From patchwork Fri Jan 15 21:10:35 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Chang S. Bae" X-Patchwork-Id: 41724 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 2BA72398B15C; Fri, 15 Jan 2021 21:15:21 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 2BA72398B15C DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1610745321; bh=uy3xaJE7jSjibq82ut+JKDvkFL0OfF9SbgAlqfpp4qs=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=W5oLdh/TcHdRo4Wzo484EIL0oBeicn9q27SEsc6IeqziAZuXo6558ESFefhO2TLgY 2wvbEOkVs4OlwT/PDiYQPq+tuvOf/hiertBCSrPifNLzV7g8MQD3itGimrrY+2BkqR aYUKDgqVRCT5Xsp7kTHVeHquAPCc2GcTbUg0IQXs= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by sourceware.org (Postfix) with ESMTPS id 660C13857C69 for ; Fri, 15 Jan 2021 21:15:18 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 660C13857C69 IronPort-SDR: K99S4aJjVVYr81w7Y2TiNvcU2dS+r/39tP5lq2l86QS/gppWUpbrmq+ZYl0oTo3ytasy/Xdbzl g6aPo+3OHRew== X-IronPort-AV: E=McAfee;i="6000,8403,9865"; a="158382273" X-IronPort-AV: E=Sophos;i="5.79,350,1602572400"; d="scan'208";a="158382273" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Jan 2021 13:15:15 -0800 IronPort-SDR: 3PT4bxLfEwP5HFYRICS1ZmmYe5RrrnG2RAY/PQYliJIY8xTBAcwNxG7iynVroW3Xi4Da8uZzAO reIMX9+p27rA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.79,350,1602572400"; d="scan'208";a="401418963" Received: from chang-linux-3.sc.intel.com ([172.25.66.175]) by fmsmga002.fm.intel.com with ESMTP; 15 Jan 2021 13:15:15 -0800 To: bp@suse.de, tglx@linutronix.de, mingo@kernel.org, luto@kernel.org, x86@kernel.org Subject: [PATCH v4 1/4] x86/signal: Introduce helpers to get the maximum signal frame size Date: Fri, 15 Jan 2021 13:10:35 -0800 Message-Id: <20210115211038.2072-2-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210115211038.2072-1-chang.seok.bae@intel.com> References: <20210115211038.2072-1-chang.seok.bae@intel.com> X-Spam-Status: No, score=-10.4 required=5.0 tests=BAYES_00, GIT_PATCH_0, KAM_ASCII_DIVIDERS, KAM_DMARC_STATUS, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: "Chang S. Bae via Libc-alpha" From: "Chang S. Bae" Reply-To: "Chang S. Bae" Cc: linux-arch@vger.kernel.org, len.brown@intel.com, tony.luck@intel.com, libc-alpha@sourceware.org, ravi.v.shankar@intel.com, chang.seok.bae@intel.com, jannh@google.com, linux-kernel@vger.kernel.org, dave.hansen@intel.com, Borislav Petkov , linux-api@vger.kernel.org, Dave.Martin@arm.com Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" Signal frames do not have a fixed format and can vary in size when a number of things change: support XSAVE features, 32 vs. 64-bit apps. Add the code to support a runtime method for userspace to dynamically discover how large a signal stack needs to be. Introduce a new variable, max_frame_size, and helper functions for the calculation to be used in a new user interface. Set max_frame_size to a system-wide worst-case value, instead of storing multiple app-specific values. Signed-off-by: Chang S. Bae Reviewed-by: Len Brown Acked-by: H.J. Lu Cc: Borislav Petkov Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org --- Changes from v2: * Renamed the fpstate size helper with cleanup (Borislav Petkov) * Moved the sigframe struct size defines to where used (Borislav Petkov) * Removed unneeded sentence in the changelog (Borislav Petkov) Change from v1: * Took stack alignment into account for sigframe size (Dave Martin) --- arch/x86/include/asm/fpu/signal.h | 2 ++ arch/x86/include/asm/sigframe.h | 2 ++ arch/x86/kernel/cpu/common.c | 3 ++ arch/x86/kernel/fpu/signal.c | 19 +++++++++++ arch/x86/kernel/signal.c | 57 +++++++++++++++++++++++++++++-- 5 files changed, 81 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/fpu/signal.h b/arch/x86/include/asm/fpu/signal.h index 7fb516b6893a..8b6631dffefd 100644 --- a/arch/x86/include/asm/fpu/signal.h +++ b/arch/x86/include/asm/fpu/signal.h @@ -29,6 +29,8 @@ unsigned long fpu__alloc_mathframe(unsigned long sp, int ia32_frame, unsigned long *buf_fx, unsigned long *size); +unsigned long fpu__get_fpstate_size(void); + extern void fpu__init_prepare_fx_sw_frame(void); #endif /* _ASM_X86_FPU_SIGNAL_H */ diff --git a/arch/x86/include/asm/sigframe.h b/arch/x86/include/asm/sigframe.h index 84eab2724875..5b1ed650b124 100644 --- a/arch/x86/include/asm/sigframe.h +++ b/arch/x86/include/asm/sigframe.h @@ -85,4 +85,6 @@ struct rt_sigframe_x32 { #endif /* CONFIG_X86_64 */ +void __init init_sigframe_size(void); + #endif /* _ASM_X86_SIGFRAME_H */ diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 35ad8480c464..6954932272d5 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -58,6 +58,7 @@ #include #include #include +#include #include "cpu.h" @@ -1331,6 +1332,8 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c) fpu__init_system(c); + init_sigframe_size(); + #ifdef CONFIG_X86_32 /* * Regardless of whether PCID is enumerated, the SDM says diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c index a4ec65317a7f..dbb304e48f16 100644 --- a/arch/x86/kernel/fpu/signal.c +++ b/arch/x86/kernel/fpu/signal.c @@ -507,6 +507,25 @@ fpu__alloc_mathframe(unsigned long sp, int ia32_frame, return sp; } + +unsigned long fpu__get_fpstate_size(void) +{ + unsigned long ret = xstate_sigframe_size(); + + /* + * This space is needed on (most) 32-bit kernels, or when a 32-bit + * app is running on a 64-bit kernel. To keep things simple, just + * assume the worst case and always include space for 'freg_state', + * even for 64-bit apps on 64-bit kernels. This wastes a bit of + * space, but keeps the code simple. + */ + if ((IS_ENABLED(CONFIG_IA32_EMULATION) || + IS_ENABLED(CONFIG_X86_32)) && use_fxsr()) + ret += sizeof(struct fregs_state); + + return ret; +} + /* * Prepare the SW reserved portion of the fxsave memory layout, indicating * the presence of the extended state information in the memory layout diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index be0d7d4152ec..138a9f5b78d8 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -212,6 +212,11 @@ do { \ * Set up a signal frame. */ +/* x86 ABI requires 16-byte alignment */ +#define FRAME_ALIGNMENT 16UL + +#define MAX_FRAME_PADDING (FRAME_ALIGNMENT - 1) + /* * Determine which stack to use.. */ @@ -222,9 +227,9 @@ static unsigned long align_sigframe(unsigned long sp) * Align the stack pointer according to the i386 ABI, * i.e. so that on function entry ((sp + 4) & 15) == 0. */ - sp = ((sp + 4) & -16ul) - 4; + sp = ((sp + 4) & -FRAME_ALIGNMENT) - 4; #else /* !CONFIG_X86_32 */ - sp = round_down(sp, 16) - 8; + sp = round_down(sp, FRAME_ALIGNMENT) - 8; #endif return sp; } @@ -663,6 +668,54 @@ SYSCALL_DEFINE0(rt_sigreturn) return 0; } +/* + * There are four different struct types for signal frame: sigframe_ia32, + * rt_sigframe_ia32, rt_sigframe_x32, and rt_sigframe. Use the worst case + * -- the largest size. It means the size for 64-bit apps is a bit more + * than needed, but this keeps the code simple. + */ +#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION) +# define MAX_FRAME_SIGINFO_UCTXT_SIZE sizeof(struct sigframe_ia32) +#else +# define MAX_FRAME_SIGINFO_UCTXT_SIZE sizeof(struct rt_sigframe) +#endif + +/* + * The FP state frame contains an XSAVE buffer which must be 64-byte aligned. + * If a signal frame starts at an unaligned address, extra space is required. + * This is the max alignment padding, conservatively. + */ +#define MAX_XSAVE_PADDING 63UL + +/* + * The frame data is composed of the following areas and laid out as: + * + * ------------------------- + * | alignment padding | + * ------------------------- + * | (f)xsave frame | + * ------------------------- + * | fsave header | + * ------------------------- + * | alignment padding | + * ------------------------- + * | siginfo + ucontext | + * ------------------------- + */ + +/* max_frame_size tells userspace the worst case signal stack size. */ +static unsigned long __ro_after_init max_frame_size; + +void __init init_sigframe_size(void) +{ + max_frame_size = MAX_FRAME_SIGINFO_UCTXT_SIZE + MAX_FRAME_PADDING; + + max_frame_size += fpu__get_fpstate_size() + MAX_XSAVE_PADDING; + + /* Userspace expects an aligned size. */ + max_frame_size = round_up(max_frame_size, FRAME_ALIGNMENT); +} + static inline int is_ia32_compat_frame(struct ksignal *ksig) { return IS_ENABLED(CONFIG_IA32_EMULATION) && From patchwork Fri Jan 15 21:10:36 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Chang S. Bae" X-Patchwork-Id: 41725 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id B284F398B152; Fri, 15 Jan 2021 21:15:21 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org B284F398B152 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1610745321; bh=E1yEDiY+X77mDbCCxBf51lxlWPhqR2IR5fpTGubnlhQ=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=sX9St8EOYVOF+ZG8+bPk1DajqXpXpQa0WQHpEghYX9KpLmzYms4v7QEp07OwLl1z6 wzbosS1SCvmHfLuAycrJ9PEHAeF6QmxWr+Fst+vihIJJYuheGe9uVCME+1HegE3xNg EBvykenMqcGDw4F0Zkbk6tQryG25NjvJN5FpVhDM= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by sourceware.org (Postfix) with ESMTPS id EF6133987C39 for ; Fri, 15 Jan 2021 21:15:18 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org EF6133987C39 IronPort-SDR: EodVZl4CYMUqA18bD+BPgbZddYzxavr4jCpn7wFwXZaHCW9Bzle5rmuu8w30yO65p7J8u+NFoD nR2D2G4C2urA== X-IronPort-AV: E=McAfee;i="6000,8403,9865"; a="158382274" X-IronPort-AV: E=Sophos;i="5.79,350,1602572400"; d="scan'208";a="158382274" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Jan 2021 13:15:15 -0800 IronPort-SDR: GF4VNj/rfZHCUuhZlfp8BElW8w7/P1PwclGxRzbXTs+r/avtUDf6f38YL9ieSYTOyjmT5/Spxp 6z4zJ92xbbGw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.79,350,1602572400"; d="scan'208";a="401418967" Received: from chang-linux-3.sc.intel.com ([172.25.66.175]) by fmsmga002.fm.intel.com with ESMTP; 15 Jan 2021 13:15:15 -0800 To: bp@suse.de, tglx@linutronix.de, mingo@kernel.org, luto@kernel.org, x86@kernel.org Subject: [PATCH v4 2/4] x86/elf: Support a new ELF aux vector AT_MINSIGSTKSZ Date: Fri, 15 Jan 2021 13:10:36 -0800 Message-Id: <20210115211038.2072-3-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210115211038.2072-1-chang.seok.bae@intel.com> References: <20210115211038.2072-1-chang.seok.bae@intel.com> X-Spam-Status: No, score=-10.8 required=5.0 tests=BAYES_00, GIT_PATCH_0, KAM_DMARC_STATUS, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: "Chang S. Bae via Libc-alpha" From: "Chang S. Bae" Reply-To: "Chang S. Bae" Cc: linux-arch@vger.kernel.org, len.brown@intel.com, tony.luck@intel.com, libc-alpha@sourceware.org, ravi.v.shankar@intel.com, chang.seok.bae@intel.com, jannh@google.com, linux-kernel@vger.kernel.org, Fenghua Yu , dave.hansen@intel.com, linux-api@vger.kernel.org, Dave.Martin@arm.com Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" Historically, signal.h defines MINSIGSTKSZ (2KB) and SIGSTKSZ (8KB), for use by all architectures with sigaltstack(2). Over time, the hardware state size grew, but these constants did not evolve. Today, literal use of these constants on several architectures may result in signal stack overflow, and thus user data corruption. A few years ago, the ARM team addressed this issue by establishing getauxval(AT_MINSIGSTKSZ), such that the kernel can supply at runtime value that is an appropriate replacement on the current and future hardware. Add getauxval(AT_MINSIGSTKSZ) support to x86, analogous to the support added for ARM in commit 94b07c1f8c39 ("arm64: signal: Report signal frame size to userspace via auxv"). Reported-by: Florian Weimer Fixes: c2bc11f10a39 ("x86, AVX-512: Enable AVX-512 States Context Switch") Signed-off-by: Chang S. Bae Reviewed-by: Len Brown Cc: H.J. Lu Cc: Fenghua Yu Cc: Dave Martin Cc: Michael Ellerman Cc: x86@kernel.org Cc: libc-alpha@sourceware.org Cc: linux-arch@vger.kernel.org Cc: linux-api@vger.kernel.org Cc: linux-kernel@vger.kernel.org Link: https://bugzilla.kernel.org/show_bug.cgi?id=153531 --- arch/x86/include/asm/elf.h | 4 ++++ arch/x86/include/uapi/asm/auxvec.h | 6 ++++-- arch/x86/kernel/signal.c | 5 +++++ 3 files changed, 13 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index b9a5d488f1a5..044b024abea1 100644 --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -311,6 +311,7 @@ do { \ NEW_AUX_ENT(AT_SYSINFO, VDSO_ENTRY); \ NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_CURRENT_BASE); \ } \ + NEW_AUX_ENT(AT_MINSIGSTKSZ, get_sigframe_size()); \ } while (0) /* @@ -327,6 +328,7 @@ extern unsigned long task_size_32bit(void); extern unsigned long task_size_64bit(int full_addr_space); extern unsigned long get_mmap_base(int is_legacy); extern bool mmap_address_hint_valid(unsigned long addr, unsigned long len); +extern unsigned long get_sigframe_size(void); #ifdef CONFIG_X86_32 @@ -348,6 +350,7 @@ do { \ if (vdso64_enabled) \ NEW_AUX_ENT(AT_SYSINFO_EHDR, \ (unsigned long __force)current->mm->context.vdso); \ + NEW_AUX_ENT(AT_MINSIGSTKSZ, get_sigframe_size()); \ } while (0) /* As a historical oddity, the x32 and x86_64 vDSOs are controlled together. */ @@ -356,6 +359,7 @@ do { \ if (vdso64_enabled) \ NEW_AUX_ENT(AT_SYSINFO_EHDR, \ (unsigned long __force)current->mm->context.vdso); \ + NEW_AUX_ENT(AT_MINSIGSTKSZ, get_sigframe_size()); \ } while (0) #define AT_SYSINFO 32 diff --git a/arch/x86/include/uapi/asm/auxvec.h b/arch/x86/include/uapi/asm/auxvec.h index 580e3c567046..edd7808060e6 100644 --- a/arch/x86/include/uapi/asm/auxvec.h +++ b/arch/x86/include/uapi/asm/auxvec.h @@ -10,11 +10,13 @@ #endif #define AT_SYSINFO_EHDR 33 +#define AT_MINSIGSTKSZ 51 + /* entries in ARCH_DLINFO: */ #if defined(CONFIG_IA32_EMULATION) || !defined(CONFIG_X86_64) -# define AT_VECTOR_SIZE_ARCH 2 +# define AT_VECTOR_SIZE_ARCH 3 #else /* else it's non-compat x86-64 */ -# define AT_VECTOR_SIZE_ARCH 1 +# define AT_VECTOR_SIZE_ARCH 2 #endif #endif /* _ASM_X86_AUXVEC_H */ diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index 138a9f5b78d8..761d856f8ef7 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -716,6 +716,11 @@ void __init init_sigframe_size(void) max_frame_size = round_up(max_frame_size, FRAME_ALIGNMENT); } +unsigned long get_sigframe_size(void) +{ + return max_frame_size; +} + static inline int is_ia32_compat_frame(struct ksignal *ksig) { return IS_ENABLED(CONFIG_IA32_EMULATION) && From patchwork Fri Jan 15 21:10:37 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Chang S. Bae" X-Patchwork-Id: 41726 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 3E910398B162; Fri, 15 Jan 2021 21:15:22 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 3E910398B162 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1610745322; bh=d8pAdpt4Xtk+iSw2F2yNbSUMpaXbZh5W2q3w2ZIx61c=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=gJpRtdDEHi/ihImflpg/nWsrhV8dAD4HtvDSp3vvefGF9tfwkk5By11vOOwcs5eHW Jbx586P3kK2Jvh1ceiSk512QtDQh2t51r9X009o4meMEHF1W/ZKbQD1MICadIrqCva cAY6wFtbRZ9L7XmyweaejXPskAE3Taf3scJ5+SLY= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by sourceware.org (Postfix) with ESMTPS id 6ADD33857C69 for ; Fri, 15 Jan 2021 21:15:20 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 6ADD33857C69 IronPort-SDR: enS/R9y87+ksm4o5i9tdaY4KXhfA4/AzrrIlYsGYmqckE6HPJgW11FtJlnoHUrS/Y+52acrU6g f5UE6kt2DsyQ== X-IronPort-AV: E=McAfee;i="6000,8403,9865"; a="158382275" X-IronPort-AV: E=Sophos;i="5.79,350,1602572400"; d="scan'208";a="158382275" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Jan 2021 13:15:15 -0800 IronPort-SDR: n7CKBxPaxKjx3ZV66DcDZNB4rCprG6ugLaAR6/NGBPP3U0WkIxmg9lSdYhjcH8TYK8vmeXjFvC wymICGm5DwFg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.79,350,1602572400"; d="scan'208";a="401418973" Received: from chang-linux-3.sc.intel.com ([172.25.66.175]) by fmsmga002.fm.intel.com with ESMTP; 15 Jan 2021 13:15:15 -0800 To: bp@suse.de, tglx@linutronix.de, mingo@kernel.org, luto@kernel.org, x86@kernel.org Subject: [PATCH v4 3/4] x86/signal: Detect and prevent an alternate signal stack overflow Date: Fri, 15 Jan 2021 13:10:37 -0800 Message-Id: <20210115211038.2072-4-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210115211038.2072-1-chang.seok.bae@intel.com> References: <20210115211038.2072-1-chang.seok.bae@intel.com> X-Spam-Status: No, score=-10.9 required=5.0 tests=BAYES_00, GIT_PATCH_0, KAM_DMARC_STATUS, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: "Chang S. Bae via Libc-alpha" From: "Chang S. Bae" Reply-To: "Chang S. Bae" Cc: linux-arch@vger.kernel.org, len.brown@intel.com, tony.luck@intel.com, libc-alpha@sourceware.org, ravi.v.shankar@intel.com, chang.seok.bae@intel.com, jannh@google.com, linux-kernel@vger.kernel.org, dave.hansen@intel.com, Borislav Petkov , linux-api@vger.kernel.org, Dave.Martin@arm.com Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" The kernel pushes context on to the userspace stack to prepare for the user's signal handler. When the user has supplied an alternate signal stack, via sigaltstack(2), it is easy for the kernel to verify that the stack size is sufficient for the current hardware context. Check if writing the hardware context to the alternate stack will exceed it's size. If yes, then instead of corrupting user-data and proceeding with the original signal handler, an immediate SIGSEGV signal is delivered. While previous patches in this series allow new source code to discover and use a sufficient alternate signal stack size, this check is still necessary to protect binaries with insufficient alternate signal stack size from data corruption. Suggested-by: Jann Horn Signed-off-by: Chang S. Bae Reviewed-by: Len Brown Reviewed-by: Jann Horn Cc: Borislav Petkov Cc: Jann Horn Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org --- Changes from v3: * Updated the changelog (Borislav Petkov) Changes from v2: * Simplified the implementation (Jann Horn) --- arch/x86/kernel/signal.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index 761d856f8ef7..91056a940271 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -242,7 +242,7 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size, unsigned long math_size = 0; unsigned long sp = regs->sp; unsigned long buf_fx = 0; - int onsigstack = on_sig_stack(sp); + bool onsigstack = on_sig_stack(sp); int ret; /* redzone */ @@ -251,8 +251,11 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size, /* This is the X/Open sanctioned signal stack switching. */ if (ka->sa.sa_flags & SA_ONSTACK) { - if (sas_ss_flags(sp) == 0) + if (sas_ss_flags(sp) == 0) { sp = current->sas_ss_sp + current->sas_ss_size; + /* On the alternate signal stack */ + onsigstack = true; + } } else if (IS_ENABLED(CONFIG_X86_32) && !onsigstack && regs->ss != __USER_DS && From patchwork Fri Jan 15 21:10:38 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Chang S. Bae" X-Patchwork-Id: 41727 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id B86CA398B168; Fri, 15 Jan 2021 21:15:24 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org B86CA398B168 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1610745324; bh=ctw/IUE7Q7HrR8mjSfnN7F7MB5lkgO1AuZo0hcHa8Uw=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=Uibd9415evW6fEVIwSGQGWmh2srNVVH83TxUNy1/2Tj3YP8hbnVbdDPwjcZ9o+Kz3 OKn5EwlQeSufThW/et7hZY99O6Yg7q4jPQjDO2BN2jbB8bQIUxiUs7mIkUeYUBk3uj CyOgvrSWPXoDG3lsbc/HMQ40rwLg4mjIVYycWasY= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by sourceware.org (Postfix) with ESMTPS id CEC6A3987C39 for ; Fri, 15 Jan 2021 21:15:20 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org CEC6A3987C39 IronPort-SDR: xIwOad8UDjkd2PyDTCDST16D7hk3kLKraTbb5SYZAFuS6x9JX+4M1/VRg3f6qyFo7+FIboQCCd YC/kxjGAz+oA== X-IronPort-AV: E=McAfee;i="6000,8403,9865"; a="158382276" X-IronPort-AV: E=Sophos;i="5.79,350,1602572400"; d="scan'208";a="158382276" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 15 Jan 2021 13:15:15 -0800 IronPort-SDR: 40vyABUWaWhyy4NQfmGRrBAid59rOdBgKOB6fF8wFnweKcu15M6rqOW4vTMcaiD8N7j/ZJytLG Vm5m/mct4GIg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.79,350,1602572400"; d="scan'208";a="401418976" Received: from chang-linux-3.sc.intel.com ([172.25.66.175]) by fmsmga002.fm.intel.com with ESMTP; 15 Jan 2021 13:15:15 -0800 To: bp@suse.de, tglx@linutronix.de, mingo@kernel.org, luto@kernel.org, x86@kernel.org Subject: [PATCH v4 4/4] selftest/x86/signal: Include test cases for validating sigaltstack Date: Fri, 15 Jan 2021 13:10:38 -0800 Message-Id: <20210115211038.2072-5-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210115211038.2072-1-chang.seok.bae@intel.com> References: <20210115211038.2072-1-chang.seok.bae@intel.com> X-Spam-Status: No, score=-10.9 required=5.0 tests=BAYES_00, GIT_PATCH_0, KAM_DMARC_STATUS, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: "Chang S. Bae via Libc-alpha" From: "Chang S. Bae" Reply-To: "Chang S. Bae" Cc: linux-arch@vger.kernel.org, len.brown@intel.com, tony.luck@intel.com, libc-alpha@sourceware.org, ravi.v.shankar@intel.com, chang.seok.bae@intel.com, jannh@google.com, linux-kernel@vger.kernel.org, dave.hansen@intel.com, Borislav Petkov , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, Dave.Martin@arm.com Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" The test measures the kernel's signal delivery with different (enough vs. insufficient) stack sizes. Signed-off-by: Chang S. Bae Reviewed-by: Len Brown Cc: Borislav Petkov Cc: x86@kernel.org Cc: linux-kselftest@vger.kernel.org Cc: linux-kernel@vger.kernel.org --- Changes from v3: * Revised test messages again (Borislav Petkov) Changes from v2: * Revised test messages (Borislav Petkov) --- tools/testing/selftests/x86/Makefile | 2 +- tools/testing/selftests/x86/sigaltstack.c | 128 ++++++++++++++++++++++ 2 files changed, 129 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/x86/sigaltstack.c diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile index 6703c7906b71..e0c52e5ab49e 100644 --- a/tools/testing/selftests/x86/Makefile +++ b/tools/testing/selftests/x86/Makefile @@ -13,7 +13,7 @@ CAN_BUILD_WITH_NOPIE := $(shell ./check_cc.sh $(CC) trivial_program.c -no-pie) TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt test_mremap_vdso \ check_initial_reg_state sigreturn iopl ioperm \ test_vdso test_vsyscall mov_ss_trap \ - syscall_arg_fault fsgsbase_restore + syscall_arg_fault fsgsbase_restore sigaltstack TARGETS_C_32BIT_ONLY := entry_from_vm86 test_syscall_vdso unwind_vdso \ test_FCMOV test_FCOMI test_FISTTP \ vdso_restorer diff --git a/tools/testing/selftests/x86/sigaltstack.c b/tools/testing/selftests/x86/sigaltstack.c new file mode 100644 index 000000000000..f689af75e979 --- /dev/null +++ b/tools/testing/selftests/x86/sigaltstack.c @@ -0,0 +1,128 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* sigaltstack()-enforced minimum stack */ +#define ENFORCED_MINSIGSTKSZ 2048 + +#ifndef AT_MINSIGSTKSZ +# define AT_MINSIGSTKSZ 51 +#endif + +static int nerrs; + +static bool sigalrm_expected; + +static unsigned long at_minstack_size; + +static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *), + int flags) +{ + struct sigaction sa; + + memset(&sa, 0, sizeof(sa)); + sa.sa_sigaction = handler; + sa.sa_flags = SA_SIGINFO | flags; + sigemptyset(&sa.sa_mask); + if (sigaction(sig, &sa, 0)) + err(1, "sigaction"); +} + +static void clearhandler(int sig) +{ + struct sigaction sa; + + memset(&sa, 0, sizeof(sa)); + sa.sa_handler = SIG_DFL; + sigemptyset(&sa.sa_mask); + if (sigaction(sig, &sa, 0)) + err(1, "sigaction"); +} + +static int setup_altstack(void *start, unsigned long size) +{ + stack_t ss; + + memset(&ss, 0, sizeof(ss)); + ss.ss_size = size; + ss.ss_sp = start; + + return sigaltstack(&ss, NULL); +} + +static jmp_buf jmpbuf; + +static void sigsegv(int sig, siginfo_t *info, void *ctx_void) +{ + if (sigalrm_expected) { + printf("[FAIL]\tWrong signal delivered: SIGSEGV (expected SIGALRM)."); + nerrs++; + } else { + printf("[OK]\tSIGSEGV signal delivered.\n"); + } + + siglongjmp(jmpbuf, 1); +} + +static void sigalrm(int sig, siginfo_t *info, void *ctx_void) +{ + if (!sigalrm_expected) { + printf("[FAIL]\tWrong signal delivered: SIGALRM (expected SIGSEGV)."); + nerrs++; + } else { + printf("[OK]\tSIGALRM signal delivered.\n"); + } +} + +static void test_sigaltstack(void *altstack, unsigned long size) +{ + if (setup_altstack(altstack, size)) + err(1, "sigaltstack()"); + + sigalrm_expected = (size > at_minstack_size) ? true : false; + + sethandler(SIGSEGV, sigsegv, 0); + sethandler(SIGALRM, sigalrm, SA_ONSTACK); + + if (!sigsetjmp(jmpbuf, 1)) { + printf("[RUN]\tTest an alternate signal stack of %ssufficient size.\n", + sigalrm_expected ? "" : "in"); + printf("\tRaise SIGALRM. %s is expected to be delivered.\n", + sigalrm_expected ? "It" : "SIGSEGV"); + raise(SIGALRM); + } + + clearhandler(SIGALRM); + clearhandler(SIGSEGV); +} + +int main(void) +{ + void *altstack; + + at_minstack_size = getauxval(AT_MINSIGSTKSZ); + + altstack = mmap(NULL, at_minstack_size + SIGSTKSZ, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0); + if (altstack == MAP_FAILED) + err(1, "mmap()"); + + if ((ENFORCED_MINSIGSTKSZ + 1) < at_minstack_size) + test_sigaltstack(altstack, ENFORCED_MINSIGSTKSZ + 1); + + test_sigaltstack(altstack, at_minstack_size + SIGSTKSZ); + + return nerrs == 0 ? 0 : 1; +}