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 175DC46E006 for ; Fri, 11 Sep 2026 11:28:59 +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=1789126154; cv=none; b=WpUz3Ey6lXP24ht02qO1wv4pfzOwo2FZI+DCzUpCjhXSxZBem/beUeVrPN3Tw6cYUspfRdrmf8+3X96mnixmEGwVExR7SVRm888zyJc0dkmT03TIETfaePTFi2fkvrvRNsg34MNhblqtEQ1DIwjYgCmkcWhPq9Dp8h6Ro1+dg7I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789126154; c=relaxed/simple; bh=5qqz5Ehwu6orTjRfaUUeZb45gjomqVQWglbQmOijWb0=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=SoIbxJ/iSVfkuPZ2Uw8ibASFTQe3dtRtEnLIJNA6xJMgJGtnRl5KvkwXktML6A45J/7z0kq0lHs9xwGORsir+VmK8wrUYK4uy16i2OaWDIQhkm0bAAWEHd3AHGPEGP0eyG8OcDmzUP4NCpqwzDxUesnUb3TIq7HB6WmbxBjmTKk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=A2f0gqDW; 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="A2f0gqDW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6AF971F0089A; Fri, 11 Sep 2026 11:28:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789126131; bh=nsSRp8PdyK7jqxwyqAHoe3K2myVb/dPcJ1AFVgoBhm4=; h=From:Date:Subject:To:Cc; b=A2f0gqDW7IjntqtLnmWTY9FTZt2kpRTwAR81OQ0+X5rLtkU/oM3woCD8mBXpKl22g FxYe3TsxS68ynHwnCCJsl1bwPDgBbcj3b1Txifi+2tin8nkRKoyJzvInE1BZQaJEX1 SfEvjpltcAkNn5xhvf+Rc0Gw+3IiqappNVYNQ4vVHGBz9KbXFSFUbvXeKjGQTNnKQe oQ8qUrbxCW07kqROwNWcZveAksa3yuRMFG/yhKpWZZTaXd6Lv/XEL9aASh6XtvTLuq biMrXtbaqD7QwD7g67lAzMIJsCVJbU2WmOQf4Qz7SKN0f6wro+FrvrrGb/qQcA7fJ7 xshTLjIDUbIHA== From: "Mike Rapoport (Microsoft)" Date: Fri, 11 Sep 2026 14:28:43 +0300 Subject: [PATCH v2] x86/mm/pat: use pr_warn() for early W^X warnings 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="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260911-fixes-verify-rwx-v2-1-e2cde39b6693@kernel.org> X-B4-Tracking: v=1; b=H4sIAAAAAAAC/y2O0RKCIBBFf6XhORSRUeyp/2h8AFuVSnQWMh3Hf w+sx7N7z93diAM04MjltBGE2Tgz2gD8fCJNr2wH1NwDE854waqM0dYs4OgcrHal+FkoE0KKTJe FyiUJ2oRwZIJ1q3/s3voBjY89MaGVA6pR2aaPI2+mdJFFOgxx2RvnR1yPh+YslvxvM8kqXuYsE SwwlzSjOE3++gS08EpG7Ei97/sXW54AzNIAAAA= X-Change-ID: 20260910-fixes-verify-rwx-044841b76a38 To: Dave Hansen Cc: Andy Lutomirski , Borislav Petkov , Ihor Solodrai , Ingo Molnar , Mike Rapoport , Nathan Chancellor , "H. Peter Anvin" , Peter Zijlstra , Thomas Gleixner , x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org X-Mailer: b4 0.17-dev 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 --- Changes in v2: - Use pr_warn_once() for early violations instad if skipping them entirely Link to 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..a4f7fe69e6922 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(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), + 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.