From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 32EA5606A31A for ; Sat, 31 Oct 2026 09:48:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=QoEpOhUZ Received: by kanga.kvack.org (Postfix) id 319816B05E0; Sat, 31 Oct 2026 05:48:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2C1D16B05E1; Sat, 31 Oct 2026 05:48:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 18A046B05E2; Sat, 31 Oct 2026 05:48:22 -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 E73D76B05E0 for ; Sat, 31 Oct 2026 05:48:21 -0400 (EDT) Received: from smtpin17.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 7D76780899 for ; Sat, 31 Oct 2026 09:48:21 +0000 (UTC) X-FDA: 85382446002.17.D25C87C Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf08.hostedemail.com (Postfix) with ESMTP id ADCBD160002 for ; Sat, 31 Oct 2026 09:48:19 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=QoEpOhUZ; spf=pass (imf08.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793440099; b=YBiiDbNPkPeVk8dqnlgy4A+QnhXAiXji40KD34aE4lxL1xDxCX0Ijx7i/MN3aALxjxu1dJ LddupLfxW4SWEetZpkNdkHTVZULy21VZM2qvPIfF1Yd01rISeisfYajIm6siKgw10bucuy BEwQzX+PO/VmY3LaVRV99lh+IqfR2fc= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=QoEpOhUZ; spf=pass (imf08.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@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=1793440099; 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=DxsTnHZLfef+ZwV+bvdRNnaTqozvDnboMuYB5CYD3jE=; b=dc33+D3hBdI6OmTWR/QBn0zAUH3RhxCe7K2RDQlWWzu2DMfys7KjC/Mm0g8yxVQd4dfb+W S4R5WTMRw/uYTyBPWUDIc6EwN8k47KWur/s7Kb9ClyRtplLNKT9mcT6Ucxy1zI+niuDq5D hMwksuu4FMAcGWe5G2kEClmQi3rONMQ= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id EB9B5407F0; Sat, 31 Oct 2026 09:48:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CADAB1F00A18; Sat, 31 Oct 2026 09:48:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793440098; bh=DxsTnHZLfef+ZwV+bvdRNnaTqozvDnboMuYB5CYD3jE=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=QoEpOhUZRVT5ren8mNvEjqn1fyrCuCi3IqzacLFBc1u2HJO2oZExxcKCe19eR+RGQ 8iwI8BvPZqNo5/jrqNSTGGo88w098M0MYwCIhUk6LpVbPz2i7KC/apSep2/KNgnikI CCZGsUUg6SYpN5WNaqgo8h1JdSLlrj3hYY7CzMCHMtG1ewJfyApyunEHXCarGJoL5Y prMZdGWKplHeXSIkx1fzFbYsB0I7gZ7MmULj4BhOGc7AQjO7OtPdPPIl2SKAWZRQVo g2l/0yxLop/YPFutY9Vnr3DZWe2nReOil0JTX8tcvbh73/vuVLd2Z0v/zRvWBDB3E/ ebhBYFeK5WLLQ== From: "David Hildenbrand (Arm)" Date: Sat, 31 Oct 2026 10:40:00 +0100 Subject: [PATCH v3 31/47] mm/mremap: recheck PUDs under the page table lock X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261031-fixes_core-v3-31-d6437171ecc3@kernel.org> References: <20261031-fixes_core-v3-0-d6437171ecc3@kernel.org> In-Reply-To: <20261031-fixes_core-v3-0-d6437171ecc3@kernel.org> To: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, stable@vger.kernel.org, Muhammad Usama Anjum , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2437; i=david@kernel.org; h=from:subject:message-id; bh=YLac1XnofZU1UqgkNCzS2hgJEvURcnZijflAh/9PoUE=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLKebs/M2sG2+2aZx+o8Q2HJ9yX+F78wragxXn+sMS6Ri WfxVTGfjlIWBjEOBlkxRZag4PsGL1+uq61242OGmcPKBDKEgYtTACbyw4vhN4t60MezWt6cQpaK d97fOyKk439i2WG5kKkXGDQZLs+zLWRkWKKb/J/dqOvfq/UKWfytT/oFeqdGrpN5+3lT6H7Tbt3 //AA= X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A X-Rspam-User: X-Rspamd-Queue-Id: ADCBD160002 X-Stat-Signature: poqrc31h7of5p6dey3j378hzan8dxzs8 X-Rspamd-Server: rspam01 X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=4.0.1 X-HE-Tag: 1793440099-667084 X-HE-Meta: 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 uXLYSy8s edtb99DfpVdCN3l2o2l22qgU6OrFj+9ZUhzxQ53H9WQXw6pzZZmMIV6KXlJOC7hlN27oEolczEMnUSRWEuiwDg4j+EojWLwIsb9NqrPqxi8dEViD0f4v5NwLZw8HhwPmkvNJcfIOvzR77RjtQWo3zGkBhn/c/yUPf+joXrEvDnnkGFd187pKn317X0F/Nd5i7yp1E3KFDl0KysdcjHEWo/ok52em1eGX6JLouCEPhd+7Tvkn/44CP6cGCszRvsDZkIIaYG3zCOnlGrucqGOW62V6lv3y8I98oXWfeGMEuHBuE6JLYboPRcEnLCoMy6uSm0xLc4+VaSOh3RLWvLlNP4zCGgXCi94mM76A5qIdvrRwKBT4PbtcpSHzQpfYyM3tqc1Js Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Once get_old_pud() is fixed to accept PUD leaves, unmap_mapping_range() can clear a leaf between the lookup and the move. Holding mmap_lock in write mode does not prevent this. If the zap happens before move_page_tables() tests the entry, an empty PUD can reach move_normal_pud(), where pud_populate() turns it into a present page table entry. If it happens after the test, move_huge_pud() can instead try to move an empty entry, triggering CONFIG_DEBUG_VM warnings on powerpc. Recheck the source under the page table lock in both helpers. Treat an empty source in move_normal_pud() as a completed move, and use __pud_trans_huge_lock() in move_huge_pud(). In the future we should likely have the code lookup a PUD/PMD lockless once, instead of multiple times, because one of the problematic bits here is the: pud_trans_huge(*old_pud) Fixes: 0881ace292b6 ("mm/mremap: use pmd/pud_poplulate to update page table entries") Cc: stable@vger.kernel.org Reviewed-by: Lorenzo Stoakes (ARM) Reviewed-by: Pedro Falcato Tested-by: Muhammad Usama Anjum Signed-off-by: David Hildenbrand (Arm) --- mm/mremap.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/mm/mremap.c b/mm/mremap.c index 16e736c72d9cb..91f0865f6aeea 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -461,14 +461,18 @@ static bool move_normal_pud(struct pagetable_move_control *pmc, if (new_ptl != old_ptl) spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); - /* Clear the pud */ pud = *old_pud; + if (unlikely(pud_none(pud))) + goto out_unlock; + + /* Clear the pud */ pud_clear(old_pud); VM_BUG_ON(!pud_none(*new_pud)); pud_populate(mm, new_pud, pud_pgtable(pud)); flush_tlb_range(vma, pmc->old_addr, pmc->old_addr + PUD_SIZE); +out_unlock: if (new_ptl != old_ptl) spin_unlock(new_ptl); spin_unlock(old_ptl); @@ -503,7 +507,9 @@ static bool move_huge_pud(struct pagetable_move_control *pmc, * We don't have to worry about the ordering of src and dst * ptlocks because exclusive mmap_lock prevents deadlock. */ - old_ptl = pud_lock(mm, old_pud); + old_ptl = __pud_trans_huge_lock(old_pud, vma); + if (unlikely(!old_ptl)) + return false; new_ptl = pud_lockptr(mm, new_pud); if (new_ptl != old_ptl) spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); -- 2.43.0