From nobody Mon Jun 8 07:24:45 2026 Received: from mail-pf1-f172.google.com (mail-pf1-f172.google.com [209.85.210.172]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BB38737C904 for ; Mon, 1 Jun 2026 08:26:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780302378; cv=none; b=UL2Zd2HXKpFdXFa88o3S0HEbUfl96PbxBYnrNNwSIjuELNYUOGfZuyFDMTvi03BXeXQ7md9ciK9miU1ApGk8mO/sR2/+ZhPS/J0zAfONbnSv0dK46TXAb8mxUUm1DVWoO8yTeSMwpVNq9zFTdZzo4lDd8VmScAAlTtz6tepHgq0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780302378; c=relaxed/simple; bh=I7l5HEXjkLQqcLJUntljH+NCuxw9LH3gqEqaYa2IY70=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=qgX+LsOBnHJD2zzO76JuLrmzjh6D5rTHxjF+xxnYIqG2oRJ6GFryv5zOeOaExElvtgVXsDLKICB3iNaXMGX/W6MZoSLVDwwdVvoExlzJ8ODw9hOMq64/fFlKt8KDJ/he22pX90QK4zw7JVhQxZJaIaQm0ayL+tMXFrI8vv7a+Eg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=UPeAO+r5; arc=none smtp.client-ip=209.85.210.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="UPeAO+r5" Received: by mail-pf1-f172.google.com with SMTP id d2e1a72fcca58-84232e83ca9so455678b3a.2 for ; Mon, 01 Jun 2026 01:26:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1780302377; x=1780907177; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=gMscR4W75exckednokoUCQabBPtmF32JAczc6W4udsk=; b=UPeAO+r5BsORkBRXxX77U/+Wpr2PAXlVxbAFtiQgx3ZWj/oCJOex0SFQYVmWPwnjrU j+3WhGXjj50E0Xs1MDfgQovy2MJ4UEfQHa7SrOgIBkrjg2FdwzxaGY74k42I0wk/CMXj Kkj6kICn/lfFDNjf7xU6Z/N/dx0R+aPxgMkLabqkQe2koUwMC7QSEXCfwjC9AmUT8Bq7 e/+CExiGk3jv/NCbYV1SO+k66fN5qGTA6eBzMk2eaEI+vYjvrEWh2aCSP5IdjJF/MW1O WxXLLFjNjq8E6z4UsmFrvsCedOL+74APLUX/9Fo/3N8d+hgr0AvfzVA99srDgY/jj7iK c3ZA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1780302377; x=1780907177; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=gMscR4W75exckednokoUCQabBPtmF32JAczc6W4udsk=; b=k3qr06snn4FguGet8kvIHoI2mElV8mtFk/DlJAeZ4CRDs6pLwFe875zi9Le4lfpiUT 10K8byWYAIxhsmOmFmVa00KeUy+znsfaw+qRReSxvXB7VwrCc4n+rRMxLzrXFmIOmLdt U4qKKuTHCBA0iqTZAqfSnJgxDWudHVEkO2ocjbZuU369dk+37BiD8KSHk8BUozOSjR3I bmklvM9bwkBkKDo98KGvEoIv+b/4D6qB3h3QCf5VytN7hHLEIAaZU3Y/I6cxTb/ua7WY F1ElX30Fu8lQKH9a3JFRc8c5K+Q/H4GR1pD4eY/G97bChqGrVcNwVFjamXe+YLE2JL17 B5kQ== X-Forwarded-Encrypted: i=1; AFNElJ/HMTxhYYOUFwCN8iApYfe3IwZS896mdHTPEr2GFMY8KQwf9chwc96/s44gIvntrFBO05mahfK1W0cD0Z8=@vger.kernel.org X-Gm-Message-State: AOJu0YwXzbXHHAy3Rth3MDLsR5XMWcpKS6OgELL2+gRCyRNa11hXkmUE vW3JI8X9eZRQcMgMorwVXJD5Yn3M2X8b2zSSvXRZdz6qEyKMYTKOwJPy5xWFUg== X-Gm-Gg: Acq92OFlPrQfDATjmED+fYnU4+lFBnvBEd+ZTObXr+QsT/scb49QKBWgCSXXLN+EB25 d2bpfJi8+/5FrwHN02QpISuu4BpRM120ayrJn4ExHJqWpmh/ySrT/R5UCFtEumPXgez5PFwFVrz V/wbbxW261P3yXyDFmJqotetegRyMEDJiG8n5tLH2hbzx5ItpJgvRYLJxuUIb+XxEaXjrTXyrem yj3+u9WLXXtqiRDa3xTDHZL8Gbj9LK5Svx7syik9JLsuZaifI5JSgYXyZl6MbOZgzGHkLaUWtZ/ JKl3640X9SxgM7DhLmnEE0xMsw4lZByMqB2joVVqj+4Bw7REyVDgySbKMPKVNISvmsiDo/4+B4a qXmjpOb5smX02/5rlt7cZkPdvyqIpaieZRjgL3JYY5i1AZqhCDVbAxua2gGlYsWvpfszLTlqNmS 8pzbdKO7gQ1IDtvsrWzS++TK8eBwYBkn9absbXNQI8cr/kL327evi6TkkpzA== X-Received: by 2002:a05:6a00:2987:b0:82f:4191:da10 with SMTP id d2e1a72fcca58-84225385e77mr8973517b3a.6.1780302376382; Mon, 01 Jun 2026 01:26:16 -0700 (PDT) Received: from zjh-os.zhaoxin.com ([104.249.174.136]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-84214d018fcsm9030049b3a.60.2026.06.01.01.26.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Jun 2026 01:26:16 -0700 (PDT) From: Jianhui Zhou To: akpm@linux-foundation.org, rppt@kernel.org, linux-mm@kvack.org Cc: peterx@redhat.com, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, syzbot+18d274a59b87cf80e86d@syzkaller.appspotmail.com, Jianhui Zhou Subject: [PATCH] mm/userfaultfd: clear uffd-wp PTE state when re-registering without WP Date: Mon, 1 Jun 2026 16:26:09 +0800 Message-ID: <20260601082609.170076-1-jianhuizzzzz@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" UFFDIO_REGISTER can be issued on a range that is already registered in the same userfaultfd context, replacing the VMA's userfaultfd tracking mode. For example, a range can be registered with UFFDIO_REGISTER_MODE_WP and later re-registered with UFFDIO_REGISTER_MODE_MISSING. When the second registration removes VM_UFFD_WP, the VMA flags are updated but existing uffd-wp state in page-table entries is left behind. That stale state can survive in swap PTEs. On swapin, do_swap_page() restores _PAGE_UFFD_WP from the swap PTE and can then install a writable PTE, triggering page_table_check: pte_uffd_wp(pte) && pte_write(pte) Handle removal of WP mode through UFFDIO_REGISTER the same way as UFFDIO_UNREGISTER: resolve the per-PTE uffd-wp state before dropping VM_UFFD_WP from the VMA. Also make the same-context fast path require an exact UFFD mode match. The old subset check treats MISSING|WP -> MISSING as a no-op, even though WP mode is being removed. Fixes: f45ec5ff16a7 ("userfaultfd: wp: support swap and page migration") Reported-by: syzbot+18d274a59b87cf80e86d@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D18d274a59b87cf80e86d Signed-off-by: Jianhui Zhou --- mm/userfaultfd.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 180bad42fc79..dc0b3eba768b 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -2153,13 +2153,21 @@ int userfaultfd_register_range(struct userfaultfd_c= tx *ctx, * userfaultfd and with the right tracking mode too. */ if (vma->vm_userfaultfd_ctx.ctx =3D=3D ctx && - vma_test_all_mask(vma, vma_flags)) + (vma->vm_flags & __VM_UFFD_FLAGS) =3D=3D vm_flags) goto skip; =20 if (vma->vm_start > start) start =3D vma->vm_start; vma_end =3D min(end, vma->vm_end); =20 + /* + * Re-registering into the same userfaultfd can remove WP mode. + * Clear any per-PTE uffd-wp state before dropping VM_UFFD_WP, + * matching the UFFDIO_UNREGISTER cleanup semantics. + */ + if (userfaultfd_wp(vma) && !(vm_flags & VM_UFFD_WP)) + uffd_wp_range(vma, start, vma_end - start, false); + new_vma_flags =3D vma->flags; vma_flags_clear_mask(&new_vma_flags, __VMA_UFFD_FLAGS); vma_flags_set_mask(&new_vma_flags, vma_flags); base-commit: e43ffb69e0438cddd72aaa30898b4dc446f664f8 --=20 2.43.0