From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 EFB3323E330 for ; Tue, 8 Sep 2026 23:33:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788910421; cv=none; b=PY8/jTvmsrdyAvE8RN7Wt3URr/ExHMERhoF7niyNUZisql721mUsGQZesbZRQmJPUZl1o9XQjaANapy3CTfJj8A9cvadQ5bwkWJi+N4Q+X6C99ON1+QNmkZpOUh/KiF5wt3j9OizdynhFZfWbVgvERXELu8X3bCSnq8EWR/uIOc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788910421; c=relaxed/simple; bh=qrLNIG1hJQSxUnZ/3DZVebqrz6cwG9DkV4nRv53ebt0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=RRNBf4orzRTUACrAD1aPD/+sQ1MyBrNc2FvN++HAJ8upeU4A/gHJpMeBoEMgtszvw2J8DAnzDzb2xbCraN/VcX1Q4AJqzGwBmUItM/Vb7208ybhmJDvsiSsqerANxC1USN1pIk5zvkeVtUCpcX7x5ylo38ifbsUZiiGqeNzQLQo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hEOdsXPY; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hEOdsXPY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6786F1F00A3A; Tue, 8 Sep 2026 23:33:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788910419; bh=M/YNoh46F5RVDPowrbPKouyzIWXWEJqi2J64y5A/WtM=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=hEOdsXPY9IdQ4T7RFq/9Zia1kZhrQg+r84MswkaPKCxxtoYpyT5+KIhZZvdChqdNj i5BWEBPIzs320eU9x14ZPQo5azQ1bPqoqsk91i/J7bN2R2/SRNazVx1TM9r/9894Hh bw4ViBqnf6M8o/p9VQam9En5Rh4WNWrbF0fhUY/ANm0GAvIT8oJGYZgIj3N04vUbFx cFhorFekUwrA/31vqbKQwILdiqT2PuQX7cXU6Kw8b/Vjm/dzCgxKSYdSMylVq5Luro fShMVJjChcM0eKs3sQfJO+HCDa1tolIVWiUAgkbPtDw/eqvBSw0SwZ7vyagOknS9bd +HhytQkCC23tA== Date: Tue, 8 Sep 2026 16:33:34 -0700 From: Nathan Chancellor To: Mike Rapoport Cc: Dave Hansen , Andy Lutomirski , Borislav Petkov , Ingo Molnar , "H. Peter Anvin" , Peter Zijlstra , Thomas Gleixner , linux-kernel@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH] x86/mm/pat: skip RWX verification until kernel text is set to read only Message-ID: <20260908233334.GA2902183@ax162> References: <20260908092730.4002628-1-rppt@kernel.org> 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: <20260908092730.4002628-1-rppt@kernel.org> On Tue, Sep 08, 2026 at 12:27:30PM +0300, Mike Rapoport wrote: > From: "Mike Rapoport (Microsoft)" > > Nathan Chancellor reports the following warning: > > CPA detected W^X violation: 8000000000000123 -> 0000000000000123 range: 0xffffffffc0400000 - 0xffffffffc0400fff PFN 100e00 > WARNING: arch/x86/mm/pat/set_memory.c:722 at __change_page_attr_set_clr+0xde7/0x1290, CPU#0: swapper/0/0 > Modules linked in: > CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 7.3.0-rc1-debug-00006-g453e78594434 #1 PREEMPT(full) 2950d432dd3910251071a66f3134fe0875432786 > Hardware name: ASUS System Product Name/PRIME Z590M-PLUS, BIOS 1801 12/26/2022 > RIP: 0010:__change_page_attr_set_clr+0xdff/0x1290 > Code: 80 7c 24 42 00 0f 85 3a 04 00 00 48 8d 3d 19 8d 79 02 49 89 d9 4c 89 e1 4c 89 d2 4c 89 f6 4d 8d 84 24 ff 0f 00 00 4c 89 14 24 <67> 48 0f b9 3a 4c 8b 14 24 48 8b 0d 81 44 bf 01 41 f6 c2 01 > RSP: 0000:ffffffff87003c60 EFLAGS: 00010246 > RAX: 0000000000000002 RBX: 0000000000100e00 RCX: ffffffffc0400000 > RDX: 0000000000000123 RSI: 8000000000000123 RDI: ffffffff872e50c0 > RBP: 8000000100e00123 R08: ffffffffc0400fff R09: 0000000000100e00 > R10: 0000000000000123 R11: 0000000000000001 R12: ffffffffc0400000 > R13: 0000000100e00123 R14: 8000000000000123 R15: ffffffff87003d58 > FS: 0000000000000000(0000) GS:ffff8ad1777a7000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: ffff8ad0a4201000 CR3: 00000007e3022001 CR4: 0000000000770ef0 > PKRU: 55555554 > Call Trace: > > ? _vm_unmap_aliases+0x219/0x280 > change_page_attr_set_clr+0x161/0x250 > ? events_sysfs_show+0x5d/0x80 > set_memory_x+0x39/0x50 > apply_retpolines+0x656/0x6d0 > ? events_sysfs_show+0x5d/0x80 > ? events_sysfs_show+0x6c/0x80 > ? events_sysfs_show+0x62/0x80 > alternative_instructions+0x3c/0xd0 > arch_cpu_finalize_init+0x130/0x190 > start_kernel+0x97d/0xa10 > x86_64_start_reservations+0x24/0x30 > x86_64_start_kernel+0xda/0xe0 > common_startup_64+0x13e/0x151 > > ---[ end trace 0000000000000000 ]--- > > The warning appears because commit 038176c21617f ("x86/mm/pat: fix > effective RW computation in lookup_address_in_pgd_attr()") fixed the > effective RW checked by verify_rwx() and it exposed that pages used > for ITS trampolines temporarily have RWX permissions. > > The permissions are updated in its_fini_core() after all the ITS > trampolines are generated, but since verify_rwx() detects invalid > transitions, it warns when its_alloc() makes RW memory executable. > > At the time of alternatives patching the entire kernel text is mapped > RWX, so the warning is bogus anyway. > > Skip verification of W^X violations in verify_rwx() when they are > triggered by transitions happening before the kernel text is remapped as > read-only. > > Reported-by: Nathan Chancellor > Closes: https://lore.kernel.org/all/20260905044253.GA3816371@ax162 > Signed-off-by: Mike Rapoport (Microsoft) Tested-by: Nathan Chancellor > --- > arch/x86/mm/pat/set_memory.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c > index 226660973d515..2eecb76703bb4 100644 > --- a/arch/x86/mm/pat/set_memory.c > +++ b/arch/x86/mm/pat/set_memory.c > @@ -708,6 +708,10 @@ static inline pgprot_t verify_rwx(pgprot_t old, pgprot_t new, unsigned long star > if (!(__supported_pte_mask & _PAGE_NX)) > return new; > > + /* skip verification until kernel text is set to read only */ > + if (!kernel_set_to_readonly) > + return new; > + > if (!((pgprot_val(old) ^ pgprot_val(new)) & (_PAGE_RW | _PAGE_NX))) > return new; > > > base-commit: 038176c21617fcc03ccc1ca43230ffedb712c047 > -- > 2.53.0 > -- Cheers, Nathan