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 0EDEE2494F0; Wed, 8 Apr 2026 18:25:14 +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=1775672714; cv=none; b=QkuHy9ybUS5JI1LNqXrkAhQzuZ2sKlMNN489aH/Prl9RQQvLyAR8hY2bpgV2y6D+HJIlZI83kYfqlC1A2/SLMKNHWbhLfw+fT/KCphgh9BFjyxerHFusj2wF6IO6SEhHRQ5kr3SUQFkf/LUKOF5xNF+eVF/EPGql3n14rSV1Gpk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775672714; c=relaxed/simple; bh=rSjvwX8l8dN8EVpghN1rEpgXDOA78g16N6zqgtZ8ZJ0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=HymFkFKt1l1ARPK6+NhFApvNKXlE9jNt1FbDrWfmmxWLuz3Cn00K4QlWVTbmeHSp1ygKgwQle3aWt4t0SZ36mK1s0S4d1r2gihsS09DwbVPAn2U4OOEPQpS8NE8LA/sTedN849FKS7kgMusTyzCjMY/6J+LcgDhF1czm/PXGpiY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=q7hhxRvw; 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="q7hhxRvw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 710E9C19421; Wed, 8 Apr 2026 18:25:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1775672713; bh=rSjvwX8l8dN8EVpghN1rEpgXDOA78g16N6zqgtZ8ZJ0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=q7hhxRvwGIYf68Fpz1RtwWy1gnRTvJkFHbxCx9El/cB1N56juAe1aIIrC53B+9rVW NWTrwMovR2TSTy4P9a5hlCbj3KB0mEuErjTHT+wnJBKfTsj0Qzr153q9wdMo3QaPtn 4pSct3Ok13dXq1TluFn++UcO5AOzCNkPXC/EHKRo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Miaohe Lin , Thorvald Natvig , Jane Chu , Christian Brauner , Heiko Carstens , Kent Overstreet , "Liam R. Howlett" , Mateusz Guzik , "Matthew Wilcox (Oracle)" , Muchun Song , Oleg Nesterov , Peng Zhang , Tycho Andersen , Andrew Morton , =?UTF-8?q?David=20Nystr=C3=B6m?= , Tugrul Kukul , Alex Williamson , Sasha Levin Subject: [PATCH 6.6 114/160] fork: defer linking file vma until vma is fully initialized Date: Wed, 8 Apr 2026 20:03:21 +0200 Message-ID: <20260408175917.445234207@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260408175913.177092714@linuxfoundation.org> References: <20260408175913.177092714@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Miaohe Lin [ Upstream commit 35e351780fa9d8240dd6f7e4f245f9ea37e96c19 ] Thorvald reported a WARNING [1]. And the root cause is below race: CPU 1 CPU 2 fork hugetlbfs_fallocate dup_mmap hugetlbfs_punch_hole i_mmap_lock_write(mapping); vma_interval_tree_insert_after -- Child vma is visible through i_mmap tree. i_mmap_unlock_write(mapping); hugetlb_dup_vma_private -- Clear vma_lock outside i_mmap_rwsem! i_mmap_lock_write(mapping); hugetlb_vmdelete_list vma_interval_tree_foreach hugetlb_vma_trylock_write -- Vma_lock is cleared. tmp->vm_ops->open -- Alloc new vma_lock outside i_mmap_rwsem! hugetlb_vma_unlock_write -- Vma_lock is assigned!!! i_mmap_unlock_write(mapping); hugetlb_dup_vma_private() and hugetlb_vm_op_open() are called outside i_mmap_rwsem lock while vma lock can be used in the same time. Fix this by deferring linking file vma until vma is fully initialized. Those vmas should be initialized first before they can be used. [tk: Adapted to 6.6 stable where vma_iter_bulk_store() can fail (unlike mainline which uses __mt_dup() for pre-allocation). Preserved error handling via goto fail_nomem_vmi_store. Previous backport (cec11fa2eb512) was reverted (dd782da470761) due to xfstests failures.] Link: https://lkml.kernel.org/r/20240410091441.3539905-1-linmiaohe@huawei.com Fixes: 8d9bfb260814 ("hugetlb: add vma based lock for pmd sharing") Signed-off-by: Miaohe Lin Reported-by: Thorvald Natvig Closes: https://lore.kernel.org/linux-mm/20240129161735.6gmjsswx62o4pbja@revolver/T/ [1] Reviewed-by: Jane Chu Cc: Christian Brauner Cc: Heiko Carstens Cc: Kent Overstreet Cc: Liam R. Howlett Cc: Mateusz Guzik Cc: Matthew Wilcox (Oracle) Cc: Miaohe Lin Cc: Muchun Song Cc: Oleg Nesterov Cc: Peng Zhang Cc: Tycho Andersen Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton Assisted-by: Claude:claude-opus-4.6 Suggested-by: David Nyström Signed-off-by: Tugrul Kukul Acked-by: Alex Williamson Signed-off-by: Sasha Levin --- kernel/fork.c | 29 +++++++++++++++-------------- 1 file changed, 15 insertions(+), 14 deletions(-) diff --git a/kernel/fork.c b/kernel/fork.c index ce6f6e1e39057..5b60692b1a4ea 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -733,6 +733,21 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, } else if (anon_vma_fork(tmp, mpnt)) goto fail_nomem_anon_vma_fork; vm_flags_clear(tmp, VM_LOCKED_MASK); + /* + * Copy/update hugetlb private vma information. + */ + if (is_vm_hugetlb_page(tmp)) + hugetlb_dup_vma_private(tmp); + + /* Link the vma into the MT */ + if (vma_iter_bulk_store(&vmi, tmp)) + goto fail_nomem_vmi_store; + + mm->map_count++; + + if (tmp->vm_ops && tmp->vm_ops->open) + tmp->vm_ops->open(tmp); + file = tmp->vm_file; if (file) { struct address_space *mapping = file->f_mapping; @@ -749,23 +764,9 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, i_mmap_unlock_write(mapping); } - /* - * Copy/update hugetlb private vma information. - */ - if (is_vm_hugetlb_page(tmp)) - hugetlb_dup_vma_private(tmp); - - /* Link the vma into the MT */ - if (vma_iter_bulk_store(&vmi, tmp)) - goto fail_nomem_vmi_store; - - mm->map_count++; if (!(tmp->vm_flags & VM_WIPEONFORK)) retval = copy_page_range(tmp, mpnt); - if (tmp->vm_ops && tmp->vm_ops->open) - tmp->vm_ops->open(tmp); - if (retval) goto loop_out; } -- 2.53.0