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X-CSE-ConnectionGUID: TIBjqwjaQdixn4QqvPv5aw== X-CSE-MsgGUID: 4tUGMP+NTvmuq8nKFWuvaw== X-IronPort-AV: E=McAfee;i="6800,10657,11531"; a="59860673" X-IronPort-AV: E=Sophos;i="6.17,312,1747724400"; d="scan'208";a="59860673" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by orvoesa109.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Sep 2025 03:43:24 -0700 X-CSE-ConnectionGUID: 9nOXyxQKSdCHClEC2g3abg== X-CSE-MsgGUID: avBgIAJJSQ6PHmEyKVpVow== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,257,1751266800"; d="scan'208";a="173725818" Received: from pgcooper-mobl3.ger.corp.intel.com (HELO kekkonen.fi.intel.com) ([10.245.244.3]) by orviesa008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Sep 2025 03:43:21 -0700 Received: from kekkonen.localdomain (localhost [IPv6:::1]) by kekkonen.fi.intel.com (Postfix) with SMTP id 2DEC61201BB; Thu, 11 Sep 2025 13:43:17 +0300 (EEST) Date: Thu, 11 Sep 2025 13:43:17 +0300 Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs, Bertel Jungin Aukio 5, 02600 Espoo From: Sakari Ailus To: Edward Adam Davis Cc: laurent.pinchart@ideasonboard.com, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, mchehab@kernel.org, syzbot+031d0cfd7c362817963f@syzkaller.appspotmail.com, syzkaller-bugs@googlegroups.com Subject: Re: [PATCH Next V2] media: mc: Clear minor number before put device Message-ID: References: <20250910092233.GA20904@pendragon.ideasonboard.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: Hi Edward, On Wed, Sep 10, 2025 at 06:31:45PM +0800, Edward Adam Davis wrote: > syzbot report a slab-use-after-free in media_devnode_unregister. > > The following calltrace shows the entire process of UAF generation: > > hub_event()-> > port_event()-> > hub_port_connect_change()-> > hub_port_connect()-> > usb_disconnect()-> > usb_disable_device()-> > device_del()-> > bus_remove_device()-> > device_release_driver_internal()-> > __device_release_driver()-> > device_remove()-> > usb_unbind_interface()-> > em28xx_usb_disconnect()-> > em28xx_release_resources()-> > em28xx_unregister_media_device()-> > media_device_unregister()-> > media_devnode_unregister()-> > put_device()-> > media_devnode_release()-> > kfree(devnode) > clear_bit(devnode->minor, media_devnode_nums) > > [1] kfree(devnode), after this code is executed, devnode is released. > [2] clear_bit(devnode->minor, media_devnode_nums), this accesses the > freed devnode, trigger uaf > > We clear the device's minor num before freeing devnode to avoid a UAF. > > Fixes: 9e14868dc952 ("media: mc: Clear minor number reservation at unregistration time") > Reported-by: syzbot+031d0cfd7c362817963f@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=031d0cfd7c362817963f > Tested-by: syzbot+031d0cfd7c362817963f@syzkaller.appspotmail.com > Signed-off-by: Edward Adam Davis Thanks for the update. However, v1 was already merged. I'll mark this as "not applicable". -- Kind regards, Sakari Ailus