From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794590414; b=B0/IyMXwEkfoXiTDpTgKy/aUlr+QZlvK6znedXg0MhHKc9XGTmNDIt1CCSmqqcXlKJ+e t/DADQ0do2MFoScSQbsYvysBxRvnPqqqtZZJoNTFwYRBmwuwXIkt0Zl2XJGxi73bN8j1W myVJHCL33tZsSdbRBxMptgjjM4Ll4J47NZw8UIYUceSQgWkwCMkdJ9LCuojG2xMhJusBO YfkEdOZiyCtH0C+cNdvTjVp3Y9VOv56RGa8eMNSRto97y5ziIM5SxkysNbV46oOp+R6QI VPI0wpd3n2XU/yJK0ny2p9sH3QhH7wZWpWY2JGwq5QcrIcc3mtWUgIHvlAoano2bbNQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794590414; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=vo8EZQnxxxQCInbVsQRSw15zky5zFIvamxv9n10//8s=; b=2GYOptUQAWMGERgx0pPqWyTf3GEjHjPnie3S74iWAIEedzsHmGYwRB5NIvVA92UJlMie 3NaIRnut+9PqbJi508v3ZRB3Waz191lZLc+Y1cjiri9mv/HDBLmEMowThhJen1yH5N18o Bd6MlMtmzgdWMssdHfz7/n3H79cH5Dfz8lcPBlvJCKtNIWaP/AYt1p3bQr5HTp1RCKB7T /HFNmmNdMwmDMVvJEVVYcNORhhcdQ8VZN0llLvf/QPCDdd2XSIp9NokOzFR1uA/XqtF9p h8RTkzsTJkMD+l5/seTNZkpAtUXi/nZF+orPXzsMri9czpXvtpr37MiEHNZIoXXE0pA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=qNJevJm6; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 885B5606A8A2; Fri, 13 Nov 2026 17:20:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=qNJevJm6 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3A4AD1F000C6; Fri, 13 Nov 2026 17:20:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794590414; bh=vo8EZQnxxxQCInbVsQRSw15zky5zFIvamxv9n10//8s=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=qNJevJm6fekrJt6GtjKiTx2jFRtAKOgM9QRiLSjzJyqALOW23YPPDfMSom+7RI8q2 lYBlyS2zz5mmS27iMbXqSjOvPyB5IfpcDqzGoOIU0d/GtA0uL4S8+SuGMk5Ud1uSl+ yhwasiQkwt/72nNplqseXbu9+rduXXwpYBHVqsYU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Lorenzo Stoakes (ARM)" , Pedro Falcato , Muhammad Usama Anjum , Lance Yang , "David Hildenbrand (Arm)" , Sasha Levin Subject: [PATCH 6.18 380/686] mm/mremap: recheck PUDs under the page table lock Date: Fri, 13 Nov 2026 10:48:33 -0500 Message-ID: <20261113153833.799773016@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153820.902362109@linuxfoundation.org> References: <20261113153820.902362109@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Hildenbrand (Arm) [ Upstream commit 402882943dfa8bab5c2bcc66189f9fb2828f248e ] 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 Link: https://patch.msgid.link/20261031-fixes_core-v3-31-d6437171ecc3@kernel.org Reviewed-by: Lance Yang Signed-off-by: David Hildenbrand (Arm) Signed-off-by: Sasha Levin --- mm/mremap.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/mm/mremap.c b/mm/mremap.c index 1830ecb91e3c1..369e1406854d3 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -448,14 +448,18 @@ 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); @@ -490,7 +494,9 @@ 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); -- 2.53.0