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b=Mx3OeGyw4mBMuZbhxP+kZ8Yze1JJTWm6pV1IAfezi4CT5EdyzeaQ4TdJfJEW6VwBl p8EdqXusXxKObgj9b4Q4/xfVD61oTz+Gb23FrCuX4GO8LyEuMBBsTXivo5hQR43jZf Dw65pGexM1LNSYVm+ZFNLaFjxvakbKogJgT96vEI= Date: Sun, 4 Oct 2026 13:07:51 -0700 From: Andrew Morton To: Donggeun Yoo Cc: rppt@kernel.org, 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, kas@kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 0/2] userfaultfd: clear the inherited uffd bit in move_swap_pte() Message-Id: <20261004130751.1cdab825ae521c16e02f66ec@linux-foundation.org> In-Reply-To: <20261003103030.63380-1-donggeunyoo.kernel@gmail.com> References: <20261003103030.63380-1-donggeunyoo.kernel@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 87AAC100003 X-Rspam-User: X-Stat-Signature: rt5wj8qowehyyaakgybab33pw1wqirmm X-HE-Tag: 1791144473-38940 X-HE-Meta: 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 4kbqVhrh L9zOKROj+Qpjf/iRLAVKstSdouKeRH1M6rvb5rQ+kC4HrRiKggUglNoHonmZTfS0YaHo2R/i23A2JyKtRbYPNALRIx1ZqEIkCB1ZxoS5AMarFLQ6smrtBW8XDCdWT0OqtIujIfInOSOKzLiDIecZQzudcvGDkPPoJ/XacrfgbTEfD4NaG67ncRsklG/eNGtTIy6eNX2Bpyq3viTp0+eSFA/3dXVqiw9rUnyvBIsdDTNuCu8HLih5N7417lWg7+IWBXRNZMxMz3FJp6ad+xT4lZ2FoWXZM16IbpMgUVTlXGc+uy+3LFtX6FOd8+XYGeajX42d6XrqhjxccdxAA8hS70PX492q/BhGJZdiXMX8rtPi1wc4sXUw8im20S6KmvU6gwchF38Hb5ISCRF8= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, 3 Oct 2026 19:30:28 +0900 Donggeun Yoo wrote: > 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, and nothing clears it afterwards. Patch 1 clears > the bit, then re-arms it if the destination is RWP-registered, which is > what the present-page and zeropage move paths already do. Patch 2 adds > the tests that catch it. Thanks, I updated mm-hotfixes-unstable with this version. > Changes in v4: > - patch 1: add Acked-by from David Hildenbrand and Mike Rapoport; no > code change > - patch 2: protect the source right after registering it, open pagemap > at the top, and use a designated initializer for the move (David > Hildenbrand) > - patch 2: fail only the test case, not the whole run, when UFFDIO_MOVE > fails (David Hildenbrand) Here's how v4 altered mm.git: tools/testing/selftests/mm/uffd-unit-tests.c | 36 ++++++++--------- 1 file changed, 18 insertions(+), 18 deletions(-) --- a/tools/testing/selftests/mm/uffd-unit-tests.c~b +++ a/tools/testing/selftests/mm/uffd-unit-tests.c @@ -2049,28 +2049,29 @@ static void uffd_move_swap_test_common(u bool rwp) { unsigned long page_size = gopts->page_size; - struct uffdio_move move = { }; - int pagemap_fd; + struct uffdio_move move = { + .dst = (unsigned long)gopts->area_dst, + .src = (unsigned long)gopts->area_src, + .len = page_size, + }; + int pagemap_fd = pagemap_open(); if (rwp) { if (uffd_register_rwp(gopts->uffd, gopts->area_src, page_size)) err("register src failure"); - } else if (uffd_register(gopts->uffd, gopts->area_src, page_size, - false, true, false)) { - err("register src failure"); - } - if (uffd_register(gopts->uffd, gopts->area_dst, page_size, - true, false, false)) - err("register dst failure"); - - if (rwp) rwprotect_range(gopts->uffd, (unsigned long)gopts->area_src, page_size, true); - else + } else { + if (uffd_register(gopts->uffd, gopts->area_src, page_size, + false, true, false)) + err("register src failure"); wp_range(gopts->uffd, (unsigned long)gopts->area_src, page_size, true); + } + if (uffd_register(gopts->uffd, gopts->area_dst, page_size, + true, false, false)) + err("register dst failure"); - pagemap_fd = pagemap_open(); if (madvise(gopts->area_src, page_size, MADV_PAGEOUT)) err("MADV_PAGEOUT"); if (!pagemap_is_swapped(pagemap_fd, gopts->area_src)) { @@ -2078,11 +2079,10 @@ static void uffd_move_swap_test_common(u goto out; } - move.dst = (unsigned long)gopts->area_dst; - move.src = (unsigned long)gopts->area_src; - move.len = page_size; - if (ioctl(gopts->uffd, UFFDIO_MOVE, &move)) - err("UFFDIO_MOVE"); + if (ioctl(gopts->uffd, UFFDIO_MOVE, &move)) { + uffd_test_fail("UFFDIO_MOVE failed: %s", strerror(errno)); + goto out; + } if (pagemap_get_entry(pagemap_fd, gopts->area_dst) & PM_UFFD_WP) uffd_test_fail("uffd bit moved into an area registered for missing faults only"); _