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[188.141.5.72]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48dfd4f8bd9sm14785161f8f.35.2026.10.17.19.59.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 17 Oct 2026 19:59:09 -0700 (PDT) From: David Carlier To: Lorenzo Stoakes Cc: Andrew Morton , David Hildenbrand , "Liam R . Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , Jaroslav Kysela , Takashi Iwai , Kazuki Hanai , linux-mm@kvack.org, linux-sound@vger.kernel.org, linux-kernel@vger.kernel.org, David Carlier Subject: Re: [PATCH v6 16/39] mm/vma: only allow mmap to clear VMA_MAYWRITE_BIT if not mm-managed Date: Sun, 18 Oct 2026 03:59:05 +0100 Message-ID: <20261018025905.201296-1-devnexen@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261013-b4-mmap-prepare-vma-flag-sanify-v6-16-1aa3c9b139f9@kernel.org> References: <20261013-b4-mmap-prepare-vma-flag-sanify-v6-16-1aa3c9b139f9@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Lorenzo, I think one site was missed: usb_stream_hwdep_mmap() in sound/usb/usx2y/us122l.c clears VM_MAYWRITE on the read buffer since 71c610aeb177 ("ALSA: us122l: Prevent write upgrades for read mappings"), but sets neither VM_PFNMAP nor VM_MIXEDMAP (pages come from .fault via vmf->page, like the PCM status page in 13/39). So a MAP_PRIVATE mapping of the read buffer, or MAP_SHARED on an O_RDWR fd, now hits the WARN_ON_ONCE in mmap_validate() and fails with -EINVAL. The VM_MAYWRITE clear is a security fix, and the VMA must stay expandable for mremap(), so converting it like 13/39 or setting VM_MIXEDMAP seems the way to go. Found by code reading, not tested on hardware. Cheers