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AHgh+Ro5wITSS4UL89M/59Fw0m9Fuurdcpn2Ot3yGZCLSuRUGiZpQNjDziMcdAS9iZCczUVU7NVB/mD13KfjG+Q=@vger.kernel.org X-Gm-Message-State: AOJu0YwsMidcChToqDYz6uEwAvay6Lc9I5BYV4r00EgxJ2W0hd8gTx6l M5Goh4ZEh/VaKrgwPxDyHWUh6KYPh8H3580wFpvgtSnVU68Y0+KSoIJUQFd7ZrMSZVqnO4BUdrd 9fxJXgPj9fzGvFlS2aOfHj1jKC0IUM1Y= X-Gm-Gg: AfdE7clv0Ph+y0PsR5b+GhNIwjnnDbzrLMAZClLo1SY57ZesGOnQ5UunqJOvO/VubFD bzfvMdKsl9cXS3TCJ2wpaTfJLr8VNWZGGHwheQ848yhbauLJWbNCf6SQ3tSvqvar9h43TjDYvQc Idv1O1YKjNYTKM7DeiZnEJvDExcheT0V9Dj53pza6Tn80PT8cEp89koKsbNZRNb6Og0J3/GWoIe MwmUcsdk+fXXDH2LUnc0alUED1gTBnZBDVKAE1elP40w7R5RFe4WK7u5X07XiH1jfeTf2P7Xa/I /3s5ivu6G0PaukZM7RiOVcu192k= X-Received: by 2002:a17:90b:2b43:b0:38d:ecfe:41ac with SMTP id 98e67ed59e1d1-38e29eb265fmr2851845a91.0.1784131688289; Wed, 15 Jul 2026 09:08:08 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20260715142337.22811-1-harimishal1@gmail.com> <20260715142337.22811-3-harimishal1@gmail.com> <20260715115018-mutt-send-email-mst@kernel.org> In-Reply-To: <20260715115018-mutt-send-email-mst@kernel.org> From: Hari Mishal Date: Wed, 15 Jul 2026 18:07:56 +0200 X-Gm-Features: AUfX_mxeev5EctzqqOhnXkkLp1lW-oPLOPqW61BCZQn7an58NL9TZTOsb6yp6yk Message-ID: Subject: Re: [PATCH 2/4] virtio_input: validate device-reported multitouch slot count To: "Michael S. Tsirkin" Cc: Amit Shah , Arnd Bergmann , Greg Kroah-Hartman , Gerd Hoffmann , Jason Wang , David Hildenbrand , Henrik Rydberg , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, linux-input@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, Jul 15, 2026 at 5:50=E2=80=AFPM Michael S. Tsirkin = wrote: > > On Wed, Jul 15, 2026 at 04:22:41PM +0200, Hari Mishal wrote: > > nslots is derived from the ABS_MT_SLOT maximum reported by the > > virtio device. A device could report a bogus maximum (e.g. -1) > > making nslots =3D 0, which input_mt_init_slots() does not reject; > > it returns success without allocating any slot storage, silently > > leaving the device registered as multitouch capable with no > > backing state. > > So let's disable multitouch instead? > So rather than failing the whole probe, just warn and clear ABS_MT_SLOT from absbit in that case, so the rest of the device still registers? I took my lead from input_mt_init_slots(), which has its own internal cap and returns -EINVAL when the device reports more than 1024 slots. Shall I modify that case to get the same "warn and disable multitouch" for consistency, or is a hard failure better there since it's a different type of bad device data? Happy to fix it either way! Just want to confirm before sending V2. Cheers, Hari