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b=qX+LPAe+FZg99nJcTvX6Zs/zpVzkkdM/I6MZvCitoMZUmIAwdsFrU+3fL78cUPkeN ZSpyKFTnbNbxZeVp9BMcStFWr5V3otjSpxy3f1SzH8lo4nR5nYS7G/zbKpqq4zKgKz tidPVU5Y4tmy3RYeoJyiAMkTpMl6VUW1EqI0SK8Z7D7AgE1Xcts1DLpFY3rL/hW6nq mFAVBYXW4OyBgOYIdOCZSGtP48aJa87NBfdeazMz5UqpGAUU1Zbaoq8qHe9/pdCvea rWxIrpT8Svvb38EDIJKdYGhb2J5zA/9/zxY6EQqZtuNEBtDe/0C8sSLII9XWnwlIRa UbKXOItsyA+MQ== Message-ID: Date: Thu, 1 Jan 2026 18:06:23 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [syzbot] [mm?] WARNING in folio_remove_rmap_ptes To: Lorenzo Stoakes , Jeongjun Park Cc: Harry Yoo , Liam.Howlett@oracle.com, akpm@linux-foundation.org, jannh@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, riel@surriel.com, syzbot+b165fc2e11771c66d8ba@syzkaller.appspotmail.com, syzkaller-bugs@googlegroups.com, vbabka@suse.cz References: <20260101130906.839504-1-aha310510@gmail.com> <794095b5-e9ee-4fff-8e3a-1e6b98e670a2@lucifer.local> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: <794095b5-e9ee-4fff-8e3a-1e6b98e670a2@lucifer.local> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 977A4140004 X-Stat-Signature: sxoywyfwjuhti5to6dx1xg55gh8yubfp X-HE-Tag: 1767287190-333116 X-HE-Meta: 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 8KyZfFui UHfGsijFgYa7srYwu3MhJYlO/F6g8VsIYXfaPV535AHmCyeyhJMjmfMlG0m6iH9p4Uau3P6KPq5KVaV9BtbEArhHK1leVLrEXIcFkRdoy7iIgDPPPGIIR4ek/AJx+7yEYxB4uBF7Ep/X51HymBi+AK8UMhjs3/TdaH5D7EOcRP+lgNeSapWarxR/liqolILmW2d7oOjKJpkK1NYcn5Yyy5fgUy4tu+yqcabRw23lSv80dIBayRo82ue3j5P5dJcZHx2ZGGu3CuhWJbh7x9TFRA4ikwITKmp5tUG909Q53KCPo0yPxzMw4RWbRtQSI/TVsq8GVAiNrqxGDO+JAtD0h/jkdf42vaRSh41mfloH8paCDu1kTICVvsIVdCEIoFCRAmxrNOxi/8bd8kUefIDPgq4wc1D0BguFydar3A2SCThPItvbWIZBF/YqHt+z2ZLeR2Jr5 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 1/1/26 17:32, Lorenzo Stoakes wrote: > On Thu, Jan 01, 2026 at 11:30:52PM +0900, Jeongjun Park wrote: >> >> Based on my testing, I found that the WARNING starts from commit >> d23cb648e365 ("mm/mremap: permit mremap() move of multiple VMAs"), >> which is right after commit 2cf442d74216 ("mm/mremap: clean up mlock >> populate behavior") in Lorenzo's mremap-related patch series. > > OK let me take a look. Trying to make sense of the reproducer and how bpf comes into play ... I assume BPF is only used to install a uprobe. We seem to create a file0 and register a uprobe on it. We then mmap() that file with PROT_NONE. We should end up in uprobe_mmap() and trigger a COW fault -> allocate an anon_vma. So likely the bpf magic is only there to allocate an anon_vma for a PROT_NONE region. But it's all a bit confusing ... :) -- Cheers David