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 49574314D2F; Fri, 21 Nov 2025 13:42:53 +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=1763732573; cv=none; b=iLRxm2QGsSkSMo9YP7wSB2D1GTH/NwnJjoihuJJkFuDBlQiw3F6unEc4PoYdtr/COE54nKTIwG25MmdgNksT06UQqLU43xmTQaVeapkaRRWhfJX8bwdHdJEbNVEUZ6Ajca109cGOE1Nq8qFN5NA2iQrPZj2SvImB4aJ9eM76yCE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763732573; c=relaxed/simple; bh=2Ru2fWAVOnQf+wO1o0CsraSof6O0ZHcB+XfYnhrjmSc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=WZ5K/HVzAp/Q/Lln0n4WdOz6t4nBoB7kZy5ECgQX6gamBnt7xVSi/HIAX6vsZB+FS3s5+KpIoR27uJBNdqjMI0AmZm9mlur1x1XtnK/nSstk3ivkkhwQDkMUOEH14VYMhsJMmNOwVw7QUHFHZjw63cDALVOJ/sn0vsByzqtpRiY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=qLSOoBwD; 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="qLSOoBwD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B9D1EC4CEF1; Fri, 21 Nov 2025 13:42:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1763732573; bh=2Ru2fWAVOnQf+wO1o0CsraSof6O0ZHcB+XfYnhrjmSc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qLSOoBwDp53X/DB/e6nMLHv0hHaJR/y6s4LMF6uMQ9MJO4pH+BFfiW9+PDoFdgTyo yMl1WrCApdL5qRQPdVTxPlpjfD/2u9NIz0vPWOlzjbbwND5em0cnXlurOABR3kzcYV K9TvL3LCje6MrLJijbVsynFPFiIomDh7aN0dRlrY= 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 6.6 135/529] x86/vsyscall: Do not require X86_PF_INSTR to emulate vsyscall Date: Fri, 21 Nov 2025 14:07:14 +0100 Message-ID: <20251121130235.823157088@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251121130230.985163914@linuxfoundation.org> References: <20251121130230.985163914@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 6.6-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