From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 C570FB663; Tue, 6 Aug 2024 04:39:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722919146; cv=none; b=Ooijd75MmT9fbqqIAJvdmVbivtJ4kLXwaIx0+fC6OR9OYr1H3k0ZfDIPwIMu6+9qsUMXrNZZ4Xe2OL7kpaal/+0Fewg+Uj7VNEvlPtdTRBgTDlY+KmGVVi65LorZQh3NWv4er4pRtv9oNuPpTRQ+P/Vnp7L68qSLoVZQaxQ1cSo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722919146; c=relaxed/simple; bh=8joSK8cgWfzrcf51gsSdZJOHP9od2ZFiV7GhD9Azg7c=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=OnV8zXXLzK+ddWOT7cHiobZ0M7AZQGPxXffFuGqWndHI6m/p01H4tRzUkZSMdNIc6f1pKVboNmFzCRmD1M5eGRi+vb7EneNdOpuTAQb6po6SmPyyGByIyw0WRanld3YzAnkFiqeKEQYvNyzRc6/AL3cvPEw+0lP4N9gCRrIXe/Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Y5kGYjEm; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Y5kGYjEm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1E3AFC32786; Tue, 6 Aug 2024 04:39:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1722919146; bh=8joSK8cgWfzrcf51gsSdZJOHP9od2ZFiV7GhD9Azg7c=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Y5kGYjEmjWQ9+33WhwZ5aZeLeVzTGrlnpEIcqsPnRx+AJxgkBoh4GsMMp7kNUkgvu 1QMGdHCtVmoBH3W6KGXlvqhAMBdPmJq/3XD+zAiE3njHKkvVuw3Y86EazNvHIQ1qtG rRr1zcRpSX7/dRRv+u1s3O2XgaIWeBgnM6Cv8F5TbsCC6K9F8HVTP1espSBF8pLuzj CzxNy1NeT7e+4fCLDJvkdu6o8zFBHRddV5t8hT7DGFcd3o8g5dQiE3afopmyIrl0ch CLs4OS+s0bma+I8oOxY8/VTJQ+30ib9CloeojG16rClEMx99mKVoAqTwN52l5NTghr RwUj/L3AmCgtg== Date: Mon, 5 Aug 2024 21:39:05 -0700 From: Kees Cook To: Gatlin Newhouse Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Marco Elver , Andrey Konovalov , Andrey Ryabinin , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , Andrew Morton , Baoquan He , "Mike Rapoport (IBM)" , Josh Poimboeuf , Changbin Du , Rick Edgecombe , Pengfei Xu , Jason Gunthorpe , Xin Li , Uros Bizjak , "Kirill A. Shutemov" , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-hardening@vger.kernel.org, llvm@lists.linux.dev Subject: Re: [PATCH v5] x86/traps: Enable UBSAN traps on x86 Message-ID: <202408052138.EB7B9788E3@keescook> References: <20240724000206.451425-1-gatlin.newhouse@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240724000206.451425-1-gatlin.newhouse@gmail.com> On Wed, Jul 24, 2024 at 12:01:55AM +0000, Gatlin Newhouse wrote: > Currently ARM architectures extract which specific sanitizer > has caused a trap via encoded data in the trap instruction.[1] > Clang on x86 currently encodes the same data in ud1 instructions > but the x86 handle_bug() and is_valid_bugaddr() functions > currently only look at ud2s. > > Bring x86 to parity with arm64, similar to commit 25b84002afb9 > ("arm64: Support Clang UBSAN trap codes for better reporting"). > Enable the reporting of UBSAN sanitizer detail on x86 architectures > compiled with clang when CONFIG_UBSAN_TRAP=y. > > [1] Details are in llvm/lib/Target/X86/X86MCInstLower.cpp. See: > https://github.com/llvm/llvm-project/commit/c5978f42ec8e9#diff-bb68d7cd885f41cfc35843998b0f9f534adb60b415f647109e597ce448e92d9f > > EmitAndCountInstruction() uses the UD1Lm template, which uses a > OpSize32. See: > https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/X86/X86InstrSystem.td#L27 > > Signed-off-by: Gatlin Newhouse > --- > Changes in v5: > - Added references to the LLVM commits in the commit message from > Kees and Marco's feedback > - Renamed incorrect defines, and removed handle_ubsan_failure()'s > duplicated work per Peter's feedback Ping to the x86 maintainers... can someone pick this up? It looks like all the feedback has been addressed. Thanks! -Kees > > Changes in v4: > - Implement Peter's suggestions for decode_bug(), and fix > inconsistent capitalization in hex values. > > Changes in v3: > - Address Thomas's remarks about: change log structure, > get_ud_type() instead of is_valid_bugaddr(), handle_bug() > changes, and handle_ubsan_failure(). > > Changes in v2: > - Name the new constants 'LEN_ASOP' and 'INSN_ASOP' instead of > 'LEN_REX' and 'INSN_REX' > - Change handle_ubsan_failure() from enum bug_trap_type to void > function > > v1: https://lore.kernel.org/linux-hardening/20240529022043.3661757-1-gatlin.newhouse@gmail.com/ > v2: https://lore.kernel.org/linux-hardening/20240601031019.3708758-1-gatlin.newhouse@gmail.com/ > v3: https://lore.kernel.org/linux-hardening/20240625032509.4155839-1-gatlin.newhouse@gmail.com/ > v4: https://lore.kernel.org/linux-hardening/20240710203250.238782-1-gatlin.newhouse@gmail.com/ > --- > MAINTAINERS | 2 ++ > arch/x86/include/asm/bug.h | 12 ++++++++ > arch/x86/include/asm/ubsan.h | 18 ++++++++++++ > arch/x86/kernel/Makefile | 1 + > arch/x86/kernel/traps.c | 57 ++++++++++++++++++++++++++++++++---- > arch/x86/kernel/ubsan.c | 19 ++++++++++++ > 6 files changed, 104 insertions(+), 5 deletions(-) > create mode 100644 arch/x86/include/asm/ubsan.h > create mode 100644 arch/x86/kernel/ubsan.c > > diff --git a/MAINTAINERS b/MAINTAINERS > index 28e20975c26f..b8512887ffb1 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -22635,6 +22635,8 @@ L: kasan-dev@googlegroups.com > L: linux-hardening@vger.kernel.org > S: Supported > T: git git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/hardening > +F: arch/x86/include/asm/ubsan.h > +F: arch/x86/kernel/ubsan.c > F: Documentation/dev-tools/ubsan.rst > F: include/linux/ubsan.h > F: lib/Kconfig.ubsan > diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h > index a3ec87d198ac..751e45ea27ca 100644 > --- a/arch/x86/include/asm/bug.h > +++ b/arch/x86/include/asm/bug.h > @@ -13,6 +13,18 @@ > #define INSN_UD2 0x0b0f > #define LEN_UD2 2 > > +/* > + * In clang we have UD1s reporting UBSAN failures on X86, 64 and 32bit. > + */ > +#define INSN_ASOP 0x67 > +#define OPCODE_ESCAPE 0x0f > +#define SECOND_BYTE_OPCODE_UD1 0xb9 > +#define SECOND_BYTE_OPCODE_UD2 0x0b > + > +#define BUG_NONE 0xffff > +#define BUG_UD1 0xfffe > +#define BUG_UD2 0xfffd > + > #ifdef CONFIG_GENERIC_BUG > > #ifdef CONFIG_X86_32 > diff --git a/arch/x86/include/asm/ubsan.h b/arch/x86/include/asm/ubsan.h > new file mode 100644 > index 000000000000..1d7c2b4129de > --- /dev/null > +++ b/arch/x86/include/asm/ubsan.h > @@ -0,0 +1,18 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef _ASM_X86_UBSAN_H > +#define _ASM_X86_UBSAN_H > + > +/* > + * Clang Undefined Behavior Sanitizer trap mode support. > + */ > +#include > +#include > +#include > + > +#ifdef CONFIG_UBSAN_TRAP > +void handle_ubsan_failure(struct pt_regs *regs, u32 type); > +#else > +static inline void handle_ubsan_failure(struct pt_regs *regs, u32 type) { return; } > +#endif /* CONFIG_UBSAN_TRAP */ > + > +#endif /* _ASM_X86_UBSAN_H */ > diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile > index 74077694da7d..fe1d9db27500 100644 > --- a/arch/x86/kernel/Makefile > +++ b/arch/x86/kernel/Makefile > @@ -145,6 +145,7 @@ obj-$(CONFIG_UNWINDER_GUESS) += unwind_guess.o > obj-$(CONFIG_AMD_MEM_ENCRYPT) += sev.o > > obj-$(CONFIG_CFI_CLANG) += cfi.o > +obj-$(CONFIG_UBSAN_TRAP) += ubsan.o > > obj-$(CONFIG_CALL_THUNKS) += callthunks.o > > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c > index 4fa0b17e5043..6350d00a6555 100644 > --- a/arch/x86/kernel/traps.c > +++ b/arch/x86/kernel/traps.c > @@ -67,6 +67,7 @@ > #include > #include > #include > +#include > > #ifdef CONFIG_X86_64 > #include > @@ -91,6 +92,45 @@ __always_inline int is_valid_bugaddr(unsigned long addr) > return *(unsigned short *)addr == INSN_UD2; > } > > +/* > + * Check for UD1 or UD2, accounting for Address Size Override Prefixes. > + * If it's a UD1, get the ModRM byte to pass along to UBSan. > + */ > +__always_inline int decode_bug(unsigned long addr, u32 *imm) > +{ > + u8 v; > + > + if (addr < TASK_SIZE_MAX) > + return BUG_NONE; > + > + v = *(u8 *)(addr++); > + if (v == INSN_ASOP) > + v = *(u8 *)(addr++); > + if (v != OPCODE_ESCAPE) > + return BUG_NONE; > + > + v = *(u8 *)(addr++); > + if (v == SECOND_BYTE_OPCODE_UD2) > + return BUG_UD2; > + if (v != SECOND_BYTE_OPCODE_UD1) > + return BUG_NONE; > + > + v = *(u8 *)(addr++); > + if (X86_MODRM_RM(v) == 4) > + addr++; > + > + *imm = 0; > + if (X86_MODRM_MOD(v) == 1) > + *imm = *(u8 *)addr; > + else if (X86_MODRM_MOD(v) == 2) > + *imm = *(u32 *)addr; > + else > + WARN_ONCE(1, "Unexpected MODRM_MOD: %u\n", X86_MODRM_MOD(v)); > + > + return BUG_UD1; > +} > + > + > static nokprobe_inline int > do_trap_no_signal(struct task_struct *tsk, int trapnr, const char *str, > struct pt_regs *regs, long error_code) > @@ -216,6 +256,8 @@ static inline void handle_invalid_op(struct pt_regs *regs) > static noinstr bool handle_bug(struct pt_regs *regs) > { > bool handled = false; > + int ud_type; > + u32 imm; > > /* > * Normally @regs are unpoisoned by irqentry_enter(), but handle_bug() > @@ -223,7 +265,8 @@ static noinstr bool handle_bug(struct pt_regs *regs) > * irqentry_enter(). > */ > kmsan_unpoison_entry_regs(regs); > - if (!is_valid_bugaddr(regs->ip)) > + ud_type = decode_bug(regs->ip, &imm); > + if (ud_type == BUG_NONE) > return handled; > > /* > @@ -236,10 +279,14 @@ static noinstr bool handle_bug(struct pt_regs *regs) > */ > if (regs->flags & X86_EFLAGS_IF) > raw_local_irq_enable(); > - if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN || > - handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN) { > - regs->ip += LEN_UD2; > - handled = true; > + if (ud_type == BUG_UD2) { > + if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN || > + handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN) { > + regs->ip += LEN_UD2; > + handled = true; > + } > + } else { > + handle_ubsan_failure(regs, imm); > } > if (regs->flags & X86_EFLAGS_IF) > raw_local_irq_disable(); > diff --git a/arch/x86/kernel/ubsan.c b/arch/x86/kernel/ubsan.c > new file mode 100644 > index 000000000000..63f819928820 > --- /dev/null > +++ b/arch/x86/kernel/ubsan.c > @@ -0,0 +1,19 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Clang Undefined Behavior Sanitizer trap mode support. > + */ > +#include > +#include > +#include > +#include > +#include > +#include > + > +/* > + * Checks for the information embedded in the UD1 trap instruction > + * for the UB Sanitizer in order to pass along debugging output. > + */ > +void handle_ubsan_failure(struct pt_regs *regs, u32 type) > +{ > + pr_crit("%s at %pS\n", report_ubsan_failure(regs, type), (void *)regs->ip); > +} > -- > 2.25.1 > -- Kees Cook