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Thu, 09 Apr 2026 23:51:40 -0700 (PDT) MIME-Version: 1.0 References: <20260409103345.15044-1-komlomal@gmail.com> In-Reply-To: From: "Denis M. Karpov" Date: Fri, 10 Apr 2026 09:51:28 +0300 X-Gm-Features: AQROBzBbYnfPywRG3Yp0tRYc7KAWWajkBK8MVh_qYfBGHCI1-FaAx9kMSaKpQ04 Message-ID: Subject: Re: [PATCH v2] userfaultfd: allow registration of ranges below mmap_min_addr To: "Liam R. Howlett" , "Denis M. Karpov" , Mike Rapoport , Pedro Falcato , harry@kernel.org, akpm@linux-foundation.org, ljs@kernel.org, vbabka@kernel.org, jannh@google.com, peterx@redhat.com, brauner@kernel.org, viro@zeniv.linux.org.uk, jack@suse.cz, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, usama.arif@linux.dev Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 4DD191C0005 X-Stat-Signature: djnrrddohobqf149q85tk9cjespsqiqq X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1775803903-448759 X-HE-Meta: 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 H5Aoo6JR 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Thanks, Liam. Andrew has already picked up the patch and added the stable t= ag. I'll make sure to include it from the start next time. On Thu, Apr 9, 2026 at 11:16=E2=80=AFPM Liam R. Howlett wrote: > > * Denis M. Karpov [260409 11:54]: > > On Thu, Apr 9, 2026 at 6:17=E2=80=AFPM Mike Rapoport = wrote: > > > On Thu, Apr 09, 2026 at 01:30:07PM +0100, Pedro Falcato wrote: > > > > This looks relatively safe. However, I'm not sure if we want this i= n stable. > > > > This has been broken for 11 years now, with no complaints. > > > > > > I believe Denis has a new usecase that wasn't there for those 11 year= s :) > > > > > > Denis, can you share more details about your usecase for us to better > > > understand importance of backporting this to stable? > > Hello Mike. > > Actually, there is nothing new about the use case. We simply started us= ing > > UFFD instead of the classic mprotect approach in the binary translator = to > > track application writes. During development, we encountered this bug. > > The translator cannot control where the translated application chooses > > to map its > > memory and if the app requires a low-address area, UFFD fails, whereas > > mprotect would work just fine. I believe this is a genuine logic bug ra= ther than > > an improvement, and I would appreciate including the fix in stable. > > Then you should have cc'ed stable (with the tag too). > > I'm fine with it backported or not. > > Reviewed-by: Liam R. Howlett >