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Howlett" , Harry Yoo , Alistair Popple , Baolin Wang , Barry Song , Byungchul Park , Gregory Price , "Huang, Ying" , Jann Horn , Joshua Hahn , Mariano Pache , Mathew Brost , Peter Xu , Rakie Kim , Rik van Riel , Ryan Roberts , Usama Arif , Vlastimil Babka , Yu Zhao , Andrew Morton References: <2025101627-shortage-author-7f5b@gregkh> <20251017085106.16330-1-lance.yang@linux.dev> <121d5933-16d9-4eb5-b2b5-2edff9b36c16@lucifer.local> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: <121d5933-16d9-4eb5-b2b5-2edff9b36c16@lucifer.local> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: orgo7haa5ndwgu66tp97w6wqyfek7ndz X-Rspamd-Queue-Id: ADBFA20016 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1760696755-283326 X-HE-Meta: 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 VnqPuDxS k7TCYTMdPNMhyPxR2912kZvCvV4YKvpR08QTXJ+Ka0lzTJoE7geah9kZ8X3bKw2D7vXtXX4+0/63zBZSZMVXRUc9Ga1kIn7dJ1RvXPAyZjaQ507ADtuOJpK3CVgWsjiY9ypb9l0lTKxU+Q6EwpONILTFstCovkds2RcJElONn/u3kBN+oZUbh//Wl26t4/JwoHr0nWhSrPh//xoqN9+fwDthIW2TxsU8L8+r3M0HIwRybvtyxVKo7/k9sLub1sYiw8tL/QuatOn5FFUVTCkkv/MNMjSq90zSgn1s/wUqB+5OhYf7Sy8lqxeGCA5sAqf+7rkpoXFeNUD26Yyw0eNdL3myYy+uEu4vHOTKVtybNEpd/RwkWqGc78dxt3TCapFl2W3r2st5InRyUmmpRDR9SOPj+nxGPV2O1BnJzvbvu4KFu9gXTM8RGfmUd+g== 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 2025/10/17 17:52, Lorenzo Stoakes wrote: > On Fri, Oct 17, 2025 at 04:51:06PM +0800, Lance Yang wrote: >> From: Lance Yang >> >> When splitting an mTHP and replacing a zero-filled subpage with the shared >> zeropage, try_to_map_unused_to_zeropage() currently drops several >> important PTE bits. >> >> For userspace tools like CRIU, which rely on the soft-dirty mechanism for >> incremental snapshots, losing the soft-dirty bit means modified pages are >> missed, leading to inconsistent memory state after restore. >> >> As pointed out by David, the more critical uffd-wp bit is also dropped. >> This breaks the userfaultfd write-protection mechanism, causing writes to >> be silently missed by monitoring applications, which can lead to data >> corruption. >> >> Preserve both the soft-dirty and uffd-wp bits from the old PTE when >> creating the new zeropage mapping to ensure they are correctly tracked. >> >> Link: https://lkml.kernel.org/r/20250930081040.80926-1-lance.yang@linux.dev >> Fixes: b1f202060afe ("mm: remap unused subpages to shared zeropage when splitting isolated thp") >> Signed-off-by: Lance Yang >> Suggested-by: David Hildenbrand >> Suggested-by: Dev Jain >> Acked-by: David Hildenbrand >> Reviewed-by: Dev Jain >> Acked-by: Zi Yan >> Reviewed-by: Liam R. Howlett >> Reviewed-by: Harry Yoo > > You're missing my R-b... Sorry, I missed it! I just cherry-picked the commit from upstream and didn't notice ... Hopefully Greg can add your Reviewed-by when applying.