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[2a02:8388:e103:2700:4142:6cbb:5953:ad6a]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-62fa5d03befsm70715a12.2.2025.09.17.11.28.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 Sep 2025 11:28:55 -0700 (PDT) Message-ID: Date: Wed, 17 Sep 2025 20:28:54 +0200 Precedence: bulk X-Mailing-List: linux-leds@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: use-after-free in firmware_fallback_sysfs To: Russ Weight Cc: "Lalaev, Andrei" , "rafael@kernel.org" , "gregkh@linuxfoundation.org" , "dakr@kernel.org" , "mcgrof@kernel.org" , "linux-kernel@vger.kernel.org" , "linux-leds@vger.kernel.org" References: <58758ff1-e7d7-4c47-a513-f65bdf777a6a@gmail.com> Content-Language: en-GB From: Andrei Lalaev In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 16.09.2025 22:44, Russ Weight wrote: > On Fri, Sep 12, 2025 at 12:13:30PM +0200, Andrei Lalaev wrote: >> On 12.09.2025 00:35, Russ Weight wrote: >>> >>> On Thu, Sep 04, 2025 at 04:58:45AM +0000, Lalaev, Andrei wrote: >>>> Hi, >>>> >>>> We performed a long-term stability test on the LP5562 driver by repeatedly >>>> downloading different LED firmwares using sysfs interface. >>>> And after some time, we see the following "use-after-free" trace on kernel 6.12.11: >>>> >>>> [ 274.759115] BUG: KASAN: slab-use-after-free in firmware_fallback_sysfs (include/linux/list.h:153 include/linux/list.h:169 drivers/base/firmware_loader/fallback.c:98 drivers/base/firmware_loader/fallback.c:162 drivers/base/firmware_loader/fallback.c:238) >>>> [ 274.766743] Write of size 4 at addr b31d0850 by task kworker/2:2/137 >>>> [ 274.774680] CPU: 2 UID: 0 PID: 137 Comm: kworker/2:2 Tainted: G C 6.12.11 #1 >>>> [ 274.783208] Tainted: [C]=CRAP >>>> [ 274.786215] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree) >>>> [ 274.792775] Workqueue: events request_firmware_work_func >>>> [ 274.798151] Call trace: >>>> [ 274.800720] dump_backtrace from show_stack (arch/arm/kernel/traps.c:259) >>>> [ 274.805827] r7:600f0093 r6:600f0093 r5:b19659b4 r4:00000000 >>>> [ 274.811510] show_stack from dump_stack_lvl (lib/dump_stack.c:122) >>>> [ 274.816613] dump_stack_lvl from print_report (mm/kasan/report.c:378 mm/kasan/report.c:488) >>>> [ 274.822073] r7:000031d0 r6:df7dba00 r5:f13bbb20 r4:b31d0850 >>>> [ 274.827755] print_report from kasan_report (mm/kasan/report.c:603) >>>> [ 274.832885] r10:b2d56c20 r9:cdc89808 r8:00003a98 r7:b0f653ac r6:00000004 r5:00000001 >>>> [ 274.840744] r4:b31d0850 >>>> [ 274.843298] kasan_report from __asan_report_store4_noabort (mm/kasan/report_generic.c:385) >>>> [ 274.849804] r7:b9f72c00 r6:cdc89800 r5:b5d31e00 r4:b5d31e10 >>>> [ 274.855488] __asan_report_store4_noabort from firmware_fallback_sysfs (include/linux/list.h:153 include/linux/list.h:169 drivers/base/firmware_loader/fallback.c:98 drivers/base/firmware_loader/fallback.c:162 drivers/base/firmware_loader/fallback.c:238) >>>> [ 274.863105] firmware_fallback_sysfs from _request_firmware (drivers/base/firmware_loader/main.c:941) >>>> [ 274.869862] r10:f13bbda0 r9:b9f72c80 r8:b19c73d8 r7:00000004 r6:00000000 r5:b5d31e00 >>>> [ 274.877718] r4:f13bbd00 >>>> [ 274.880273] _request_firmware from request_firmware_work_func (drivers/base/firmware_loader/main.c:1196) >>>> [ 274.887226] r10:b9f72e98 r9:b9f72e94 r8:f13bbde0 r7:173ee5d3 r6:00000000 r5:ad2777b0 >>>> [ 274.895097] r4:b9f72e80 >>>> [ 274.897661] request_firmware_work_func from process_one_work (kernel/workqueue.c:3235) >>>> [ 274.904613] r10:00000000 r9:b7d7e1e0 r8:b7d7dd80 r7:d76b53c0 r6:b2013c00 r5:b9f72e80 >>>> [ 274.912469] r4:b2371a00 >>>> [ 274.915024] process_one_work from worker_thread (kernel/workqueue.c:3304 (discriminator 2) kernel/workqueue.c:3391 (discriminator 2)) >>>> [ 274.920823] r10:b2371a2c r9:b2371a00 r8:b9f72e84 r7:b2371a2c r6:d76b53dc r5:a546e345 >>>> [ 274.928678] r4:00000007 >>>> [ 274.931234] worker_thread from kthread (kernel/kthread.c:389) >>>> [ 274.936179] r10:f0933ca0 r9:b2371a00 r8:b7f6b800 r7:b019ad18 r6:b2354880 r5:b7d7dd80 >>>> [ 274.944035] r4:b2354d00 >>>> [ 274.946592] kthread from ret_from_fork (arch/arm/kernel/entry-common.S:138) >>>> [ 274.951350] Exception stack(0xf13bbfb0 to 0xf13bbff8) >>>> [ 274.956435] bfa0: 00000000 00000000 00000000 00000000 >>>> [ 274.964647] bfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 >>>> [ 274.972858] bfe0: 00000000 00000000 00000000 00000000 00000013 00000000 >>>> [ 274.979508] r10:00000000 r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:b01ba280 >>>> [ 274.987365] r4:b2354d00 r3:00000000 >>>> >>>> [ 274.992472] Allocated by task 8 on cpu 0 at 273.209883s: >>>> [ 274.997814] kasan_save_track (mm/kasan/common.c:48 mm/kasan/common.c:68) >>>> [ 274.997858] kasan_save_alloc_info (mm/kasan/generic.c:566) >>>> [ 274.997892] __kasan_kmalloc (mm/kasan/common.c:398) >>>> [ 274.997926] __kmalloc_cache_noprof (mm/slub.c:4319) >>>> [ 274.997957] alloc_lookup_fw_priv (drivers/base/firmware_loader/main.c:131 drivers/base/firmware_loader/main.c:190) >>>> [ 274.997993] _request_firmware (drivers/base/firmware_loader/main.c:769 drivers/base/firmware_loader/main.c:899) >>>> [ 274.998023] request_firmware_work_func (drivers/base/firmware_loader/main.c:1196) >>>> [ 274.998055] process_one_work (kernel/workqueue.c:3235) >>>> [ 274.998084] worker_thread (kernel/workqueue.c:3304 (discriminator 2) kernel/workqueue.c:3391 (discriminator 2)) >>>> [ 274.998112] kthread (kernel/kthread.c:389) >>>> [ 274.998149] ret_from_fork (arch/arm/kernel/entry-common.S:138) >>>> >>>> [ 274.999686] Freed by task 8 on cpu 0 at 273.230581s: >>>> [ 275.004679] kasan_save_track (mm/kasan/common.c:48 mm/kasan/common.c:68) >>>> [ 275.004718] kasan_save_free_info (mm/kasan/generic.c:582 (discriminator 1)) >>>> [ 275.004747] __kasan_slab_free (mm/kasan/common.c:271) >>>> [ 275.004782] kfree (mm/slub.c:4601 (discriminator 3) mm/slub.c:4749 (discriminator 3)) >>>> [ 275.004810] free_fw_priv (drivers/base/firmware_loader/main.c:231) >>>> [ 275.004840] release_firmware (drivers/base/firmware_loader/main.c:604 drivers/base/firmware_loader/main.c:1170 drivers/base/firmware_loader/main.c:1166) >>>> [ 275.004871] lp55xx_firmware_loaded (drivers/leds/leds-lp55xx-common.c:549) leds_lp55xx_common >>>> [ 275.005074] request_firmware_work_func (drivers/base/firmware_loader/main.c:1197) >>>> [ 275.005112] process_one_work (kernel/workqueue.c:3235) >>>> [ 275.005145] worker_thread (kernel/workqueue.c:3304 (discriminator 2) kernel/workqueue.c:3391 (discriminator 2)) >>>> [ 275.005174] kthread (kernel/kthread.c:389) >>>> [ 275.005212] ret_from_fork (arch/arm/kernel/entry-common.S:138) >>>> [ 275.006754] The buggy address belongs to the object at b31d0800 which belongs to the cache kmalloc-128 of size 128 >>>> [ 275.018610] The buggy address is located 80 bytes inside of freed 128-byte region [b31d0800, b31d0880) >>>> [ 275.030938] The buggy address belongs to the physical page: >>>> [ 275.036533] page: refcount:1 mapcount:0 mapping:00000000 index:0x0 pfn:0x131d0 >>>> [ 275.036568] flags: 0x0(zone=0) >>>> [ 275.036598] page_type: f5(slab) >>>> [ 275.036634] raw: 00000000 b2001400 df9544e0 00000002 00000000 00100010 f5000000 00000001 >>>> [ 275.036659] page dumped because: kasan: bad access detected >>>> >>>> [ 275.038189] Memory state around the buggy address: >>>> [ 275.043008] b31d0700: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>>> [ 275.049563] b31d0780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >>>> [ 275.056120] >b31d0800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >>>> [ 275.062669] ^ >>>> [ 275.067831] b31d0880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >>>> [ 275.074386] b31d0900: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc >>>> [ 275.080938] ================================================================== >>>> >>>> I couldn't find any related patches to fix this issue in upstream, so >>>> I have made the following patch to address this issue, but I have some concerns about it. >>>> >>>> Could someone please provide feedback or insights on this? >>>> >>>> ---- >>>> drivers/base/firmware_loader/main.c | 1 + >>>> 1 file changed, 1 insertion(+) >>>> >>>> diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c >>>> index c6664a787..1a49022f4 100644 >>>> --- a/drivers/base/firmware_loader/main.c >>>> +++ b/drivers/base/firmware_loader/main.c >>>> @@ -211,6 +211,7 @@ static void __free_fw_priv(struct kref *ref) >>>> (unsigned int)fw_priv->size); >>>> >>>> list_del(&fw_priv->list); >>>> + list_del(&fw_priv->pending_list); >>> >>> References to &fw_priv->pending_list in this context would need to >>> be bounded with "#ifdef CONFIG_FW_LOADER_USER_HELPER". >>> >>> Have you repeated your long-term stability test with this change? >>> >> >> Hi Russ, >> >> Yes, sure. I had the test running for 2 days, and no "use-after-free" appeared. >> > > Hi Andrei, > > Have you looked at the firmware fallback selftests? These are at > tools/testing/selftests/firmware/fw_fallback.sh. I'm wondering if > these tests could be modified to expose the bug that you found. Can > you take a look? Hm, I didn't know about them. Will take a look then. Thanks for the hint! -- Best regards, Andrei Lalaev