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Wed, 09 Sep 2026 13:11:06 -0700 (PDT) Date: Thu, 10 Sep 2026 05:11:03 +0900 Message-ID: From: Hajime Tazaki To: akpm@linux-foundation.org Cc: tasos.papagiannnis@gmail.com, linux-mm@kvack.org, liam@infradead.org, ljs@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/nommu: Reject wrapping ranges in access_remote_vm() In-Reply-To: <20260909001341.6a7c3556259f7cf9a79c1da7@linux-foundation.org> References: <20260909064231.18693-1-tasos.papagiannnis@gmail.com> <20260909001341.6a7c3556259f7cf9a79c1da7@linux-foundation.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/27.2 Mule/6.0 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII Hello, On Wed, 09 Sep 2026 16:13:41 +0900, Andrew Morton wrote: > > On Wed, 9 Sep 2026 09:42:31 +0300 Anastasios Papagiannis wrote: > > > The NOMMU implementation of access_process_vm() rejects address ranges > > whose end wraps around, but access_remote_vm() bypasses this check even > > though both functions delegate to __access_remote_vm(). > > > > Move the wraparound check into __access_remote_vm() so it applies to > > both entry points. > > lgtm, thanks. > > > This is originally reported in [1]. > > > > [1] https://lore.kernel.org/bpf/4ef240a5bea36ff84df9589671367832860795159386a4c8fba546a0fa8b786f@mail.kernel.org/ > > Ah, bpfbot scored one. > > Sashiko might have found more issues in there: > https://sashiko.dev/#/patchset/20260909064231.18693-1-tasos.papagiannnis@gmail.com > > I'll optimistically cc Hajime Tazaki, who has been doing some NOMMU > work recently. I got a similar review (from Sashiko) that current use of !vma->vm_file isn't appropriate and should use vma_set_anonymous(). IIUC that case happens only (I may miss something) with /dev/zero (via mmap_zero_prepare()). I also had a patch but am currently waiting for Lorenzo's input for his work on /dev/zero, which mentioned in his reply. https://lore.kernel.org/linux-mm/an8BlTgk7sc5vFJ1@lucifer/ Thus 3 comments of Sashiko (all about vma->vm_file) can be addressed in future, and are not needed an immediate fix. I wish to ask this to Lorenzo too. -- Hajime