From patchwork Mon Aug 21 19:33:10 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dave Marchevsky X-Patchwork-Id: 13359763 X-Patchwork-Delegate: bpf@iogearbox.net Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 98ACD5684 for ; Mon, 21 Aug 2023 19:33:51 +0000 (UTC) Received: from mx0b-00082601.pphosted.com (mx0b-00082601.pphosted.com [67.231.153.30]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DAB26C2 for ; Mon, 21 Aug 2023 12:33:49 -0700 (PDT) Received: from pps.filterd (m0109332.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 37LIGZZm019809 for ; Mon, 21 Aug 2023 12:33:49 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding : content-type; s=facebook; bh=DwsDN6UHcpH82vQi2k2Ud79uc+Qclz+APkHqCE98Ix4=; b=VtvICIErYnKHhAJXboQfJUIA3eIjqlNtc7TcSsdpR+1+ZlSCxfslNwuC2/PPvaav14yk urx9HOpU9CSHMrw3yo3HUSdQOPQutW5wBJspqw/HO2UFqKfUxEz2SdPQ8SDTp4aBmzSW 1sN3Mdb3CNMdmxT9YixcPGLWyznpA8fVp6o= Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com (PPS) with ESMTPS id 3sjug3es0b-10 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Mon, 21 Aug 2023 12:33:49 -0700 Received: from twshared29562.14.frc2.facebook.com (2620:10d:c085:208::f) by mail.thefacebook.com (2620:10d:c085:21d::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.23; Mon, 21 Aug 2023 12:33:25 -0700 Received: by devbig077.ldc1.facebook.com (Postfix, from userid 158236) id B8A78230241CB; Mon, 21 Aug 2023 12:33:21 -0700 (PDT) From: Dave Marchevsky To: CC: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Kernel Team , , Dave Marchevsky Subject: [PATCH v2 bpf-next 6/7] bpf: Allow bpf_spin_{lock,unlock} in sleepable progs Date: Mon, 21 Aug 2023 12:33:10 -0700 Message-ID: <20230821193311.3290257-7-davemarchevsky@fb.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230821193311.3290257-1-davemarchevsky@fb.com> References: <20230821193311.3290257-1-davemarchevsky@fb.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-GUID: SN2ZLn1Z3ADftKnQY2PlasEzGsdJhi_n X-Proofpoint-ORIG-GUID: SN2ZLn1Z3ADftKnQY2PlasEzGsdJhi_n X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.267,Aquarius:18.0.957,Hydra:6.0.601,FMLib:17.11.176.26 definitions=2023-08-21_08,2023-08-18_01,2023-05-22_02 X-Spam-Status: No, score=-1.7 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, RCVD_IN_DNSWL_BLOCKED,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL, SPF_HELO_NONE,SPF_NONE autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: bpf@iogearbox.net Commit 9e7a4d9831e8 ("bpf: Allow LSM programs to use bpf spin locks") disabled bpf_spin_lock usage in sleepable progs, stating: Sleepable LSM programs can be preempted which means that allowng spin locks will need more work (disabling preemption and the verifier ensuring that no sleepable helpers are called when a spin lock is held). This patch disables preemption before grabbing bpf_spin_lock. The second requirement above "no sleepable helpers are called when a spin lock is held" is implicitly enforced by current verifier logic due to helper calls in spin_lock CS being disabled except for a few exceptions, none of which sleep. Due to above preemption changes, bpf_spin_lock CS can also be considered a RCU CS, so verifier's in_rcu_cs check is modified to account for this. Signed-off-by: Dave Marchevsky --- kernel/bpf/helpers.c | 2 ++ kernel/bpf/verifier.c | 9 +++------ 2 files changed, 5 insertions(+), 6 deletions(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 945a85e25ac5..8bd3812fb8df 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -286,6 +286,7 @@ static inline void __bpf_spin_lock(struct bpf_spin_lock *lock) compiletime_assert(u.val == 0, "__ARCH_SPIN_LOCK_UNLOCKED not 0"); BUILD_BUG_ON(sizeof(*l) != sizeof(__u32)); BUILD_BUG_ON(sizeof(*lock) != sizeof(__u32)); + preempt_disable(); arch_spin_lock(l); } @@ -294,6 +295,7 @@ static inline void __bpf_spin_unlock(struct bpf_spin_lock *lock) arch_spinlock_t *l = (void *)lock; arch_spin_unlock(l); + preempt_enable(); } #else diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 55607ab30522..33e4b854d2d4 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5062,7 +5062,9 @@ static int map_kptr_match_type(struct bpf_verifier_env *env, */ static bool in_rcu_cs(struct bpf_verifier_env *env) { - return env->cur_state->active_rcu_lock || !env->prog->aux->sleepable; + return env->cur_state->active_rcu_lock || + env->cur_state->active_lock.ptr || + !env->prog->aux->sleepable; } /* Once GCC supports btf_type_tag the following mechanism will be replaced with tag check */ @@ -16980,11 +16982,6 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env, verbose(env, "tracing progs cannot use bpf_spin_lock yet\n"); return -EINVAL; } - - if (prog->aux->sleepable) { - verbose(env, "sleepable progs cannot use bpf_spin_lock yet\n"); - return -EINVAL; - } } if (btf_record_has_field(map->record, BPF_TIMER)) {