From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D8EB8C98328 for ; Sat, 26 Sep 2026 12:42:01 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D5E936B008C; Sat, 26 Sep 2026 08:42:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D08D86B0092; Sat, 26 Sep 2026 08:42:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C1E256B0093; Sat, 26 Sep 2026 08:42:00 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 8D6986B008C for ; Sat, 26 Sep 2026 08:42:00 -0400 (EDT) Received: from smtpin26.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 1EE25120899 for ; Sat, 26 Sep 2026 12:42:00 +0000 (UTC) X-FDA: 85255875600.26.872BA87 Received: from mail-pj2-f40.google.com (mail-pj2-f40.google.com [74.125.227.168]) by imf29.hostedemail.com (Postfix) with ESMTP id 5BCE8120005 for ; Sat, 26 Sep 2026 12:41:58 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=gmail.com header.s=20251104 header.b=OGCd3kyC; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf29.hostedemail.com: domain of donggeunyoo.kernel@gmail.com designates 74.125.227.168 as permitted sender) smtp.mailfrom=donggeunyoo.kernel@gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1790426518; 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-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=YxUX0NroNmM2djP5qsrTpM2pYvDo5f/LrOtTkWteY6U=; b=0ajzLbAcgf8jfAgJfywFUHXIskjJ/0pAb4QJiRVWy4/SNeECAVESJnXAffCI1DX7Jh1A0Y vE7bzTQlJ07wKcqXOLRtpJrA5hZ1BUj+NSxFK/Ps5L7440uAnoEc+o1Mp6vDYH4bckwdX6 DVc8oNP9I2b0IKISOrFTFjDD0iTyv0Y= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=gmail.com header.s=20251104 header.b=OGCd3kyC; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf29.hostedemail.com: domain of donggeunyoo.kernel@gmail.com designates 74.125.227.168 as permitted sender) smtp.mailfrom=donggeunyoo.kernel@gmail.com ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1790426518; b=GaFOScQTwoPnnk2QyAMJ9yaJbFMX0+r2aYQlHBmqYW+1HcletKJdGa3TkXOUtB1OHc3pvb Og9uxfpFyVotGXyUnCfbtSQliRIW1oaTZUI13bfHij5jMn4LjjIrXE7Fa/HEXWAe5/cb9E eN3FSpn2l9FAFC9le5Txe5ip74CxmJw= Received: by mail-pj2-f40.google.com with SMTP id 98e67ed59e1d1-3a0dc47fee0so230620a91.1 for ; Sat, 26 Sep 2026 05:41:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1790426517; x=1791031317; darn=kvack.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=YxUX0NroNmM2djP5qsrTpM2pYvDo5f/LrOtTkWteY6U=; b=OGCd3kyCj/xQYf8BpwNiBx6FD1lNkihNaxC7R8P37xX4AiH1+A9m6Hg6UjVVgfQlEr kOPI+pMVRVPH1zpyiGpvO4u/CYT6uh+3UgKxK7jVG/boLW5cgmYS3j2YWVhagK6BCnaH oDyAofIkAQ9kB4bS/kifgCNRZi69NMf3CS69xMn/0XUo89bDHJhM1OHKk7O8VPRbGQut O2wOBEg/UoOkXCq6MnVG05gqk4lnRnSaao1XdVHRvve1jK0b5mszmmbgFiRUYM4hZi+l Js5VPvoDZjnnOwQiyIdy9UprAEJgWDQMIpi4ynnaaxg1M003GPLIYPLo1VOJekjzarWk Hn+Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790426517; x=1791031317; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=YxUX0NroNmM2djP5qsrTpM2pYvDo5f/LrOtTkWteY6U=; b=BletsfLd8iYXjdZAwVF7s3EjqceUTeCsL+LmVV9behhMUG7eClQ/o/qC3uVOiCfjYC 6JUIY+lCxNQ46J2Gppm1D7QBpQqrg/O0BOdttRymi5WN9h+wRlS4W4K3jhjGGHZaKVgV mELRBtgYScNM88nj/W3TJNImHxLkKAjNA/1uK+jLIE5f3dQTLiek6eFL6fNDtwf5lDYL KkGRVI0XlVTHk7QXuL4PW0shzom59d5ik0r6K8zuDC0m93gScUEFto713wC5T0MmiuDN uYXPYJReaARwYkMiQ1vpZPmzc9y8/ws+z6mqHGEDiTldoA1pZsOMejxLgqCde09j3Uyg BIIQ== X-Forwarded-Encrypted: i=1; AKwUvBxcgc7GCPXt0JpoeEjF8Wrj2tR9t5dOUby+cxB4AjI0twKPidowTFBwezpkD4fnjnlAitYWcrCZ8A==@kvack.org X-Gm-Message-State: AFq9FYLb4fDwVI7wnwvOQeakn0dmxysdqz8yWIs7n5IqHWVSvDoScZzJ 31wmEfsXQCOy4iGtcL4vL+lkwXbkrLjQC79BofhRIpVMXJKJ4nfoW/rRIu1CrEEPKA== X-Gm-Gg: AYBFou2QGqZVEl8C64tZKIvOlAUAjnomFVESC7yI6sM3rexhP0fiaYr4GpVvAbm1olI tWeyncvYCf9eD8Pzp0o6Tfh3ey+6RtabsQGKZZh7nUT9DGHbnsDaJmVrTXcRb1zzZ4nqdPLjh/j z6kggDE2EOvjo/OsHhc5Xr3P2sFpoauQly5b3rWrTpcsjy5Bms0Um1cwsh5A9fBN509NbPZTCsh MAbPY0y9GFIjIoCgbYAHekmqljjpTOllfwakwyTRymC+zyjotEken3zICZycJdPnqFvt48UI/Mc n+1irvHEyeMdScLjJNJTxA1BBkB7X4giuMge3yfg5PSzp29V1QWDODe5NSeFu+IVx3aTenE8uyL f1J49ern7jXXcyhEXTvSYqgUl8Xb4EXpZbxz8P4CctocRiPqucz+tYxv/+Elf9qVo4QDzhUAvXe W/AZuUoPztSnpGpqEc9KvTKj8R3ngcnmRCSClxF5ubJDCfOR4qPNoelkcnxah0Ea02JJBFkDzfp Q2zkBxZL6Zq/CkbO3klPhkF3RqTJ7wTs4k= X-Received: by 2002:a17:90b:1a8a:b0:3a0:cb48:df68 with SMTP id 98e67ed59e1d1-3a0cb48e2afmr3146943a91.13.1790426517221; Sat, 26 Sep 2026 05:41:57 -0700 (PDT) Received: from ydg-Zenbook-14-UM3406GA ([211.230.25.193]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a0cd1c4ec9sm5965212a91.16.2026.09.26.05.41.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 26 Sep 2026 05:41:56 -0700 (PDT) From: Donggeun Yoo To: akpm@linux-foundation.org, rppt@kernel.org Cc: peterx@redhat.com, surenb@google.com, aarcange@redhat.com, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, mhocko@suse.com, shuah@kernel.org, kirill@shutemov.name, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, donggeunyoo.kernel@gmail.com, stable@vger.kernel.org Subject: [PATCH v3 1/2] userfaultfd: clear the inherited uffd bit in move_swap_pte() Date: Sat, 26 Sep 2026 21:41:44 +0900 Message-ID: <20260926124145.2878520-2-donggeunyoo.kernel@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260926124145.2878520-1-donggeunyoo.kernel@gmail.com> References: <20260926124145.2878520-1-donggeunyoo.kernel@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: zdnetnyxmcmarcb1ta4dp9srd93a5fef X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 5BCE8120005 X-HE-Tag: 1790426518-439938 X-HE-Meta: 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 A9a5hIdG 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: UFFDIO_MOVE on a swapped-out page installs the source PTE at the destination unchanged, so a uffd bit set on a write-protected or RWP-protected source lands in a destination VMA that was never registered for either. Nothing clears it there, and userspace sees: - /proc//pagemap reports the page as uffd-tracked (bit 57), both while it is swapped out and after it is faulted back in. - MADV_COLLAPSE fails with EINVAL on a range containing it, because the collapse scan bails on a swap entry with the uffd bit set. - With CONFIG_PAGE_TABLE_CHECK, faulting the page in warns. do_swap_page() carries the bit into the present PTE and, since the destination isn't WP-registered, also makes it writable: WARNING: mm/page_table_check.c:202 at __page_table_check_ptes_set+0x185/0x1e0 Call Trace: set_ptes+0x67/0xc0 do_swap_page+0x990/0xfe0 __handle_mm_fault+0x7d0/0xeb0 handle_mm_fault+0x9c/0x250 do_user_addr_fault+0x207/0x650 exc_page_fault+0x65/0x150 asm_exc_page_fault+0x26/0x30 Reaching it takes UFFDIO_MOVE out of a WP- or RWP-protected area into one that isn't, on a page that is swapped out at the time. It hasn't been seen in practice. A resident page doesn't carry the bit, because move_present_ptes() builds the destination PTE from dst_vma->vm_page_prot. Clear it on the moved swap entry as well, then re-arm it if the destination is RWP-registered. The WP case has been there since v6.8, where UFFDIO_MOVE was added. Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI") Cc: Assisted-by: LLM Signed-off-by: Donggeun Yoo --- mm/userfaultfd.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 74f04c323c50f..f39f109f17989 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -1449,6 +1449,7 @@ static int move_swap_pte(struct mm_struct *mm, struct vm_area_struct *dst_vma, orig_src_pte = ptep_get_and_clear(mm, src_addr, src_pte); if (pgtable_supports_soft_dirty()) orig_src_pte = pte_swp_mksoft_dirty(orig_src_pte); + orig_src_pte = pte_swp_clear_uffd(orig_src_pte); /* Re-arm RWP on the moved swap entry if dst_vma is RWP-registered. */ if (userfaultfd_rwp(dst_vma)) orig_src_pte = pte_swp_mkuffd(orig_src_pte); -- 2.53.0