From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8784FC54F4C for ; Tue, 28 Jul 2026 13:08:27 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 71DD96B0099; Tue, 28 Jul 2026 09:08:26 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6D01B6B009B; Tue, 28 Jul 2026 09:08:26 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5BD176B009D; Tue, 28 Jul 2026 09:08:26 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 203366B0099 for ; Tue, 28 Jul 2026 09:08:26 -0400 (EDT) Received: from smtpin24.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id A2B2B14037D for ; Tue, 28 Jul 2026 13:08:25 +0000 (UTC) X-FDA: 85038214170.24.E7E894C Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf19.hostedemail.com (Postfix) with ESMTP id C8AD51A000F for ; Tue, 28 Jul 2026 13:08:23 +0000 (UTC) Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=lkVctXdO; spf=pass (imf19.hostedemail.com: domain of rppt@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1785244103; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Z6kR497LjC7Isvr03okKrlj74MLRITXjjuRFnxSRHOw=; b=cy1aKaSLWrh84GT+q2fRkyWJFzBsJ4ysWLGj1oPVA6Co5ZISlu40FTOdpHUvQrzETiBNJ/ oF3kuf5fjv5uRmQzG2wV28aEQJniFFlfbP4+d8yTwwj71Wp6zQtqHa7iosU9EAs5UsOc/y b+dRY6f+8EnTXyj/WzNVHk1Yxf7b7v8= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1785244103; b=At5HupPxfR85pdnDz7c3bv7nqETJfjODY4E9JCGMO+5mHNPkPNNxH3KxVIPclYP2pSntkZ r2EWXC975K8bDWyBGjpiMXvDOrs34Oz8E+GVT743wXSuZjqNrGZU4sNO9LnBVtonrSHYPJ 0LfFrf07UHMUVgHPc7dfjl2qEaie3qA= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=lkVctXdO; spf=pass (imf19.hostedemail.com: domain of rppt@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 523A360A96; Tue, 28 Jul 2026 13:08:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0692C1F00A3A; Tue, 28 Jul 2026 13:08:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785244103; bh=Z6kR497LjC7Isvr03okKrlj74MLRITXjjuRFnxSRHOw=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=lkVctXdO80DTaLpIRkVUNPaBSSApcMdOEjwGOtWKWkmUaJkBC2uenMket0s0+WK+J qTU2b4h1fS76z1+BcoV+nXD1jokWc4Q75GzqaJk/fzbQbRLt/zhxBM+bEY7fykoTor 4WRIpmFOp61kxIYTDeLHD8DyJnWLF3jKgtl9yoh+6oG9D2fAMp4y5aWgahNyjkUet0 7gH3rlRAr5V7wVuKeildwuQTH2IpBnJ1T67rSxZHP6K4raL9pwTFSFTkZn6/G1i4bv y1BSGF0PnqNg4eE/SU78DganA84psQAVYfEmnZlG5sbg36lAUorwUcutXzBn/yOMwT IpmJaUtdaoQ2g== From: Mike Rapoport Date: Tue, 28 Jul 2026 16:07:45 +0300 Subject: [PATCH 2/5] x86/mm/pat: acquire init_mm write lock on collapse to avoid UAF MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260728-cpa-fixes-v1-2-2ed2352300b3@kernel.org> References: <20260728-cpa-fixes-v1-0-2ed2352300b3@kernel.org> In-Reply-To: <20260728-cpa-fixes-v1-0-2ed2352300b3@kernel.org> To: Dave Hansen Cc: Andrew Morton , Andy Lutomirski , Borislav Petkov , David CARLIER , David Hildenbrand , Ingo Molnar , Jason Gunthorpe , Juergen Gross , Kevin Tian , Kiryl Shutsemau , "Liam R. Howlett" , Lorenzo Stoakes , Lu Baolu , Mike Rapoport , "H. Peter Anvin" , Peter Zijlstra , Shakeel Butt , Suren Baghdasaryan , Thomas Gleixner , Toshi Kani , Vishal Moola , Vlastimil Babka , Will Deacon , iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, x86@kernel.org X-Mailer: b4 0.16-dev X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: C8AD51A000F X-Stat-Signature: bmow8j8b6fw4zg58r8i1mxpmirxjydas X-Rspam-User: X-HE-Tag: 1785244103-874434 X-HE-Meta: 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 B554i1bk oYRQl93MRf/G9Yk/wvhnrkSGoRddsGu1Jfz27qtoImBmdQYGjCrwxsngoFq8J941VxHuAYceSXG8qR9+mQwG8trlwCyOtkohVCaIEWGOH3YbxRoEfpy8bo8UYypwLYoKU64SjkUNKI5bCZgvdQREaBmRWocvXLqCdmn0ykFTVN0yvsS6iK3CPOmuOrz/zLMDRSd10q9FnfkW2TI0Gmnkrru3xylF503Aj3PG/K4CS4/pElZ5OlMZUIObd1u7HI2YKYYWCErpN9thBkx0YlRszTpUzsnYa5z7N+UV5XmIfuMu7MBUmDJ4bo1B+HhsXXLA80fRPoJd2qdu80UvDJbDXd6s1YUZl4DdLdIDGeIjftn47u08zPZ/Zmogk0mnDAI46bzekcD0PZriKsNr0djpVzNUUzexvLpA8esDp Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: "Lorenzo Stoakes (ARM)" x86 implements page attribute modification using its Change Page Attributes (CPA) mechanism. This tracks properties of ranges such as cache mode through x86 page attributes, and as part of that logic manipulates kernel page tables. Since commit 41d88484c71c ("x86/mm/pat: restore large ROX pages after fragmentation") ranges of kernel page table entries can be collapsed into huge page table entries as part of this logic. As part of this collapse, it frees the page tables which the collapsed entries previously pointed to, and it does so without any relevant locks being held to preclude concurrent kernel page table walkers. The only way this code can be reached is if CPA_COLLAPSE is specified, and this is only set in set_memory_rox() via: set_memory_rox() -> change_page_attr_set_clr() -> cpa_flush() -> cpa_collapse_large_pages() Notable users of this are execmem and bpf when manipulating executable mappings. However, this is problematic for ptdump as it walks ranges it does not own and thus runs the risk of a use-after-free on page tables freed underneath it. In addition, concurrent CPA collapse operations are possible which can also cause races. Resolve the issue by acquiring the mmap write lock on init_mm across the whole operation. It is safe to acquire a sleeping lock as all the callers invoke set_memory_rox() from process context and in any case, change_page_attr_set_clr() calls vm_unmap_alias() which ultimately takes a mutex, disallowing atomic context here. Fixes: 41d88484c71c ("x86/mm/pat: restore large ROX pages after fragmentation") Cc: stable@vger.kernel.org Reviewed-by: Mike Rapoport (Microsoft) Reviewed-by: Kiryl Shutsemau (Meta) Reviewed-by: David Hildenbrand (Arm) Reviewed-by: Dave Hansen Reviewed-by: Will Deacon Reviewed-by: David Carlier Signed-off-by: Lorenzo Stoakes (ARM) Signed-off-by: Mike Rapoport (Microsoft) --- arch/x86/mm/pat/set_memory.c | 15 ++++++++++++++- include/linux/mmap_lock.h | 2 ++ 2 files changed, 16 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c index 4c8922695fd3..4ba16d72a535 100644 --- a/arch/x86/mm/pat/set_memory.c +++ b/arch/x86/mm/pat/set_memory.c @@ -22,6 +22,7 @@ #include #include #include +#include #include #include @@ -426,7 +427,7 @@ static void __cpa_flush_tlb(void *data) static int collapse_large_pages(unsigned long addr, struct list_head *pgtables); -static void cpa_collapse_large_pages(struct cpa_data *cpa) +static void __cpa_collapse_large_pages(struct cpa_data *cpa) { unsigned long start, addr, end; struct ptdesc *ptdesc, *tmp; @@ -464,6 +465,18 @@ static void cpa_collapse_large_pages(struct cpa_data *cpa) cpa_unlock(); } +static void cpa_collapse_large_pages(struct cpa_data *cpa) +{ + /* + * Take the mmap write lock on init_mm to: + * - Avoid a use-after-free if raced by ptdump (which takes its own + * write lock on init_mm). + * - Serialise concurrent CPA walkers. + */ + scoped_guard(mmap_write_lock, &init_mm) + __cpa_collapse_large_pages(cpa); +} + static void cpa_flush(struct cpa_data *cpa, int cache) { unsigned int i; diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h index 04b8f61ece5d..f4ceb968aeb3 100644 --- a/include/linux/mmap_lock.h +++ b/include/linux/mmap_lock.h @@ -621,6 +621,8 @@ static inline void mmap_read_unlock(struct mm_struct *mm) DEFINE_GUARD(mmap_read_lock, struct mm_struct *, mmap_read_lock(_T), mmap_read_unlock(_T)) +DEFINE_GUARD(mmap_write_lock, struct mm_struct *, + mmap_write_lock(_T), mmap_write_unlock(_T)) static inline void mmap_read_unlock_non_owner(struct mm_struct *mm) { -- 2.53.0