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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4EB6DECAAA1 for ; Tue, 6 Sep 2022 13:36:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240595AbiIFNgz (ORCPT ); Tue, 6 Sep 2022 09:36:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52844 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240601AbiIFNfq (ORCPT ); Tue, 6 Sep 2022 09:35:46 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 57BA4785AB; Tue, 6 Sep 2022 06:34:08 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 8F1C061545; Tue, 6 Sep 2022 13:34:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8F573C433C1; Tue, 6 Sep 2022 13:34:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1662471247; bh=Y41acJnPbIPvCDAOYp8tN09jfsIFrbQaNS7WKC7F12M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gsc5OqTS9O+o8v9kirzHC3QKyg25fWKRUqgjSjf4qwRBiQ6jNiOc2g5EoqI/KqQrq lZ5k7CG/hPkZBMPDwaDEYxFXEc/FmZpiIIPQC7GXKao/7AdcGMlDabnRk/C0UX0gM9 +YrUCVr7N8c8TRfNJXyNLoRMGRYqseevToBsie6E= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jann Horn , Steven Price , Vlastimil Babka , =?UTF-8?q?Thomas=20Hellstr=C3=B6m?= , Konstantin Khlebnikov , Andrew Morton , Linus Torvalds , Sasha Levin Subject: [PATCH 5.10 46/80] mm: pagewalk: Fix race between unmap and page walker Date: Tue, 6 Sep 2022 15:30:43 +0200 Message-Id: <20220906132818.928764652@linuxfoundation.org> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20220906132816.936069583@linuxfoundation.org> References: <20220906132816.936069583@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Steven Price [ Upstream commit 8782fb61cc848364e1e1599d76d3c9dd58a1cc06 ] The mmap lock protects the page walker from changes to the page tables during the walk. However a read lock is insufficient to protect those areas which don't have a VMA as munmap() detaches the VMAs before downgrading to a read lock and actually tearing down PTEs/page tables. For users of walk_page_range() the solution is to simply call pte_hole() immediately without checking the actual page tables when a VMA is not present. We now never call __walk_page_range() without a valid vma. For walk_page_range_novma() the locking requirements are tightened to require the mmap write lock to be taken, and then walking the pgd directly with 'no_vma' set. This in turn means that all page walkers either have a valid vma, or it's that special 'novma' case for page table debugging. As a result, all the odd '(!walk->vma && !walk->no_vma)' tests can be removed. Fixes: dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap") Reported-by: Jann Horn Signed-off-by: Steven Price Cc: Vlastimil Babka Cc: Thomas Hellström Cc: Konstantin Khlebnikov Cc: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- arch/riscv/mm/pageattr.c | 4 ++-- mm/pagewalk.c | 21 ++++++++++++--------- mm/ptdump.c | 4 ++-- 3 files changed, 16 insertions(+), 13 deletions(-) diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c index 19fecb362d815..09f6be19ba7b3 100644 --- a/arch/riscv/mm/pageattr.c +++ b/arch/riscv/mm/pageattr.c @@ -118,10 +118,10 @@ static int __set_memory(unsigned long addr, int numpages, pgprot_t set_mask, if (!numpages) return 0; - mmap_read_lock(&init_mm); + mmap_write_lock(&init_mm); ret = walk_page_range_novma(&init_mm, start, end, &pageattr_ops, NULL, &masks); - mmap_read_unlock(&init_mm); + mmap_write_unlock(&init_mm); flush_tlb_kernel_range(start, end); diff --git a/mm/pagewalk.c b/mm/pagewalk.c index e81640d9f1770..371ec21a19899 100644 --- a/mm/pagewalk.c +++ b/mm/pagewalk.c @@ -71,7 +71,7 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end, do { again: next = pmd_addr_end(addr, end); - if (pmd_none(*pmd) || (!walk->vma && !walk->no_vma)) { + if (pmd_none(*pmd)) { if (ops->pte_hole) err = ops->pte_hole(addr, next, depth, walk); if (err) @@ -129,7 +129,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end, do { again: next = pud_addr_end(addr, end); - if (pud_none(*pud) || (!walk->vma && !walk->no_vma)) { + if (pud_none(*pud)) { if (ops->pte_hole) err = ops->pte_hole(addr, next, depth, walk); if (err) @@ -318,19 +318,19 @@ static int __walk_page_range(unsigned long start, unsigned long end, struct vm_area_struct *vma = walk->vma; const struct mm_walk_ops *ops = walk->ops; - if (vma && ops->pre_vma) { + if (ops->pre_vma) { err = ops->pre_vma(start, end, walk); if (err) return err; } - if (vma && is_vm_hugetlb_page(vma)) { + if (is_vm_hugetlb_page(vma)) { if (ops->hugetlb_entry) err = walk_hugetlb_range(start, end, walk); } else err = walk_pgd_range(start, end, walk); - if (vma && ops->post_vma) + if (ops->post_vma) ops->post_vma(walk); return err; @@ -402,9 +402,13 @@ int walk_page_range(struct mm_struct *mm, unsigned long start, if (!vma) { /* after the last vma */ walk.vma = NULL; next = end; + if (ops->pte_hole) + err = ops->pte_hole(start, next, -1, &walk); } else if (start < vma->vm_start) { /* outside vma */ walk.vma = NULL; next = min(end, vma->vm_start); + if (ops->pte_hole) + err = ops->pte_hole(start, next, -1, &walk); } else { /* inside vma */ walk.vma = vma; next = min(end, vma->vm_end); @@ -422,9 +426,8 @@ int walk_page_range(struct mm_struct *mm, unsigned long start, } if (err < 0) break; - } - if (walk.vma || walk.ops->pte_hole) err = __walk_page_range(start, next, &walk); + } if (err) break; } while (start = next, start < end); @@ -453,9 +456,9 @@ int walk_page_range_novma(struct mm_struct *mm, unsigned long start, if (start >= end || !walk.mm) return -EINVAL; - mmap_assert_locked(walk.mm); + mmap_assert_write_locked(walk.mm); - return __walk_page_range(start, end, &walk); + return walk_pgd_range(start, end, &walk); } int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops, diff --git a/mm/ptdump.c b/mm/ptdump.c index 93f2f63dc52dc..a917bf55c61ea 100644 --- a/mm/ptdump.c +++ b/mm/ptdump.c @@ -141,13 +141,13 @@ void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd) { const struct ptdump_range *range = st->range; - mmap_read_lock(mm); + mmap_write_lock(mm); while (range->start != range->end) { walk_page_range_novma(mm, range->start, range->end, &ptdump_ops, pgd, st); range++; } - mmap_read_unlock(mm); + mmap_write_unlock(mm); /* Flush out the last page */ st->note_page(st, 0, -1, 0); -- 2.35.1