From patchwork Fri Aug 26 17:29:15 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eduard Zingerman X-Patchwork-Id: 12956352 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 F1E3DECAAD6 for ; Fri, 26 Aug 2022 17:30:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344166AbiHZRaI (ORCPT ); Fri, 26 Aug 2022 13:30:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58944 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234955AbiHZRaG (ORCPT ); Fri, 26 Aug 2022 13:30:06 -0400 Received: from mail-ej1-x629.google.com (mail-ej1-x629.google.com [IPv6:2a00:1450:4864:20::629]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 386107172E for ; Fri, 26 Aug 2022 10:30:04 -0700 (PDT) Received: by mail-ej1-x629.google.com with SMTP id w19so4415335ejc.7 for ; Fri, 26 Aug 2022 10:30:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc; bh=xwWJr3KXk5FI/Lu0S/kdDeP3TU26z9zp15vm0h3W7jE=; b=a2udOxIUU2REKnnC90RBA/FfCj+c+yZrWsTFrXW9fWArUuIQC5qDpHurWDlXuULqB/ K4GL22HUSKpQb6ulJW4f56k0Jti15CEosRWfvRe8voMMucgP2oDEjXGFymHyXHJz5Ap9 /0bhgTSh0CtP9xbGWiic/ThQ+d2VNs/5yGlR5ZhvIw4KqGAie8l0NMK9Ct/XlmBb9nKH 5I5RlNYV9U0VDIi7MYEtPmmBDMTJ9irOX1rmDxLr2btGV5wM45i2qlt03UGX7OchNjk+ pQelV23NgqYUhe2OXrYgQaGAVZSQ+PyjsOIuS92D1jKT07apbxwlZ2r8at0PjNBdo/qS JtTw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc; bh=xwWJr3KXk5FI/Lu0S/kdDeP3TU26z9zp15vm0h3W7jE=; b=nLj+wKuzMMn+7hsAOVqIfaLoChVq53X7jVUsTo70VE8rhj4X/KteHC1Th830ptLkpn jeFTpxUDEMuO7d3y1LF6kxrm5+ACJCqCavmexyWnzTuvaxlQaurXALl/GGqfj/FpmghJ CV2ohvTIzSYG4tazeUm+WwEVlxohOuZ1AuX2XzyRSqHnPHV5v4goqfhEmu5yR2sySSoP f2sY9vjEtNjxa7BwsyhOv8gQ9ol9+EnGTPGAGvCXUvpexAXDLjNxdBOmTfHEuJldfjn7 rZpUYhOcwXn2LwvSnFruE65cJfxrgyBtux21ADjUsxrp9j8f36qaE/0lQpAtir4axcgd qk0Q== X-Gm-Message-State: ACgBeo3ZAVE5T7mMd+ME6pDZQNSHsLzl7FYXoHpbEm3Jf1mTZR94UPEG gAEUkmxvu7PSi2CEgHeiUqI6RJJVMf4GtoUw X-Google-Smtp-Source: AA6agR7kRJ1qpRiq5NRCok68XuaiobRy5C+GxXYTjj4bWrSkQ+AhyQh4FA2ZZbZ+TWzhh2LMlXweDw== X-Received: by 2002:a17:907:9693:b0:73d:cc84:deb with SMTP id hd19-20020a170907969300b0073dcc840debmr6001718ejc.552.1661535002888; Fri, 26 Aug 2022 10:30:02 -0700 (PDT) Received: from badger.. (boundsly.muster.volia.net. [93.72.16.93]) by smtp.gmail.com with ESMTPSA id l13-20020a170906a40d00b0073d79d0c9c7sm1119896ejz.127.2022.08.26.10.30.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Aug 2022 10:30:02 -0700 (PDT) From: Eduard Zingerman To: bpf@vger.kernel.org, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, kernel-team@fb.com, yhs@fb.com, john.fastabend@gmail.com Cc: Eduard Zingerman Subject: [PATCH bpf-next 2/2] selftests/bpf: check nullness propagation for reg to reg comparisons Date: Fri, 26 Aug 2022 20:29:15 +0300 Message-Id: <20220826172915.1536914-3-eddyz87@gmail.com> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220826172915.1536914-1-eddyz87@gmail.com> References: <20220826172915.1536914-1-eddyz87@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net Verify that nullness information is porpagated in the branches of register to register JEQ and JNE operations. Signed-off-by: Eduard Zingerman Acked-by: Yonghong Song --- .../bpf/verifier/jeq_infer_not_null.c | 166 ++++++++++++++++++ 1 file changed, 166 insertions(+) create mode 100644 tools/testing/selftests/bpf/verifier/jeq_infer_not_null.c diff --git a/tools/testing/selftests/bpf/verifier/jeq_infer_not_null.c b/tools/testing/selftests/bpf/verifier/jeq_infer_not_null.c new file mode 100644 index 000000000000..d73f6198d544 --- /dev/null +++ b/tools/testing/selftests/bpf/verifier/jeq_infer_not_null.c @@ -0,0 +1,166 @@ +{ + /* This is equivalent to the following program: + * + * r6 = skb->sk; + * r7 = sk_fullsock(r6); + * r0 = sk_fullsock(r6); + * if (r0 == 0) return 0; (a) + * if (r0 != r7) return 0; (b) + * *r7->type; (c) + * return 0; + * + * It is safe to dereference r7 at point (c), because of (a) and (b). + * The test verifies that relation r0 == r7 is propagated from (b) to (c). + */ + "jne/jeq infer not null, PTR_TO_SOCKET_OR_NULL -> PTR_TO_SOCKET for JNE false branch", + .insns = { + /* r6 = skb->sk; */ + BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, offsetof(struct __sk_buff, sk)), + /* if (r6 == 0) return 0; */ + BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 8), + /* r7 = sk_fullsock(skb); */ + BPF_MOV64_REG(BPF_REG_1, BPF_REG_6), + BPF_EMIT_CALL(BPF_FUNC_sk_fullsock), + BPF_MOV64_REG(BPF_REG_7, BPF_REG_0), + /* r0 = sk_fullsock(skb); */ + BPF_MOV64_REG(BPF_REG_1, BPF_REG_6), + BPF_EMIT_CALL(BPF_FUNC_sk_fullsock), + /* if (r0 == null) return 0; */ + BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2), + /* if (r0 == r7) r0 = *(r7->type); */ + BPF_JMP_REG(BPF_JNE, BPF_REG_0, BPF_REG_7, 1), /* Use ! JNE ! */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_7, offsetof(struct bpf_sock, type)), + /* return 0 */ + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .prog_type = BPF_PROG_TYPE_CGROUP_SKB, + .result = ACCEPT, +}, +{ + /* Same as above, but verify that another branch of JNE still + * prohibits access to PTR_MAYBE_NULL. + */ + "jne/jeq infer not null, PTR_TO_SOCKET_OR_NULL unchanged for JNE true branch", + .insns = { + /* r6 = skb->sk */ + BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, offsetof(struct __sk_buff, sk)), + /* if (r6 == 0) return 0; */ + BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 9), + /* r7 = sk_fullsock(skb); */ + BPF_MOV64_REG(BPF_REG_1, BPF_REG_6), + BPF_EMIT_CALL(BPF_FUNC_sk_fullsock), + BPF_MOV64_REG(BPF_REG_7, BPF_REG_0), + /* r0 = sk_fullsock(skb); */ + BPF_MOV64_REG(BPF_REG_1, BPF_REG_6), + BPF_EMIT_CALL(BPF_FUNC_sk_fullsock), + /* if (r0 == null) return 0; */ + BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 3), + /* if (r0 == r7) return 0; */ + BPF_JMP_REG(BPF_JNE, BPF_REG_0, BPF_REG_7, 1), /* Use ! JNE ! */ + BPF_JMP_IMM(BPF_JA, 0, 0, 1), + /* r0 = *(r7->type); */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_7, offsetof(struct bpf_sock, type)), + /* return 0 */ + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .prog_type = BPF_PROG_TYPE_CGROUP_SKB, + .result = REJECT, + .errstr = "R7 invalid mem access 'sock_or_null'", +}, +{ + /* Same as a first test, but not null should be inferred for JEQ branch */ + "jne/jeq infer not null, PTR_TO_SOCKET_OR_NULL -> PTR_TO_SOCKET for JEQ true branch", + .insns = { + /* r6 = skb->sk; */ + BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, offsetof(struct __sk_buff, sk)), + /* if (r6 == null) return 0; */ + BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 9), + /* r7 = sk_fullsock(skb); */ + BPF_MOV64_REG(BPF_REG_1, BPF_REG_6), + BPF_EMIT_CALL(BPF_FUNC_sk_fullsock), + BPF_MOV64_REG(BPF_REG_7, BPF_REG_0), + /* r0 = sk_fullsock(skb); */ + BPF_MOV64_REG(BPF_REG_1, BPF_REG_6), + BPF_EMIT_CALL(BPF_FUNC_sk_fullsock), + /* if (r0 == null) return 0; */ + BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 3), + /* if (r0 != r7) return 0; */ + BPF_JMP_REG(BPF_JEQ, BPF_REG_0, BPF_REG_7, 1), /* Use ! JEQ ! */ + BPF_JMP_IMM(BPF_JA, 0, 0, 1), + /* r0 = *(r7->type); */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_7, offsetof(struct bpf_sock, type)), + /* return 0; */ + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .prog_type = BPF_PROG_TYPE_CGROUP_SKB, + .result = ACCEPT, +}, +{ + /* Same as above, but verify that another branch of JNE still + * prohibits access to PTR_MAYBE_NULL. + */ + "jne/jeq infer not null, PTR_TO_SOCKET_OR_NULL unchanged for JEQ false branch", + .insns = { + /* r6 = skb->sk; */ + BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, offsetof(struct __sk_buff, sk)), + /* if (r6 == null) return 0; */ + BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 8), + /* r7 = sk_fullsock(skb); */ + BPF_MOV64_REG(BPF_REG_1, BPF_REG_6), + BPF_EMIT_CALL(BPF_FUNC_sk_fullsock), + BPF_MOV64_REG(BPF_REG_7, BPF_REG_0), + /* r0 = sk_fullsock(skb); */ + BPF_MOV64_REG(BPF_REG_1, BPF_REG_6), + BPF_EMIT_CALL(BPF_FUNC_sk_fullsock), + /* if (r0 == null) return 0; */ + BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2), + /* if (r0 != r7) r0 = *(r7->type); */ + BPF_JMP_REG(BPF_JEQ, BPF_REG_0, BPF_REG_7, 1), /* Use ! JEQ ! */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_7, offsetof(struct bpf_sock, type)), + /* return 0; */ + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .prog_type = BPF_PROG_TYPE_CGROUP_SKB, + .result = REJECT, + .errstr = "R7 invalid mem access 'sock_or_null'", +}, +{ + /* Maps are treated in a different branch of `mark_ptr_not_null_reg`, + * so separate test for maps case. + */ + "jne/jeq infer not null, PTR_TO_MAP_VALUE_OR_NULL -> PTR_TO_MAP_VALUE", + .insns = { + /* r9 = &some stack to use as key */ + BPF_ST_MEM(BPF_W, BPF_REG_10, -8, 0), + BPF_MOV64_REG(BPF_REG_9, BPF_REG_10), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_9, -8), + /* r8 = process local map */ + BPF_LD_MAP_FD(BPF_REG_8, 0), + /* r6 = map_lookup_elem(r8, r9); */ + BPF_MOV64_REG(BPF_REG_1, BPF_REG_8), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_9), + BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem), + BPF_MOV64_REG(BPF_REG_6, BPF_REG_0), + /* r7 = map_lookup_elem(r8, r9); */ + BPF_MOV64_REG(BPF_REG_1, BPF_REG_8), + BPF_MOV64_REG(BPF_REG_2, BPF_REG_9), + BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem), + BPF_MOV64_REG(BPF_REG_7, BPF_REG_0), + /* if (r6 == 0) return 0; */ + BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 2), + /* if (r6 != r7) return 0; */ + BPF_JMP_REG(BPF_JNE, BPF_REG_6, BPF_REG_7, 1), + /* read *r7; */ + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_7, offsetof(struct bpf_xdp_sock, queue_id)), + /* return 0; */ + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .fixup_map_xskmap = { 3 }, + .prog_type = BPF_PROG_TYPE_XDP, + .result = ACCEPT, +},