From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EC61A7D3F4; Wed, 6 Nov 2024 08:40:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730882429; cv=none; b=iBnygQBx2vFMIx9XMubtXYkh6fcFeR7HGEm84vMnNI71EoHQhgGitj97kBKyO9sQvCnSq8C73RjJTqNi6jDFajdiflq5VgGqCbNdyl2/xectRW4AqTod44IzRN0EdCZ4knzlW5cjd2e0t7CdWQmDKc7Y8jaYr1eHHs12H8jRc3E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730882429; c=relaxed/simple; bh=U4H1UkFB2GiREgkJc442onlPdKsWNCgG54uKnyfm/yE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=OaYm89X1SSxQS6Dyj+mYsKirPNwV/asA4Rt7rJbC4hRa5qso29P2Ntc0ycnOfz9DPRpsphO7VXdH+rhQ9IcsqlM9qv1KzYUjrh8XUMIqnaJNEvjyfQbuZGdF3oStN0dLHhKVb16dtJbDwGdC1Ga6WyCdOasrh7ThqqXVetpG60o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bZJ3edXo; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bZJ3edXo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 37D5CC4CECD; Wed, 6 Nov 2024 08:40:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730882428; bh=U4H1UkFB2GiREgkJc442onlPdKsWNCgG54uKnyfm/yE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=bZJ3edXoEfh9dGZK0jiFJthUAZChOZZGR/pTo3ShyIsPj0U8aTOe1AvVvxLR6Tjqs 5tZhSQ8U85XSYeV2/DG3iYo460PUDQpw86RWcON4q1VY+JtCAp8r0zCVGfNFHZdP28 nc9CrJRXKRnDQGX+WnpflWFZ22EkJLEybEwkb147mYEU9Aa4d8n175W8uwiuAHYgYP 4AN70SZMKdITpwp1qA/T+X1joSJug6eRsq60bzBCkH1poDnVD5p4CIT2lkDvQUAAxQ 6xEJIrj2XsYzoO0ELm0K/dHecBEPp8n4YPdG/BlUCZs1jUmzonvtXf9NCdAuRPiIJ8 fUNivVesNfpHw== Date: Wed, 6 Nov 2024 08:40:24 +0000 From: Lee Jones To: anish kumar Cc: Mukesh Ojha , Pavel Machek , linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] leds: class: Protect brightness_show() with led_cdev->led_access mutex Message-ID: <20241106084024.GH1807686@google.com> References: <20241103160527.82487-1-quic_mojha@quicinc.com> Precedence: bulk X-Mailing-List: linux-leds@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Sun, 03 Nov 2024, anish kumar wrote: > On Sun, Nov 3, 2024 at 8:15 AM Mukesh Ojha wrote: > > > > There is NULL pointer issue observed if from Process A where hid device > > being added which results in adding a led_cdev addition and later a > > another call to access of led_cdev attribute from Process B can result > > in NULL pointer issue. > > > > Use mutex led_cdev->led_access to protect access to led->cdev and its > > attribute inside brightness_show() and max_brightness_show() and also > > update the comment for mutex that it should be used to protect the led > > class device fields. > > > > Process A Process B > > > > kthread+0x114 > > worker_thread+0x244 > > process_scheduled_works+0x248 > > uhid_device_add_worker+0x24 > > hid_add_device+0x120 > > device_add+0x268 > > bus_probe_device+0x94 > > device_initial_probe+0x14 > > __device_attach+0xfc > > bus_for_each_drv+0x10c > > __device_attach_driver+0x14c > > driver_probe_device+0x3c > > __driver_probe_device+0xa0 > > really_probe+0x190 > > hid_device_probe+0x130 > > ps_probe+0x990 > > ps_led_register+0x94 > > devm_led_classdev_register_ext+0x58 > > led_classdev_register_ext+0x1f8 > > device_create_with_groups+0x48 > > device_create_groups_vargs+0xc8 > > device_add+0x244 > > kobject_uevent+0x14 > > kobject_uevent_env[jt]+0x224 > > mutex_unlock[jt]+0xc4 > > __mutex_unlock_slowpath+0xd4 > > wake_up_q+0x70 > > try_to_wake_up[jt]+0x48c > > preempt_schedule_common+0x28 > > __schedule+0x628 > > __switch_to+0x174 > > el0t_64_sync+0x1a8/0x1ac > > el0t_64_sync_handler+0x68/0xbc > > el0_svc+0x38/0x68 > > do_el0_svc+0x1c/0x28 > > el0_svc_common+0x80/0xe0 > > invoke_syscall+0x58/0x114 > > __arm64_sys_read+0x1c/0x2c > > ksys_read+0x78/0xe8 > > vfs_read+0x1e0/0x2c8 > > kernfs_fop_read_iter+0x68/0x1b4 > > seq_read_iter+0x158/0x4ec > > kernfs_seq_show+0x44/0x54 > > sysfs_kf_seq_show+0xb4/0x130 > > dev_attr_show+0x38/0x74 > > brightness_show+0x20/0x4c > > dualshock4_led_get_brightness+0xc/0x74 > > > > [ 3313.874295][ T4013] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000060 > > [ 3313.874301][ T4013] Mem abort info: > > [ 3313.874303][ T4013] ESR = 0x0000000096000006 > > [ 3313.874305][ T4013] EC = 0x25: DABT (current EL), IL = 32 bits > > [ 3313.874307][ T4013] SET = 0, FnV = 0 > > [ 3313.874309][ T4013] EA = 0, S1PTW = 0 > > [ 3313.874311][ T4013] FSC = 0x06: level 2 translation fault > > [ 3313.874313][ T4013] Data abort info: > > [ 3313.874314][ T4013] ISV = 0, ISS = 0x00000006, ISS2 = 0x00000000 > > [ 3313.874316][ T4013] CM = 0, WnR = 0, TnD = 0, TagAccess = 0 > > [ 3313.874318][ T4013] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 > > [ 3313.874320][ T4013] user pgtable: 4k pages, 39-bit VAs, pgdp=00000008f2b0a000 > > .. > > > > [ 3313.874332][ T4013] Dumping ftrace buffer: > > [ 3313.874334][ T4013] (ftrace buffer empty) > > .. > > .. > > [ dd3313.874639][ T4013] CPU: 6 PID: 4013 Comm: InputReader > > [ 3313.874648][ T4013] pc : dualshock4_led_get_brightness+0xc/0x74 > > [ 3313.874653][ T4013] lr : led_update_brightness+0x38/0x60 > > [ 3313.874656][ T4013] sp : ffffffc0b910bbd0 > > .. > > .. > > [ 3313.874685][ T4013] Call trace: > > [ 3313.874687][ T4013] dualshock4_led_get_brightness+0xc/0x74 > > [ 3313.874690][ T4013] brightness_show+0x20/0x4c > > [ 3313.874692][ T4013] dev_attr_show+0x38/0x74 > > [ 3313.874696][ T4013] sysfs_kf_seq_show+0xb4/0x130 > > [ 3313.874700][ T4013] kernfs_seq_show+0x44/0x54 > > [ 3313.874703][ T4013] seq_read_iter+0x158/0x4ec > > [ 3313.874705][ T4013] kernfs_fop_read_iter+0x68/0x1b4 > > [ 3313.874708][ T4013] vfs_read+0x1e0/0x2c8 > > [ 3313.874711][ T4013] ksys_read+0x78/0xe8 > > [ 3313.874714][ T4013] __arm64_sys_read+0x1c/0x2c > > [ 3313.874718][ T4013] invoke_syscall+0x58/0x114 > > [ 3313.874721][ T4013] el0_svc_common+0x80/0xe0 > > [ 3313.874724][ T4013] do_el0_svc+0x1c/0x28 > > [ 3313.874727][ T4013] el0_svc+0x38/0x68 > > [ 3313.874730][ T4013] el0t_64_sync_handler+0x68/0xbc > > [ 3313.874732][ T4013] el0t_64_sync+0x1a8/0x1ac > > > > Signed-off-by: Mukesh Ojha > > > reviewed-by: Anish Kumar Please correct this and save it as a key-binding to prevent further typos. -- Lee Jones [李琼斯]