From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 29FA817B505 for ; Mon, 10 Aug 2026 10:58:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786359495; cv=none; b=dYBQqMvG16YAd9o6Fix4J8ZjYOWpqgAN+4cq29qp1mw3KdnM/9OfgKhnl5OP7l37IrJgJKLCMs6Sb5xg2MUQl5Sgb6lmtXpF7+h0jTGlJmmJnp6mtNL5IP7ai5rIO/hTgFpcXPfNCIXgdvyydUn6enLQGxUaEua148LfNCcZYm0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786359495; c=relaxed/simple; bh=tjlS5pxnpCmgr6Gl9LYsPP06yNaghR9WwkpXQjjQ7Kk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=j28J8batErTBzQb9x6kajs2aypthuUP92+UUn9tghIfcy5pnuyd/UIW909JX+5PCqxXFykxPfSLuZxKxooi6IZa858zXoNAGoD6SNTsttRfGvRnjb645VSlzBIsITP70OpiQDR5j8lBCl5tPlfoW+4pVliAXTOa1imNdlDbh38I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=b5ejBUY8; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="b5ejBUY8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1116E1F00A3D; Mon, 10 Aug 2026 10:58:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786359493; bh=KdotRg4ENitzP0Ir6Ebm/nE6WXUDmGoDBFc4caAU0Jw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=b5ejBUY8knbuH+c6O1XEx15dUsrbUWb1qwGjznWAznMpQ99NM71VojO3UmVSUgQFb lyA6YzVT17AOML11J7PzKZMgPTDwiFU9vvhVdwUgqPIQRU4vY5+x9X32H6xBbqf7WV lBoHHFFV+r8xqNBi3oRXM2zcSf6hX7GEdGWtNQBdZ3xFMPNAyYhiicypzrUBuDEgh1 QLgnXgz8Rf9QLCMrzOPtMbuHAQilO5mkXoRpI6kc3lEpeRVDSIpQuguZW8/GH9BcdB +805nRzgZ4jbmkABqwGIX8L9toQxoRJ90Z6b1g01CZWTRrq0h0yuVOoInQJdnFipbX fNkBC/yoexP1w== From: Sasha Levin To: stable@vger.kernel.org Cc: Usama Arif , sashiko-bot , Rik van Riel , Baolin Wang , Lance Yang , "David Hildenbrand (Arm)" , Lorenzo Stoakes , Andrea Arcangeli , Barry Song , Dev Jain , Johannes Weiner , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Shakeel Butt , Zi Yan , Andrew Morton , Sasha Levin Subject: [PATCH 6.18.y 3/3] userfaultfd: wait on source PMD during UFFDIO_MOVE Date: Mon, 10 Aug 2026 06:57:55 -0400 Message-ID: <20260810105755.579268-3-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260810105755.579268-1-sashal@kernel.org> References: <2026080544-exit-cesarean-7929@gregkh> <20260810105755.579268-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Usama Arif [ Upstream commit 4165b7d1c45c2da0dfefe528f8d1fb7d79f0d344 ] move_pages_huge_pmd() snapshots src_pmdval under src_ptl, drops the lock, and, for migration entries, waits with pmd_migration_entry_wait(). Passing &src_pmdval is wrong. pmd_migration_entry_wait() must lock and re-read the real page-table PMD; on split-PMD-lock kernels, a stack address also resolves to the wrong lock. softleaf_entry_wait_on_locked() then waits without a folio reference, which is safe only while serialized against migration-entry removal by the real PT lock. Pass src_pmd, matching __handle_mm_fault() and hmm_vma_walk_pmd(). Link: https://lore.kernel.org/20260705131231.1499198-1-usama.arif@linux.dev Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI") Reported-by: sashiko-bot Link: https://sashiko.dev/#/patchset/20260703173903.3789516-1-usama.arif%40linux.dev?part=8 Signed-off-by: Usama Arif Reviewed-by: Rik van Riel Reviewed-by: Baolin Wang Reviewed-by: Lance Yang Acked-by: David Hildenbrand (Arm) Reviewed-by: Lance Yang Reviewed-by: Lorenzo Stoakes Cc: Andrea Arcangeli Cc: Barry Song Cc: Dev Jain Cc: Johannes Weiner Cc: Liam R. Howlett Cc: Nico Pache Cc: Ryan Roberts Cc: Shakeel Butt Cc: Zi Yan Cc: Signed-off-by: Andrew Morton Signed-off-by: Sasha Levin --- mm/huge_memory.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 3e72672b19c69..00f99ec85d8a1 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2560,7 +2560,7 @@ int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pm if (!pmd_trans_huge(src_pmdval)) { spin_unlock(src_ptl); if (pmd_is_migration_entry(src_pmdval)) { - pmd_migration_entry_wait(mm, &src_pmdval); + pmd_migration_entry_wait(mm, src_pmd); return -EAGAIN; } return -ENOENT; -- 2.53.0