From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 38B691F7580; Mon, 23 Jun 2025 22:09:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750716547; cv=none; b=PYWs3QrBYAjanaWjrPERnQik2Y33X3s2cbIr1DXpqgB70YLC81AFOQqC9zAn2WnCYz1koxAytIsUUbFesY5sMV0PSJQu199t59dgMojjCrcTdsjBEazuslErPyZLVSBw3s/RyvEhCgBlGdWc15fzMNJK2BgNETXDBwfjFufNj+U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750716547; c=relaxed/simple; bh=jjpi61QiMuyDQXqZFVMxw1XvnemgenGUhavP+a+0Qd4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tX/7QmYoe7qIEM7HOFN3T0g/C1nNs0e4xcR/RWJLnvyjLjnMM5YENorX2NYgeClByor0hKIeNqe6SiTpFOr4GYlLV/Fw1xAYrEq/QbSh/BGYSd17HMB7wFFKhYWC41c2J9I1LupzN3p+g5dBs3a7PTYCBKIVk/zPuuVRF0ld0QY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=XkzbUGIq; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="XkzbUGIq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8B428C4CEEA; Mon, 23 Jun 2025 22:09:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750716546; bh=jjpi61QiMuyDQXqZFVMxw1XvnemgenGUhavP+a+0Qd4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XkzbUGIqcszdUT4CJcVAZKD3vU8Ir9O7iVwgDAgV7Fh4D18zKw9Du19TQZ7pSos7D DV3fN1gDZiSiexJOITjYvcfJtcjdq5jMC/yQjhStODLrlMmEyuJW4VhHy8eLKfql4B EoCdyDSTNq3WlV+CSczD8R2Vc+oI9WxdRIkdoi+A= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Liu Shixin , Kefeng Wang , Ken Chen , Muchun Song , Nanyong Sun , Jane Chu , Andrew Morton , Jann Horn Subject: [PATCH 5.15 363/411] mm: hugetlb: independent PMD page table shared count Date: Mon, 23 Jun 2025 15:08:27 +0200 Message-ID: <20250623130642.779623727@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250623130632.993849527@linuxfoundation.org> References: <20250623130632.993849527@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Liu Shixin commit 59d9094df3d79443937add8700b2ef1a866b1081 upstream. The folio refcount may be increased unexpectly through try_get_folio() by caller such as split_huge_pages. In huge_pmd_unshare(), we use refcount to check whether a pmd page table is shared. The check is incorrect if the refcount is increased by the above caller, and this can cause the page table leaked: BUG: Bad page state in process sh pfn:109324 page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x66 pfn:0x109324 flags: 0x17ffff800000000(node=0|zone=2|lastcpupid=0xfffff) page_type: f2(table) raw: 017ffff800000000 0000000000000000 0000000000000000 0000000000000000 raw: 0000000000000066 0000000000000000 00000000f2000000 0000000000000000 page dumped because: nonzero mapcount ... CPU: 31 UID: 0 PID: 7515 Comm: sh Kdump: loaded Tainted: G B 6.13.0-rc2master+ #7 Tainted: [B]=BAD_PAGE Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 Call trace: show_stack+0x20/0x38 (C) dump_stack_lvl+0x80/0xf8 dump_stack+0x18/0x28 bad_page+0x8c/0x130 free_page_is_bad_report+0xa4/0xb0 free_unref_page+0x3cc/0x620 __folio_put+0xf4/0x158 split_huge_pages_all+0x1e0/0x3e8 split_huge_pages_write+0x25c/0x2d8 full_proxy_write+0x64/0xd8 vfs_write+0xcc/0x280 ksys_write+0x70/0x110 __arm64_sys_write+0x24/0x38 invoke_syscall+0x50/0x120 el0_svc_common.constprop.0+0xc8/0xf0 do_el0_svc+0x24/0x38 el0_svc+0x34/0x128 el0t_64_sync_handler+0xc8/0xd0 el0t_64_sync+0x190/0x198 The issue may be triggered by damon, offline_page, page_idle, etc, which will increase the refcount of page table. 1. The page table itself will be discarded after reporting the "nonzero mapcount". 2. The HugeTLB page mapped by the page table miss freeing since we treat the page table as shared and a shared page table will not be unmapped. Fix it by introducing independent PMD page table shared count. As described by comment, pt_index/pt_mm/pt_frag_refcount are used for s390 gmap, x86 pgds and powerpc, pt_share_count is used for x86/arm64/riscv pmds, so we can reuse the field as pt_share_count. Link: https://lkml.kernel.org/r/20241216071147.3984217-1-liushixin2@huawei.com Fixes: 39dde65c9940 ("[PATCH] shared page table for hugetlb page") Signed-off-by: Liu Shixin Cc: Kefeng Wang Cc: Ken Chen Cc: Muchun Song Cc: Nanyong Sun Cc: Jane Chu Cc: Signed-off-by: Andrew Morton [backport note: struct ptdesc did not exist yet, stuff it equivalently into struct page instead] Signed-off-by: Jann Horn Signed-off-by: Greg Kroah-Hartman --- include/linux/mm.h | 3 +++ include/linux/mm_types.h | 3 +++ mm/hugetlb.c | 18 ++++++++---------- 3 files changed, 14 insertions(+), 10 deletions(-) --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2352,6 +2352,9 @@ static inline bool pgtable_pmd_page_ctor if (!pmd_ptlock_init(page)) return false; __SetPageTable(page); +#ifdef CONFIG_ARCH_WANT_HUGE_PMD_SHARE + atomic_set(&page->pt_share_count, 0); +#endif inc_lruvec_page_state(page, NR_PAGETABLE); return true; } --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -166,6 +166,9 @@ struct page { union { struct mm_struct *pt_mm; /* x86 pgds only */ atomic_t pt_frag_refcount; /* powerpc */ +#ifdef CONFIG_ARCH_WANT_HUGE_PMD_SHARE + atomic_t pt_share_count; +#endif }; #if ALLOC_SPLIT_PTLOCKS spinlock_t *ptl; --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6046,7 +6046,7 @@ pte_t *huge_pmd_share(struct mm_struct * spte = huge_pte_offset(svma->vm_mm, saddr, vma_mmu_pagesize(svma)); if (spte) { - get_page(virt_to_page(spte)); + atomic_inc(&virt_to_page(spte)->pt_share_count); break; } } @@ -6061,7 +6061,7 @@ pte_t *huge_pmd_share(struct mm_struct * (pmd_t *)((unsigned long)spte & PAGE_MASK)); mm_inc_nr_pmds(mm); } else { - put_page(virt_to_page(spte)); + atomic_dec(&virt_to_page(spte)->pt_share_count); } spin_unlock(ptl); out: @@ -6072,11 +6072,7 @@ out: /* * unmap huge page backed by shared pte. * - * Hugetlb pte page is ref counted at the time of mapping. If pte is shared - * indicated by page_count > 1, unmap is achieved by clearing pud and - * decrementing the ref count. If count == 1, the pte page is not shared. - * - * Called with page table lock held and i_mmap_rwsem held in write mode. + * Called with page table lock held. * * returns: 1 successfully unmapped a shared pte page * 0 the underlying pte page is not shared, or it is the last user @@ -6084,17 +6080,19 @@ out: int huge_pmd_unshare(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long *addr, pte_t *ptep) { + unsigned long sz = huge_page_size(hstate_vma(vma)); pgd_t *pgd = pgd_offset(mm, *addr); p4d_t *p4d = p4d_offset(pgd, *addr); pud_t *pud = pud_offset(p4d, *addr); i_mmap_assert_write_locked(vma->vm_file->f_mapping); - BUG_ON(page_count(virt_to_page(ptep)) == 0); - if (page_count(virt_to_page(ptep)) == 1) + if (sz != PMD_SIZE) + return 0; + if (!atomic_read(&virt_to_page(ptep)->pt_share_count)) return 0; pud_clear(pud); - put_page(virt_to_page(ptep)); + atomic_dec(&virt_to_page(ptep)->pt_share_count); mm_dec_nr_pmds(mm); /* * This update of passed address optimizes loops sequentially