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 X-Spam-Level: X-Spam-Status: No, score=-25.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 18B76C388F2 for ; Tue, 3 Nov 2020 04:10:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BCB2622277 for ; Tue, 3 Nov 2020 04:10:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="pxCPzGUT" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725980AbgKCEKM (ORCPT ); Mon, 2 Nov 2020 23:10:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35638 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725940AbgKCEKM (ORCPT ); Mon, 2 Nov 2020 23:10:12 -0500 Received: from mail-qv1-xf4a.google.com (mail-qv1-xf4a.google.com [IPv6:2607:f8b0:4864:20::f4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EC101C0617A6 for ; Mon, 2 Nov 2020 20:10:11 -0800 (PST) Received: by mail-qv1-xf4a.google.com with SMTP id x34so9548916qvx.7 for ; Mon, 02 Nov 2020 20:10:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:in-reply-to:message-id:mime-version:references:subject :from:to:cc; bh=pxTIdVkSiwy0DW0JwGKVWppwQt2XT4H9j3x0aB9cgOs=; b=pxCPzGUTk9E0jl11FYJ5iivu7t8FZ1qBza2Mub+UWd5WP1q3snOuwz0zC2fgbZUNoU WQGkGXY7++7B6TWQBiQsfSt2PaYh8IG9sPJW6j4RSxytY9dRilPSNSR0Qov3P9Ga3eoR pAqbj7mPVLACUpIvzdYu0VAKmgNzdrxg9nyG8+vZb+LKZJNQsLo1WRgZvhSA8Tgi9qeY c/m8JYa4VFoRY4bxxIM6leKhLoJit9JBpZXlXyyxJbOxd1HnbKYBEPEzj21ER7gygLnr jANBhO8MzDt284x4dYMkEBThm2rXckC2BrLg759sf5gpmgeGpJ5WjZBGZD1cSBxPSjfd UV8Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=pxTIdVkSiwy0DW0JwGKVWppwQt2XT4H9j3x0aB9cgOs=; b=Kt8fXZBfW01/qUNiemg2Pwm/tAdBINvu9zeheQU4ay9ZnNcKYnlpt+eyez44qhy3em ZJ+0WaoeUjvuurht27+xi61lNtiJmopkZtzqlyusr0Jp+sXA34A5W8AK1DRrvpK+5AKL xjpTjSZbozG64dyeGuWau0xtPCDwPBEoUCNUlEbzM07Mt6Ygq6rYILskFjkZJ5+jvK+r uLSRMD+zs13Sa5uBQSuOnscLo+gdDawiHN7PIjHRigrismaNZTynxOWOV+8p+KXTacgH RVMkBGwZ2LQNiFZ40IkyAcpAiH0SxBNBi8eD2HRlmW4S8ga/t8Z3Zlv1on16/PKjnq7X DocQ== X-Gm-Message-State: AOAM533B+LkrzLawnn23k83x7DtMm5nBZmJ7VSfTf2nyu/cxKqlNE0Ge FND6kD43bYmWQBRndFiCgAPhKV0= X-Google-Smtp-Source: ABdhPJwyAyipL+HC38PCFLuHDNhD7vRkpgNp+y+ZJT7Q/IPjeQDGpnajlCcuM1trpDJCKlAqLZnkzn0= Sender: "pcc via sendgmr" X-Received: from pcc-desktop.svl.corp.google.com ([2620:15c:2ce:0:7220:84ff:fe09:385a]) (user=pcc job=sendgmr) by 2002:ad4:4e84:: with SMTP id dy4mr13013702qvb.47.1604376611105; Mon, 02 Nov 2020 20:10:11 -0800 (PST) Date: Mon, 2 Nov 2020 20:09:40 -0800 In-Reply-To: Message-Id: <8997d900debfcb424dbe721fc2ccaa102560c286.1604376407.git.pcc@google.com> Mime-Version: 1.0 References: X-Mailer: git-send-email 2.29.1.341.ge80a0c044ae-goog Subject: [PATCH v13 4/8] signal: clear non-uapi flag bits when passing/returning sa_flags From: Peter Collingbourne To: Catalin Marinas , Evgenii Stepanov , Kostya Serebryany , Vincenzo Frascino , Dave Martin , Will Deacon , Oleg Nesterov , "Eric W. Biederman" , "James E.J. Bottomley" Cc: Peter Collingbourne , Linux ARM , Kevin Brodsky , Andrey Konovalov , Richard Henderson , linux-api@vger.kernel.org, Helge Deller , David Spickett Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org Previously we were not clearing non-uapi flag bits in sigaction.sa_flags when storing the userspace-provided sa_flags or when returning them via oldact. Start doing so. This allows userspace to detect missing support for flag bits and allows the kernel to use non-uapi bits internally, as we are already doing in arch/x86 for two flag bits. Now that this change is in place, we no longer need the code in arch/x86 that was hiding these bits from userspace, so remove it. This is technically a userspace-visible behavior change for sigaction, as the unknown bits returned via oldact.sa_flags are no longer set. However, we are free to define the behavior for unknown bits exactly because their behavior is currently undefined, so for now we can define the meaning of each of them to be "clear the bit in oldact.sa_flags unless the bit becomes known in the future". Furthermore, this behavior is consistent with OpenBSD [1], illumos [2] and XNU [3] (FreeBSD [4] and NetBSD [5] fail the syscall if unknown bits are set). So there is some precedent for this behavior in other kernels, and in particular in XNU, which is probably the most popular kernel among those that I looked at, which means that this change is less likely to be a compatibility issue. Link: [1] https://github.com/openbsd/src/blob/f634a6a4b5bf832e9c1de77f7894ae2625e74484/sys/kern/kern_sig.c#L278 Link: [2] https://github.com/illumos/illumos-gate/blob/76f19f5fdc974fe5be5c82a556e43a4df93f1de1/usr/src/uts/common/syscall/sigaction.c#L86 Link: [3] https://github.com/apple/darwin-xnu/blob/a449c6a3b8014d9406c2ddbdc81795da24aa7443/bsd/kern/kern_sig.c#L480 Link: [4] https://github.com/freebsd/freebsd/blob/eded70c37057857c6e23fae51f86b8f8f43cd2d0/sys/kern/kern_sig.c#L699 Link: [5] https://github.com/NetBSD/src/blob/3365779becdcedfca206091a645a0e8e22b2946e/sys/kern/sys_sig.c#L473 Signed-off-by: Peter Collingbourne Reviewed-by: Dave Martin Link: https://linux-review.googlesource.com/id/I35aab6f5be932505d90f3b3450c083b4db1eca86 --- v10: - rename SA_UAPI_FLAGS -> UAPI_SA_FLAGS - refactor how we define it to avoid mentioning flags more than once arch/arm/include/asm/signal.h | 2 ++ arch/parisc/include/asm/signal.h | 2 ++ arch/x86/kernel/signal_compat.c | 7 ------- include/linux/signal_types.h | 12 ++++++++++++ kernel/signal.c | 10 ++++++++++ 5 files changed, 26 insertions(+), 7 deletions(-) diff --git a/arch/arm/include/asm/signal.h b/arch/arm/include/asm/signal.h index 65530a042009..430be7774402 100644 --- a/arch/arm/include/asm/signal.h +++ b/arch/arm/include/asm/signal.h @@ -17,6 +17,8 @@ typedef struct { unsigned long sig[_NSIG_WORDS]; } sigset_t; +#define __ARCH_UAPI_SA_FLAGS (SA_THIRTYTWO | SA_RESTORER) + #define __ARCH_HAS_SA_RESTORER #include diff --git a/arch/parisc/include/asm/signal.h b/arch/parisc/include/asm/signal.h index 715c96ba2ec8..30dd1e43ef88 100644 --- a/arch/parisc/include/asm/signal.h +++ b/arch/parisc/include/asm/signal.h @@ -21,6 +21,8 @@ typedef struct { unsigned long sig[_NSIG_WORDS]; } sigset_t; +#define __ARCH_UAPI_SA_FLAGS _SA_SIGGFAULT + #include #endif /* !__ASSEMBLY */ diff --git a/arch/x86/kernel/signal_compat.c b/arch/x86/kernel/signal_compat.c index a7f3e12cfbdb..ddfd919be46c 100644 --- a/arch/x86/kernel/signal_compat.c +++ b/arch/x86/kernel/signal_compat.c @@ -165,16 +165,9 @@ void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact) { signal_compat_build_tests(); - /* Don't leak in-kernel non-uapi flags to user-space */ - if (oact) - oact->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI); - if (!act) return; - /* Don't let flags to be set from userspace */ - act->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI); - if (in_ia32_syscall()) act->sa.sa_flags |= SA_IA32_ABI; if (in_x32_syscall()) diff --git a/include/linux/signal_types.h b/include/linux/signal_types.h index f8a90ae9c6ec..a7887ad84d36 100644 --- a/include/linux/signal_types.h +++ b/include/linux/signal_types.h @@ -68,4 +68,16 @@ struct ksignal { int sig; }; +#ifndef __ARCH_UAPI_SA_FLAGS +#ifdef SA_RESTORER +#define __ARCH_UAPI_SA_FLAGS SA_RESTORER +#else +#define __ARCH_UAPI_SA_FLAGS 0 +#endif +#endif + +#define UAPI_SA_FLAGS \ + (SA_NOCLDSTOP | SA_NOCLDWAIT | SA_SIGINFO | SA_ONSTACK | SA_RESTART | \ + SA_NODEFER | SA_RESETHAND | __ARCH_UAPI_SA_FLAGS) + #endif /* _LINUX_SIGNAL_TYPES_H */ diff --git a/kernel/signal.c b/kernel/signal.c index ef8f2a28d37c..8f5bd12ee41b 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -3985,6 +3985,16 @@ int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact) if (oact) *oact = *k; + /* + * Clear unknown flag bits in order to allow userspace to detect missing + * support for flag bits and to allow the kernel to use non-uapi bits + * internally. + */ + if (act) + act->sa.sa_flags &= UAPI_SA_FLAGS; + if (oact) + oact->sa.sa_flags &= UAPI_SA_FLAGS; + sigaction_compat_abi(act, oact); if (act) { -- 2.29.1.341.ge80a0c044ae-goog