From mboxrd@z Thu Jan 1 00:00:00 1970 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 5DB78EB64DC for ; Tue, 18 Jul 2023 21:01:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230356AbjGRVBC (ORCPT ); Tue, 18 Jul 2023 17:01:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57590 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230057AbjGRVBA (ORCPT ); Tue, 18 Jul 2023 17:01:00 -0400 Received: from mail-pg1-x544.google.com (mail-pg1-x544.google.com [IPv6:2607:f8b0:4864:20::544]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 02794198C for ; Tue, 18 Jul 2023 14:00:59 -0700 (PDT) Received: by mail-pg1-x544.google.com with SMTP id 41be03b00d2f7-55b1238a013so4723995a12.3 for ; Tue, 18 Jul 2023 14:00:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1689714058; x=1692306058; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=OHHcOhkbsv1p/qZwif2W/kSpl8RMjgRTDPZDHV7WrBw=; b=LOkbMmif5Ycr4XzhJft2CzhA9qbAeEjYa/Cr0ll2csDNgcvG/NXmoNZXISITQglpRj hhtX/VRxsa2hxIDKzNTyFAN++h5tdTzFUqqtIFcjQIHCj6Qq2zobuQLE/fBu/qw4+9uq KRjCEp33u2nXN0u+0H1XJGVL6NqeU3WZrWgnYRV3gc0ZAxp803ROYs0SKZ2VXffz8JLE xc97gI3pIYHq4XW72UVvcf3uVT8pn43z6plpgB5LFvwKGuee6miTf9TRMpipJglmdmAd RnU2XIrpwa1voPrQqUppPno9Bpmwtr7nz3oimKRWZIhB/dFSrlBzrIcfo+GK8654aZ4b FLgQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689714058; x=1692306058; 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=OHHcOhkbsv1p/qZwif2W/kSpl8RMjgRTDPZDHV7WrBw=; b=jQD0nw6mRZiXqZOK0ibrdJPEqXrCkhiaV8mwH532Mkaq3MHvL3FQ/lLyCQhuApTEIF oFcvgoRrmUcjtcEQYN4mAvp1mwutDyByXn4iU53B4Fl9tuNvEAoSgPJshfFANVLkQpYC ytccMHktRcVp3cg66jsVp+41DKA7lhU1nNA0oW3f3NllsdF37nSMWDuC9PoRGFiN8NwY 1c54njz436wb/xkrnvz7AKrboH/YB03v7EsrwFlLnXUn1F8jC4TPrHB1HYOscK7lHSps tVuBBx/yIva9qimaOKGYBtRgVf2NzY/cmcVLdeoU/2/ctSeEN+yR+K7UgR0NtI/ljoGU cteQ== X-Gm-Message-State: ABy/qLZ9FUF84mIyKom/mBnGQJXJC356iB7TMVvQJSt/GD+R/Q/S6ECN vzabJOCCwqRLu+9VdAyFpfU= X-Google-Smtp-Source: APBJJlGtYn6KzK28oMCE0qYWdPXLgvr+4ng4J+CyxMR+FL2Vlo5llyfi1/hx5fY2V82w7q/P8bwraA== X-Received: by 2002:a17:90b:788:b0:264:2e2:7be8 with SMTP id l8-20020a17090b078800b0026402e27be8mr13566948pjz.18.1689714058379; Tue, 18 Jul 2023 14:00:58 -0700 (PDT) Received: from localhost ([212.107.28.53]) by smtp.gmail.com with ESMTPSA id 14-20020a17090a0cce00b00262e5449dbcsm20590pjt.24.2023.07.18.14.00.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Jul 2023 14:00:58 -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 v3] riscv: entry: set a0 = -ENOSYS only when syscall != -1 Date: Wed, 19 Jul 2023 04:57:30 +0800 Message-ID: <20230718210037.250665-1-CoelacanthusHex@gmail.com> X-Mailer: git-send-email 2.41.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 commit 9c2598d43510 ("riscv: entry: Save a0 prior syscall_enter_from_user_mode()"). After analysing code, we think that regs->a0 = -ENOSYS should only be executed when syscall != -1 In __seccomp_filter, when seccomp rejected this syscall with specified errno, they will set a0 to return number as syscall ABI, and then return -1. This return number is finally pass 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 = -ENOSYS is always executed. 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 --- v2 -> v3: use if-statement instead of set default value, clarify the type of syscall v1 -> v2: added explanation on why always got ENOSYS arch/riscv/kernel/traps.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index f910dfccbf5d2..5cef728745420 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -297,6 +297,10 @@ asmlinkage __visible __trap_section void do_trap_break(struct pt_regs *regs) asmlinkage __visible __trap_section void do_trap_ecall_u(struct pt_regs *regs) { if (user_mode(regs)) { + /* + * Convert negative numbers to very high and thus out of range + * numbers for comparisons. + */ ulong syscall = regs->a7; regs->epc += 4; @@ -308,7 +312,7 @@ asmlinkage __visible __trap_section void do_trap_ecall_u(struct pt_regs *regs) if (syscall < NR_syscalls) syscall_handler(regs, syscall); - else + else if ((long)syscall != -1L) regs->a0 = -ENOSYS; syscall_exit_to_user_mode(regs); -- 2.41.0