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=1794590454; b=JooOBuMSwB0yW4IBuYGC8BDOyu5U0ElEJsWjI7qcQ9lQvaqFcP6fPlxt3XLvyutyT8IG Sm9OgNeoKvxmF8QPYEDOjvzsA182BBUAv2HHDGoiVnd78XCne1gRSYdBUtkIkO5rb8X9v 3RQQcrbnvIkpi0icG7EPZQPwwsm2F0Z78wqlNi/RHSEpgCKqbwjjQPPPpqa5Ni05unXeh PKS6Os1keDKpvZLeAWCKgLlKTzkM3rO2LNPkW96Ls4OUetEArOn1dC7w4en8xQHZsdmUB LV/TBkCsxxHQghGQ4GYBIQl9fTsMSkvFOtjuuykALl62wLjGO/03ztPFjunQrraGjOw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794590454; 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=++r+SxO9zXor3VbRXp0HtghnkTbiLpvP637OKXrIgcA=; b=QnauWV0wctpEs1qaG7rdl7BVUvvHW7BOYIjJW9g4WGLyjhdcULhilViVzKm0+6jEO35W yh+CyRcoIDqKy1VVR1JoTJMWRvilCYi/WvMvjcwHugPOyNyAXTEwsxA6DlU2+efUy3/6O nHSG2kKhQNabiIpJyvxyUsoryt7Dk6NnNjJlA9/cSRPG6/KJqa+pEK+qMKWiFZjN8FnDD eWRL9DuXH1fun/9lU6EGVAHopBvwX0RXwQAHyctJCBe5SX3XXYCEgk2TZTaZpW3zUGBDX l2cDcd0t+lg85j4JAHTvczEH1woSXGVez2+vNBsBMbk9WX6pCNPHxXAhRnW5UtdEr+g== 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=rF62tlkL; 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 EE2B46070F3C; Fri, 13 Nov 2026 17:20:53 +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=rF62tlkL Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9A4FD1F000C7; Fri, 13 Nov 2026 17:20:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794590453; bh=++r+SxO9zXor3VbRXp0HtghnkTbiLpvP637OKXrIgcA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=rF62tlkL486qXlsqDNALSwwBN5p+46feIP3/tNHeISkNvNbWtgDmUAKfXA4BuhONJ pI91c/GYnp0msbpOqSj4V9mgi7GJ/uVRVci47xLR1TTqg2MIRkkB4mYG3UR+JWvOnz QH1eaECoZDIDQahPvzTm/68H67GpnrMB6pO1ZCts= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Josef Bacik , "Gregory Price (Meta)" , Muhammad Usama Anjum , Lance Yang , Baolin Wang , "David Hildenbrand (Arm)" , Sasha Levin Subject: [PATCH 6.18 369/686] mm/khugepaged: always recheck the pmd in try_collapse_pte_mapped_thp() Date: Fri, 13 Nov 2026 10:48:22 -0500 Message-ID: <20261113153833.423688321@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: stable@vger.kernel.org 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: Josef Bacik [ Upstream commit aa72cf34d90da7019591ab67533a8ece8b41da2d ] try_collapse_pte_mapped_thp() drops the PTE lock after it has cleared the page table, and takes the PMD lock and the PTE lock to remove it. In between, MADV_DONTNEED with CONFIG_PT_RECLAIM can reclaim the page table. The pmd_same() check is supposed to handle this, but it is only done with CONFIG_SPLIT_PTE_PTLOCKS. Fix it by performing the check unconditionally. Fix generated by an LLM and sent by Josef Bacik in private. Fixes: 6375e95f381e ("mm: pgtable: reclaim empty PTE page in madvise(MADV_DONTNEED)") Cc: stable@vger.kernel.org Signed-off-by: Josef Bacik [ david: adjust description ] Reviewed-by: Gregory Price (Meta) Tested-by: Gregory Price (Meta) Tested-by: Muhammad Usama Anjum Link: https://patch.msgid.link/20261031-fixes_core-v3-15-d6437171ecc3@kernel.org Reviewed-by: Lance Yang Reviewed-by: Baolin Wang Signed-off-by: David Hildenbrand (Arm) Signed-off-by: Sasha Levin --- mm/khugepaged.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 8ed9b2a3e8f07..573e4063eaf60 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1664,12 +1664,11 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr, /* step 4: remove empty page table */ if (!pml) { pml = pmd_lock(mm, pmd); - if (ptl != pml) { + if (ptl != pml) spin_lock_nested(ptl, SINGLE_DEPTH_NESTING); - if (unlikely(!pmd_same(pgt_pmd, pmdp_get_lockless(pmd)))) { - flush_tlb_mm(mm); - goto unlock; - } + if (unlikely(!pmd_same(pgt_pmd, pmdp_get_lockless(pmd)))) { + flush_tlb_mm(mm); + goto unlock; } } pgt_pmd = pmdp_collapse_flush(vma, haddr, pmd); -- 2.53.0