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 0DBE9265CC5; Tue, 11 Nov 2025 01:07:34 +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=1762823255; cv=none; b=RndOM7/EWWmVDr0ANArPP99MgZvXp84SJq6xcR3IfFTPiT0UpShxCKUwroGSkzqqUgFOeaD3m3fsVuRUNxc7pgSBDZVClyqwq0kCG9DAzqDnyNMwWiShDAuzUmmQhY9j/Z3Q/Zzf1kkKT/TP/6uZtIt+yrxH2h7IbNpq/1fpj4c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762823255; c=relaxed/simple; bh=r+MwlFImFYGpFKDe464zxPfTNsUr6ldc1NeGpRzZ/yM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=i5CKmLISdE/mZtcAwTmy2kBO4MPOOoct+pSxFa8DJf34pZAqFFrI6BWud5Sck3wNvE4fOwHPKV+p2Lf9qYqCAQ8lqGzDIPde/L27NdHVydsfbcQmJ9EclW/YEUQ3ekEZZEbbAWHuqkuEHcwnJcWz9IWEPFW4wfOQqCtv6K1K9mQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=FczUXpzQ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="FczUXpzQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4544FC116B1; Tue, 11 Nov 2025 01:07:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1762823254; bh=r+MwlFImFYGpFKDe464zxPfTNsUr6ldc1NeGpRzZ/yM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FczUXpzQHlCHjLIxk06I8XZpFt5sCdgak0NdY+BpYzWjRq4mWX3bEl3nx5CsbR3TF dqNVPapbb05SZa7k8fvXws0Abis8Gj5DGjgGaj1dI3sXkcXHfOkLr6QOAp+HjV1pYb 94dQMZOk3ycTEMUkpFnu1BR/Cp/6v6y76eCRdKK0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Andrew Cooper , "Kirill A. Shutemov" , Dave Hansen , Sasha Levin , Dave Hansen Subject: [PATCH 6.12 206/565] x86/vsyscall: Do not require X86_PF_INSTR to emulate vsyscall Date: Tue, 11 Nov 2025 09:41:02 +0900 Message-ID: <20251111004531.559046011@linuxfoundation.org> X-Mailer: git-send-email 2.51.2 In-Reply-To: <20251111004526.816196597@linuxfoundation.org> References: <20251111004526.816196597@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kirill A. Shutemov [ Upstream commit 8ba38a7a9a699905b84fa97578a8291010dec273 ] emulate_vsyscall() expects to see X86_PF_INSTR in PFEC on a vsyscall page fault, but the CPU does not report X86_PF_INSTR if neither X86_FEATURE_NX nor X86_FEATURE_SMEP are enabled. X86_FEATURE_NX should be enabled on nearly all 64-bit CPUs, except for early P4 processors that did not support this feature. Instead of explicitly checking for X86_PF_INSTR, compare the fault address to RIP. On machines with X86_FEATURE_NX enabled, issue a warning if RIP is equal to fault address but X86_PF_INSTR is absent. [ dhansen: flesh out code comments ] Originally-by: Dave Hansen Reported-by: Andrew Cooper Signed-off-by: Kirill A. Shutemov Signed-off-by: Dave Hansen Reviewed-by: Andrew Cooper Link: https://lore.kernel.org/all/bd81a98b-f8d4-4304-ac55-d4151a1a77ab@intel.com Link: https://lore.kernel.org/all/20250624145918.2720487-1-kirill.shutemov%40linux.intel.com Signed-off-by: Sasha Levin --- arch/x86/entry/vsyscall/vsyscall_64.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c index 2fb7d53cf3338..95e053b0a4bc0 100644 --- a/arch/x86/entry/vsyscall/vsyscall_64.c +++ b/arch/x86/entry/vsyscall/vsyscall_64.c @@ -124,7 +124,12 @@ bool emulate_vsyscall(unsigned long error_code, if ((error_code & (X86_PF_WRITE | X86_PF_USER)) != X86_PF_USER) return false; - if (!(error_code & X86_PF_INSTR)) { + /* + * Assume that faults at regs->ip are because of an + * instruction fetch. Return early and avoid + * emulation for faults during data accesses: + */ + if (address != regs->ip) { /* Failed vsyscall read */ if (vsyscall_mode == EMULATE) return false; @@ -136,13 +141,19 @@ bool emulate_vsyscall(unsigned long error_code, return false; } + /* + * X86_PF_INSTR is only set when NX is supported. When + * available, use it to double-check that the emulation code + * is only being used for instruction fetches: + */ + if (cpu_feature_enabled(X86_FEATURE_NX)) + WARN_ON_ONCE(!(error_code & X86_PF_INSTR)); + /* * No point in checking CS -- the only way to get here is a user mode * trap to a high address, which means that we're in 64-bit user code. */ - WARN_ON_ONCE(address != regs->ip); - if (vsyscall_mode == NONE) { warn_bad_vsyscall(KERN_INFO, regs, "vsyscall attempted with vsyscall=none"); -- 2.51.0