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 A4DF947F79F for ; Mon, 21 Sep 2026 10:54:32 +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=1789988074; cv=none; b=jmuJoWPqFnkx6+8MDx3N+vhqs3ffk7gwwWjecQOyOuNHy+xDAtj9m1+uc4kk489x6mCtBu9G5VsKjiSULb6qfPuqrYvkrIWY7Fx4YbWm7l5urxCNLpwadLga6UOtYYJyJXcukUn5zIdxroNqOr5qCU1176o0VzgQFZDKVWsrmpg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789988074; c=relaxed/simple; bh=2N8rLqTFctIDVUmrt/flB7ohBQgf0bUyTA+fwLtYE8Y=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=FlDN/tbF6O3/Q/UIyr5cA6Ai/9l3z+SPIB6MwVllzc/x7cQujXv29/7fhKOJk3az3fCb0B7gnvATvltpTFPNNbEu8odVXp8RGaL01X2vBUxxABpvjxN80+sjJ4dsgPJX7vHlsS92j4GaBPClsDcs8fO8nTp/+9YUA9RPVpyaAmw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=R5ODJA0g; 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="R5ODJA0g" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9BE461F000FF; Mon, 21 Sep 2026 10:54:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789988072; bh=Rjti9mDz9Knd7equnQAAic7A7rHFx56gyrCpEIe4Ags=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=R5ODJA0gSYeGpPQO16SPXSwTOZ8tih3UjpLvQQDcsnZDQz0jAUM4saHZmFTyuAfHr vly+FL7XP8n2A54LqdJyLVsIx9WzJuTO0YLEK0YAbcM5AGvGQrTt6BZ/h851aJfqRN CUKSZGZMDZlJRaG46SDcvG/7ERr48jcVDq8PzSa0WUsDy3OLzpSPGpzp3gVIw9t5Gm 0xtDRYUjSidbnio8BODSultPs4kBweoUhKKW1zhLz5eL+LI80h69YdkdRUaFgmNP27 tmuKmAlLDZv6BPSkkq2obwcJo1SuUOqpSq27Y7QX21+hblbBi1/y66+jlWKqX0E/N4 1Ngql7XGRJ6yA== Date: Mon, 21 Sep 2026 13:54:24 +0300 From: Mike Rapoport To: Dave Hansen Cc: Andy Lutomirski , Borislav Petkov , Ihor Solodrai , Ingo Molnar , Nathan Chancellor , "H. Peter Anvin" , Peter Zijlstra , Thomas Gleixner , x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v3] x86/mm/pat: use pr_warn() for early W^X warnings Message-ID: References: <20260913-fixes-verify-rwx-v3-1-5e1d6a08bd02@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: <20260913-fixes-verify-rwx-v3-1-5e1d6a08bd02@kernel.org> Gentle ping. On Sun, Sep 13, 2026 at 10:37:27AM +0300, Mike Rapoport (Microsoft) wrote: > 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. > > Since the verification of the entire page table with debug_checkwx() has to > be enabled explicitly in the kernel configuration, retain the warning even > if it's bogus, but make it scream less loudly: use pr_warn_once() rather > than WARN_ONCE(). > > The warning can be removed once debug_checkwx() becomes unconditional for > configurations with CONFIG_STRICT_KERNEL_RWX set. > > Reported-by: Nathan Chancellor > Closes: https://lore.kernel.org/all/20260905044253.GA3816371@ax162 > Signed-off-by: Mike Rapoport (Microsoft) > Tested-by: Nathan Chancellor > Tested-by: Ihor Solodrai > --- > v3 changes: > * fix stupid copy-paste error > > v2: https://patch.msgid.link/20260911-fixes-verify-rwx-v2-1-e2cde39b6693@kernel.org > * Use pr_warn_once() for early violations instad if skipping them entirely > > v1: https://lore.kernel.org/all/20260908092730.4002628-1-rppt@kernel.org/ > --- > arch/x86/mm/pat/set_memory.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c > index b3060000da8d1..a799f539287e2 100644 > --- a/arch/x86/mm/pat/set_memory.c > +++ b/arch/x86/mm/pat/set_memory.c > @@ -697,6 +697,21 @@ static inline pgprot_t verify_rwx(pgprot_t old, pgprot_t new, unsigned long star > return new; > > end = start + npg * PAGE_SIZE - 1; > + > + /* > + * If the kernel text is still RWX, gently complain, this could be a > + * false positive. > + * Once debug_checkwx() becomes mandatory for CONFIG_STRICT_KERNEL_RWX, > + * the warning can be removed completely. > + */ > + if (!kernel_set_to_readonly) { > + pr_warn_once("CPA detected W^X violation: %016llx -> %016llx range: 0x%016lx - 0x%016lx PFN %lx\n", > + (unsigned long long)pgprot_val(old), > + (unsigned long long)pgprot_val(new), > + start, end, pfn); > + return new; > + } > + > WARN_ONCE(1, "CPA detected W^X violation: %016llx -> %016llx range: 0x%016lx - 0x%016lx PFN %lx\n", > (unsigned long long)pgprot_val(old), > (unsigned long long)pgprot_val(new), > > --- > base-commit: ebaf7c9bbb1e16523d7036e7e1225ad2dfcc6482 > change-id: 20260910-fixes-verify-rwx-044841b76a38 > > -- > Sincerely yours, > Mike. > -- Sincerely yours, Mike.