not have handled * SOL_CUSTOM, something is wrong! */ ctx->retval = 0; /* Reset system call return value to zero */ @@ -152,7 +152,7 @@ int _setsockopt(struct bpf_sockopt *ctx) /* Overwrite SO_SNDBUF value */ if (optval + sizeof(__u32) > optval_end) - return 0; /* EPERM, bounds check */ + return 0; /* bounds check */ *(__u32 *)optval = 0x55AA; ctx->optlen = 4; @@ -164,7 +164,7 @@ int _setsockopt(struct bpf_sockopt *ctx) /* Always use cubic */ if (optval + 5 > optval_end) - return 0; /* EPERM, bounds check */ + return 0; /* bounds check */ memcpy(optval, "cubic", 5); ctx->optlen = 5; @@ -175,10 +175,10 @@ int _setsockopt(struct bpf_sockopt *ctx) if (ctx->level == SOL_IP && ctx->optname == IP_FREEBIND) { /* Original optlen is larger than PAGE_SIZE. */ if (ctx->optlen != page_size * 2) - return 0; /* EPERM, unexpected data size */ + return 0; /* unexpected data size */ if (optval + 1 > optval_end) - return 0; /* EPERM, bounds check */ + return 0; /* bounds check */ /* Make sure we can trim the buffer. */ optval[0] = 0; @@ -189,21 +189,21 @@ int _setsockopt(struct bpf_sockopt *ctx) * bytes of data. */ if (optval_end - optval != page_size) - return 0; /* EPERM, unexpected data size */ + return 0; /* unexpected data size */ return 1; } if (ctx->level != SOL_CUSTOM) - return 0; /* EPERM, deny everything except custom level */ + return 0; /* deny everything except custom level */ if (optval + 1 > optval_end) - return 0; /* EPERM, bounds check */ + return 0; /* bounds check */ storage = bpf_sk_storage_get(&socket_storage_map, ctx->sk, 0, BPF_SK_STORAGE_GET_F_CREATE); if (!storage) - return 0; /* EPERM, couldn't get sk storage */ + return 0; /* couldn't get sk storage */ storage->val = optval[0]; ctx->optlen = -1; /* BPF has consumed this option, don't call kernel