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[34.125.95.99]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a09773e7c3sm689822a91.17.2026.09.23.13.39.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Sep 2026 13:39:39 -0700 (PDT) Date: Wed, 23 Sep 2026 20:39:35 +0000 From: Carlos Llamas To: Hui Peng Cc: gregkh@linuxfoundation.org, arve@android.com, tkjos@android.com, brauner@kernel.org, aliceryhl@google.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] binder: forbid VMA splitting and mremap on binder mmap Message-ID: References: <20260919213653.3317260-1-benquike@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260919213653.3317260-1-benquike@gmail.com> On Sat, Sep 19, 2026 at 09:36:53PM +0000, Hui Peng wrote: > `binder_vm_ops` does not implement `.may_split` or `.mremap`, and > `binder_vma_close()` unconditionally calls > `binder_alloc_vma_close(&proc->alloc)` (which sets `alloc->vma = NULL`). > > If userspace calls `munmap()` on a sub-range of the binder mapping (or > `mremap()` to move/split a sub-range), the VMA is split into two VMAs > sharing the same `binder_proc`, and `binder_vma_close()` runs on the > unmapped half and clears `alloc->vma = NULL` while the remaining VMA > stays mapped in the process's address space, desynchronizing > `alloc->vma` from the remaining VMA. > > Implement `.may_split` and `.mremap` returning `-EINVAL` in > `binder_vm_ops` and check `vma->vm_start == proc->alloc.vm_start` in > `binder_vma_close()`. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") This is not correct. Also, this exact fix has been previously sent here: https://lore.kernel.org/all/20260901205250.1638304-1-cmllamas@google.com/ -- Carlos Llamas