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([2a05:6e02:1041:c10:c456:8337:99aa:2667]) by smtp.googlemail.com with ESMTPSA id d16-20020adfe890000000b0022e035a4e93sm11624681wrm.87.2022.10.04.04.49.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 Oct 2022 04:49:38 -0700 (PDT) Message-ID: Date: Tue, 4 Oct 2022 13:49:36 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [RFC/RFT PATCH resend] thermal: Protect thermal device operations against thermal device removal Content-Language: en-US To: Guenter Roeck , linux-pm@vger.kernel.org Cc: "Rafael J . Wysocki" , Amit Kucheria , Zhang Rui , Lukasz Luba , linux-kernel@vger.kernel.org References: <20221004033936.1047691-1-linux@roeck-us.net> From: Daniel Lezcano In-Reply-To: <20221004033936.1047691-1-linux@roeck-us.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/10/2022 05:39, Guenter Roeck wrote: > A call to thermal_zone_device_unregister() results in thermal device > removal. While the thermal device itself is reference counted and > protected against removal of its associated data structures, the > thermal device operations are owned by the calling code and unprotected. > This may result in crashes such as > > BUG: unable to handle page fault for address: ffffffffc04ef420 > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > PGD 5d60e067 P4D 5d60e067 PUD 5d610067 PMD 110197067 PTE 0 > Oops: 0000 [#1] PREEMPT SMP NOPTI > CPU: 1 PID: 3209 Comm: cat Tainted: G W 5.10.136-19389-g615abc6eb807 #1 02df41ac0b12f3a64f4b34245188d8875bb3bce1 > Hardware name: Google Coral/Coral, BIOS Google_Coral.10068.92.0 11/27/2018 > RIP: 0010:thermal_zone_get_temp+0x26/0x73 > Code: 89 c3 eb d3 0f 1f 44 00 00 55 48 89 e5 41 57 41 56 53 48 85 ff 74 50 48 89 fb 48 81 ff 00 f0 ff ff 77 44 48 8b 83 98 03 00 00 <48> 83 78 10 00 74 36 49 89 f6 4c 8d bb d8 03 00 00 4c 89 ff e8 9f > RSP: 0018:ffffb3758138fd38 EFLAGS: 00010287 > RAX: ffffffffc04ef410 RBX: ffff98f14d7fb000 RCX: 0000000000000000 > RDX: ffff98f17cf90000 RSI: ffffb3758138fd64 RDI: ffff98f14d7fb000 > RBP: ffffb3758138fd50 R08: 0000000000001000 R09: ffff98f17cf90000 > R10: 0000000000000000 R11: ffffffff8dacad28 R12: 0000000000001000 > R13: ffff98f1793a7d80 R14: ffff98f143231708 R15: ffff98f14d7fb018 > FS: 00007ec166097800(0000) GS:ffff98f1bbd00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: ffffffffc04ef420 CR3: 000000010ee9a000 CR4: 00000000003506e0 > Call Trace: > temp_show+0x31/0x68 > dev_attr_show+0x1d/0x4f > sysfs_kf_seq_show+0x92/0x107 > seq_read_iter+0xf5/0x3f2 > vfs_read+0x205/0x379 > __x64_sys_read+0x7c/0xe2 > do_syscall_64+0x43/0x55 > entry_SYSCALL_64_after_hwframe+0x61/0xc6 > > if a thermal device is removed while accesses to its device attributes > are ongoing. > > Use the thermal device mutex to protect device operations. Clear the > device operations pointer in thermal_zone_device_unregister() under > protection of this mutex, and only access it while the mutex is held. > Flatten and simplify device mutex operations to only acquire the mutex > once and hold it instead of acquiring and releasing it several times > during thermal operations. Only validate parameters once at module entry > points after acquiring the mutex. Execute governor operations under mutex > instead of expecting governors to acquire and release it. Does the following series: https://lore.kernel.org/lkml/20220805153834.2510142-1-daniel.lezcano@linaro.org/ goes to the same direction than your proposal? -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog