From nobody Sun Feb 8 03:27:38 2026 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 E9CB4EB64DC for ; Tue, 18 Jul 2023 16:29:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232335AbjGRQ3q (ORCPT ); Tue, 18 Jul 2023 12:29:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43460 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231302AbjGRQ3p (ORCPT ); Tue, 18 Jul 2023 12:29:45 -0400 Received: from mail-pf1-x441.google.com (mail-pf1-x441.google.com [IPv6:2607:f8b0:4864:20::441]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 45D53E77 for ; Tue, 18 Jul 2023 09:29:44 -0700 (PDT) Received: by mail-pf1-x441.google.com with SMTP id d2e1a72fcca58-66872d4a141so3856410b3a.1 for ; Tue, 18 Jul 2023 09:29:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1689697784; x=1692289784; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=yeYxjLuTkeXplzaU1/5MYQdHyT2ovErfxDS2RgTO3Ok=; b=gLQjkG4fVekO4wKfOEhQiTxp/MrdgHIZnXQ0WmW0vwH325FTQMH+hvO0Pl6Tv4So7B TCAB08k/nZ6tFUTBDeGsVNR9mEAipRHe0EIzaEVBs6wXYt6zGOPX28c+scik8leIgk07 eXHW9moGIYwa1vSPSLZqXjFacnO4ukAE8io9e5ttRdydgXuNH2kjH/YQyI45Esm893uf GJnWKDfoIhvCgOP1jZL1yqtNK5n1DzSHjkMwGIunf7HYrnEdIAjkNt8C4/cbrV6ZnN1G J1XVF3sCTJ/XkxODVioUM9fy0W9h0Uo/IwsR9bTOhOMXUXsIx2qEzGpePAVqsxehokRB WS9Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689697784; x=1692289784; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=yeYxjLuTkeXplzaU1/5MYQdHyT2ovErfxDS2RgTO3Ok=; b=DoUNpdVxLFk+stzFrMJ6SbNA2SjLPTexSwqCWxH5OzClhQcGrwVpIi+JiF/A75u2jh XWu9HCA1/7/29SB3JClIa2ddCbtraQbR4Zzxjwu2VT7kRrsJZqfdvLCLKZ9w+Di6UBtm eCgrCrtgrtwAXdEuU2+KfuHErc9BKpbz17cSwk1XRrhU2em/rv2awSPFQYOBuac6MhB3 9jfE9yf18R31E5QDuBDo166RN11ibAgUP+USjjpTXX6uVqcFx5aZEXucHi3VtD1YiigI RybqWvhFU95cwjW4kNqLGj+xC4gD6wTx4sorFMzCBpEdJ5s9v3PHeeLesRzG/+dChLP8 bxvA== X-Gm-Message-State: ABy/qLazJfbRMDVDeA/qeag5uPA1xPZ2ElWwo8iUov5MEPsYihA4AfWy V8zJP1w3ktV5hlrzCxV0eDI= X-Google-Smtp-Source: APBJJlHJ1Qy7cPNo88MjFDp9ATIP+Ij4hUgUh/REqcmbOnaMxlELvzKUTeKwAjO70btUmn9wUqG1KA== X-Received: by 2002:a05:6a20:1443:b0:101:1951:d491 with SMTP id a3-20020a056a20144300b001011951d491mr17658741pzi.6.1689697783544; Tue, 18 Jul 2023 09:29:43 -0700 (PDT) Received: from localhost ([212.107.28.53]) by smtp.gmail.com with ESMTPSA id g22-20020a62e316000000b0062bc045bf4fsm1807671pfh.19.2023.07.18.09.29.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Jul 2023 09:29:43 -0700 (PDT) From: Celeste Liu X-Google-Original-From: Celeste Liu To: Palmer Dabbelt , Paul Walmsley , Albert Ou , Guo Ren , =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= , Conor Dooley , linux-riscv@lists.infradead.org Cc: linux-kernel@vger.kernel.org, Celeste Liu , Felix Yan , Ruizhe Pan , Shiqi Zhang Subject: [PATCH v2] riscv: entry: set a0 prior to syscall_enter_from_user_mode Date: Wed, 19 Jul 2023 00:28:46 +0800 Message-ID: <20230718162940.226118-1-CoelacanthusHex@gmail.com> X-Mailer: git-send-email 2.41.0 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When we test seccomp with 6.4 kernel, we found errno has wrong value. If we deny NETLINK_AUDIT with EAFNOSUPPORT, after f0bddf50586d, we will get ENOSYS instead. We got same result with 9c2598d43510 ("riscv: entry: Sa= ve a0 prior syscall_enter_from_user_mode()"). After analysing code, we think that regs->a0 =3D -ENOSYS should be advanced= before syscall_enter_from_user_mode to fix this problem. In __seccomp_filter, when seccomp rejected this syscall with specified errno, they will set a0 to ret= urn number as syscall ABI, and then return -1. This return number is finally pa= ss as return number of syscall_enter_from_user_mode, and then is compared with NR_syscalls after converted to ulong (so it will be ULONG_MAX). The condition syscall < NR_syscalls will always be false, so regs->a0 =3D -= ENOSYS is always executable. It covered a0 set by seccomp, so we always get ENOSYS when match seccomp RET_ERRNO rule. Fixes: f0bddf50586d ("riscv: entry: Convert to generic entry") Reported-by: Felix Yan Co-developed-by: Ruizhe Pan Signed-off-by: Ruizhe Pan Co-developed-by: Shiqi Zhang Signed-off-by: Shiqi Zhang Signed-off-by: Celeste Liu Tested-by: Felix Yan --- v1 -> v2: added explanation on why always got ENOSYS arch/riscv/kernel/traps.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index f910dfccbf5d2..ccadb5ffd063c 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -301,6 +301,7 @@ asmlinkage __visible __trap_section void do_trap_ecall_= u(struct pt_regs *regs) =20 regs->epc +=3D 4; regs->orig_a0 =3D regs->a0; + regs->a0 =3D -ENOSYS; =20 riscv_v_vstate_discard(regs); =20 @@ -308,8 +309,6 @@ asmlinkage __visible __trap_section void do_trap_ecall_= u(struct pt_regs *regs) =20 if (syscall < NR_syscalls) syscall_handler(regs, syscall); - else - regs->a0 =3D -ENOSYS; =20 syscall_exit_to_user_mode(regs); } else { --=20 2.41.0