From mboxrd@z Thu Jan 1 00:00:00 1970 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 BFF8A7E1 for ; Fri, 3 Nov 2023 00:08:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=none Received: from mx0b-00082601.pphosted.com (mx0b-00082601.pphosted.com [67.231.153.30]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5907D136 for ; Thu, 2 Nov 2023 17:08:41 -0700 (PDT) Received: from pps.filterd (m0109331.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 3A2MZgpp016148 for ; Thu, 2 Nov 2023 17:08:40 -0700 Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com (PPS) with ESMTPS id 3u4mprrc07-4 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Thu, 02 Nov 2023 17:08:40 -0700 Received: from twshared58712.02.prn6.facebook.com (2620:10d:c085:108::8) 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 15.1.2507.34; Thu, 2 Nov 2023 17:08:35 -0700 Received: by devbig019.vll3.facebook.com (Postfix, from userid 137359) id 7A7913AD8A6E2; Thu, 2 Nov 2023 17:08:27 -0700 (PDT) From: Andrii Nakryiko To: , , , CC: , Subject: [PATCH bpf-next 02/13] bpf: generalize is_scalar_branch_taken() logic Date: Thu, 2 Nov 2023 17:08:11 -0700 Message-ID: <20231103000822.2509815-3-andrii@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231103000822.2509815-1-andrii@kernel.org> References: <20231103000822.2509815-1-andrii@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-GUID: pwl0idHCp4EiG92Xik5IvpKkzHnJlDkK X-Proofpoint-ORIG-GUID: pwl0idHCp4EiG92Xik5IvpKkzHnJlDkK X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.987,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-11-02_10,2023-11-02_03,2023-05-22_02 Generalize is_branch_taken logic for SCALAR_VALUE register to handle cases when both registers are not constants. Previously supported vs cases are a natural subset of more generic vs set of cases. Generalized logic relies on straightforward segment intersection checks. Signed-off-by: Andrii Nakryiko --- kernel/bpf/verifier.c | 103 ++++++++++++++++++++++++++---------------- 1 file changed, 63 insertions(+), 40 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 52934080042c..2627461164ed 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -14187,82 +14187,104 @@ static int is_scalar_branch_taken(struct bpf_r= eg_state *reg1, struct bpf_reg_sta u8 opcode, bool is_jmp32) { struct tnum t1 =3D is_jmp32 ? tnum_subreg(reg1->var_off) : reg1->var_of= f; + struct tnum t2 =3D is_jmp32 ? tnum_subreg(reg2->var_off) : reg2->var_of= f; u64 umin1 =3D is_jmp32 ? (u64)reg1->u32_min_value : reg1->umin_value; u64 umax1 =3D is_jmp32 ? (u64)reg1->u32_max_value : reg1->umax_value; s64 smin1 =3D is_jmp32 ? (s64)reg1->s32_min_value : reg1->smin_value; s64 smax1 =3D is_jmp32 ? (s64)reg1->s32_max_value : reg1->smax_value; - u64 uval =3D is_jmp32 ? (u32)tnum_subreg(reg2->var_off).value : reg2->v= ar_off.value; - s64 sval =3D is_jmp32 ? (s32)uval : (s64)uval; + u64 umin2 =3D is_jmp32 ? (u64)reg2->u32_min_value : reg2->umin_value; + u64 umax2 =3D is_jmp32 ? (u64)reg2->u32_max_value : reg2->umax_value; + s64 smin2 =3D is_jmp32 ? (s64)reg2->s32_min_value : reg2->smin_value; + s64 smax2 =3D is_jmp32 ? (s64)reg2->s32_max_value : reg2->smax_value; =20 switch (opcode) { case BPF_JEQ: - if (tnum_is_const(t1)) - return !!tnum_equals_const(t1, uval); - else if (uval < umin1 || uval > umax1) + /* constants, umin/umax and smin/smax checks would be + * redundant in this case because they all should match + */ + if (tnum_is_const(t1) && tnum_is_const(t2)) + return t1.value =3D=3D t2.value; + /* const ranges */ + if (umin1 =3D=3D umax1 && umin2 =3D=3D umax2) + return umin1 =3D=3D umin2; + if (smin1 =3D=3D smax1 && smin2 =3D=3D smax2) + return smin1 =3D=3D smin2; + /* non-overlapping ranges */ + if (umin1 > umax2 || umax1 < umin2) return 0; - else if (sval < smin1 || sval > smax1) + if (smin1 > smax2 || smax1 < smin2) return 0; break; case BPF_JNE: - if (tnum_is_const(t1)) - return !tnum_equals_const(t1, uval); - else if (uval < umin1 || uval > umax1) + /* constants, umin/umax and smin/smax checks would be + * redundant in this case because they all should match + */ + if (tnum_is_const(t1) && tnum_is_const(t2)) + return t1.value !=3D t2.value; + /* non-overlapping ranges */ + if (umin1 > umax2 || umax1 < umin2) return 1; - else if (sval < smin1 || sval > smax1) + if (smin1 > smax2 || smax1 < smin2) return 1; break; case BPF_JSET: - if ((~t1.mask & t1.value) & uval) + if (!is_reg_const(reg2, is_jmp32)) { + swap(reg1, reg2); + swap(t1, t2); + } + if (!is_reg_const(reg2, is_jmp32)) + return -1; + if ((~t1.mask & t1.value) & t2.value) return 1; - if (!((t1.mask | t1.value) & uval)) + if (!((t1.mask | t1.value) & t2.value)) return 0; break; case BPF_JGT: - if (umin1 > uval ) + if (umin1 > umax2) return 1; - else if (umax1 <=3D uval) + else if (umax1 <=3D umin2) return 0; break; case BPF_JSGT: - if (smin1 > sval) + if (smin1 > smax2) return 1; - else if (smax1 <=3D sval) + else if (smax1 <=3D smin2) return 0; break; case BPF_JLT: - if (umax1 < uval) + if (umax1 < umin2) return 1; - else if (umin1 >=3D uval) + else if (umin1 >=3D umax2) return 0; break; case BPF_JSLT: - if (smax1 < sval) + if (smax1 < smin2) return 1; - else if (smin1 >=3D sval) + else if (smin1 >=3D smax2) return 0; break; case BPF_JGE: - if (umin1 >=3D uval) + if (umin1 >=3D umax2) return 1; - else if (umax1 < uval) + else if (umax1 < umin2) return 0; break; case BPF_JSGE: - if (smin1 >=3D sval) + if (smin1 >=3D smax2) return 1; - else if (smax1 < sval) + else if (smax1 < smin2) return 0; break; case BPF_JLE: - if (umax1 <=3D uval) + if (umax1 <=3D umin2) return 1; - else if (umin1 > uval) + else if (umin1 > umax2) return 0; break; case BPF_JSLE: - if (smax1 <=3D sval) + if (smax1 <=3D smin2) return 1; - else if (smin1 > sval) + else if (smin1 > smax2) return 0; break; } @@ -14341,28 +14363,28 @@ static int is_pkt_ptr_branch_taken(struct bpf_r= eg_state *dst_reg, static int is_branch_taken(struct bpf_reg_state *reg1, struct bpf_reg_st= ate *reg2, u8 opcode, bool is_jmp32) { - u64 val; - if (reg_is_pkt_pointer_any(reg1) && reg_is_pkt_pointer_any(reg2) && !is= _jmp32) return is_pkt_ptr_branch_taken(reg1, reg2, opcode); =20 - /* try to make sure reg2 is a constant SCALAR_VALUE */ - if (!is_reg_const(reg2, is_jmp32)) { - opcode =3D flip_opcode(opcode); - swap(reg1, reg2); - } - /* for now we expect reg2 to be a constant to make any useful decisions= */ - if (!is_reg_const(reg2, is_jmp32)) - return -1; - val =3D reg_const_value(reg2, is_jmp32); + if (__is_pointer_value(false, reg1) || __is_pointer_value(false, reg2))= { + u64 val; + + /* arrange that reg2 is a scalar, and reg1 is a pointer */ + if (!is_reg_const(reg2, is_jmp32)) { + opcode =3D flip_opcode(opcode); + swap(reg1, reg2); + } + /* and ensure that reg2 is a constant */ + if (!is_reg_const(reg2, is_jmp32)) + return -1; =20 - if (__is_pointer_value(false, reg1)) { if (!reg_not_null(reg1)) return -1; =20 /* If pointer is valid tests against zero will fail so we can * use this to direct branch taken. */ + val =3D reg_const_value(reg2, is_jmp32); if (val !=3D 0) return -1; =20 @@ -14376,6 +14398,7 @@ static int is_branch_taken(struct bpf_reg_state *= reg1, struct bpf_reg_state *reg } } =20 + /* now deal with two scalars, but not necessarily constants */ return is_scalar_branch_taken(reg1, reg2, opcode, is_jmp32); } =20 --=20 2.34.1