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[99.254.114.190]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6dfad9adf79sm68242536d6.51.2025.01.15.12.28.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Jan 2025 12:28:02 -0800 (PST) Date: Wed, 15 Jan 2025 15:28:00 -0500 From: Peter Xu To: Ryan Roberts Cc: Andrew Morton , Muchun Song , "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Shuah Khan , David Hildenbrand , =?utf-8?Q?Miko=C5=82aj?= Lenczewski , Mark Rutland , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v1 1/2] mm: Clear uffd-wp PTE/PMD state on mremap() Message-ID: References: <20250107144755.1871363-1-ryan.roberts@arm.com> <20250107144755.1871363-2-ryan.roberts@arm.com> MIME-Version: 1.0 In-Reply-To: <20250107144755.1871363-2-ryan.roberts@arm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: xWhk-t4vCmbdgAsvceRecd06XoUWxviONOjXmbC07QY_1736972884 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit X-Stat-Signature: atjqsn5tyfr9mxkox5sr8k5j1opk3cqa X-Rspam-User: X-Rspamd-Queue-Id: C0C6A4000B X-Rspamd-Server: rspam03 X-HE-Tag: 1736972890-722102 X-HE-Meta: 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 PjslgLCD 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jan 07, 2025 at 02:47:52PM +0000, Ryan Roberts wrote: > When mremap()ing a memory region previously registered with userfaultfd > as write-protected but without UFFD_FEATURE_EVENT_REMAP, an > inconsistency in flag clearing leads to a mismatch between the vma flags > (which have uffd-wp cleared) and the pte/pmd flags (which do not have > uffd-wp cleared). This mismatch causes a subsequent mprotect(PROT_WRITE) > to trigger a warning in page_table_check_pte_flags() due to setting the > pte to writable while uffd-wp is still set. > > Fix this by always explicitly clearing the uffd-wp pte/pmd flags on any > such mremap() so that the values are consistent with the existing > clearing of VM_UFFD_WP. Be careful to clear the logical flag regardless > of its physical form; a PTE bit, a swap PTE bit, or a PTE marker. Cover > PTE, huge PMD and hugetlb paths. > > Co-developed-by: Mikołaj Lenczewski > Signed-off-by: Mikołaj Lenczewski > Signed-off-by: Ryan Roberts > Closes: https://lore.kernel.org/linux-mm/810b44a8-d2ae-4107-b665-5a42eae2d948@arm.com/ > Fixes: 63b2d4174c4a ("userfaultfd: wp: add the writeprotect API to userfaultfd ioctl") > Cc: stable@vger.kernel.org Nothing I see wrong: Reviewed-by: Peter Xu One trivial thing: some multiple-line comments is following the net/ coding style rather than mm/, but well.. I don't think it's a huge deal. https://www.kernel.org/doc/html/v4.10/process/coding-style.html#commenting Thanks again. -- Peter Xu