From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 B5C563EE1D6; Thu, 18 Jun 2026 10:31:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781778685; cv=none; b=PZV2f4Eu5iccPX3UPEAJpOfXyXsNhFp31BEsi/7tf3QiKaIZjQVasV4aWGoBbyuqTg9QpvSJo8LT/I1SjlBbByL3a1XXxutwVqnLrMaR0e7q5biNOGPLNQSD1guEfKi9opCAs5j/YyNbKGYX3hF4M49TAbmMlqUJxmmhsFCGxq4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781778685; c=relaxed/simple; bh=ZExVmpqJJOTF2SzP7Wp3BvflZl7cOEZkqGXVKZl1YrA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=uLTw8sVxOILtBDjzS25q8O4kDmvidOO1Cc6ss4DeG61KLhdIbQE5REbjhQYLWTD2faZVs/0WnYgOO/bShsp2FNbxfDWDJvnFEoP93UvW9hP1JcGeZeDcCV0MCWt1+cADKx3iZLgJRfWo6HlAlJ6wG9TjKD2J+QDRjg1DA9XhXGY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=0daqihh3; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="0daqihh3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5887A1F000E9; Thu, 18 Jun 2026 10:31:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1781778679; bh=dYbSQiPv7l/OGFTh2XQKuRySccfha0qxOj/Lg5DWCj4=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=0daqihh3dqrxB5uzri4YRnberXMsJIwTzQUPfWklFWJFmUmMk7X2KgTgJsc6uek8L o3MVAEkr4Ns8wQT8+QsWDXTuJ8oxdbgYdx3hrMqTCY7ryP83dUfq2i+1W1pB9zRo54 QM7fSIsq1h7jFVnoGJWGQ+3nUyacmR5u99SWTbPs= Date: Thu, 18 Jun 2026 12:31:33 +0200 From: Greg Kroah-Hartman To: Yue Sun Cc: Oliver Neukum , Kees Cook , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller@googlegroups.com Subject: Re: [Bug]KASAN: slab-use-after-free Read in iowarrior_release Message-ID: <2026061821-wilder-curable-0619@gregkh> References: <20260618080204.38322-1-samsun1006219@gmail.com> Precedence: bulk X-Mailing-List: linux-usb@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: <20260618080204.38322-1-samsun1006219@gmail.com> On Thu, Jun 18, 2026 at 04:02:04PM +0800, Yue Sun wrote: > Hello, > > I would like to report a use-after-free in the iowarrior USB misc > driver. The crash was found by local syzkaller testing with USB gadget > emulation. Although the crash was collected on an older kernel, I also > confirmed that the same issue is still present on the latest kernel > commit I checked, 6b5a2b7d9bc1 (v7.1-2765-g6b5a2b7d9bc1). > > Observed kernel/configuration > ============================= > > Relevant config: > > CONFIG_USB_IOWARRIOR=y > CONFIG_USB_RAW_GADGET=y > CONFIG_USB_DUMMY_HCD=y > CONFIG_KASAN=y > CONFIG_KASAN_GENERIC=y > CONFIG_PREEMPT=y > > Test environment: > > QEMU 6.2.0, x86_64, 2 CPUs, 4096 MB RAM > > The following is the raw KASAN report excerpt from the syzkaller crash: > > ================================================================== > BUG: KASAN: slab-use-after-free in __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline] > BUG: KASAN: slab-use-after-free in _raw_spin_lock_irqsave+0x3d/0x60 kernel/locking/spinlock.c:166 > Read of size 1 at addr ff110000238d3020 by task syz.0.924/37593 > > CPU: 0 UID: 0 PID: 37593 Comm: syz.0.924 Tainted: G L 7.1.0-rc3-00362-g6916d5703ddf-dirty #35 PREEMPT(full) > Tainted: [L]=SOFTLOCKUP > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 > Call Trace: > > __dump_stack lib/dump_stack.c:94 [inline] > dump_stack_lvl+0x116/0x1b0 lib/dump_stack.c:120 > print_address_description mm/kasan/report.c:378 [inline] > print_report+0xf1/0x5c0 mm/kasan/report.c:482 > kasan_report+0xca/0x100 mm/kasan/report.c:595 > __kasan_check_byte+0x3a/0x50 mm/kasan/common.c:574 > kasan_check_byte include/linux/kasan.h:402 [inline] > lock_acquire kernel/locking/lockdep.c:5842 [inline] > lock_acquire+0x132/0x360 kernel/locking/lockdep.c:5825 > __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline] > _raw_spin_lock_irqsave+0x3d/0x60 kernel/locking/spinlock.c:166 > __mutex_unlock_slowpath+0x182/0x880 kernel/locking/mutex.c:1015 > iowarrior_release+0x231/0x2c0 drivers/usb/misc/iowarrior.c:678 > __fput+0x402/0xb60 fs/file_table.c:510 > task_work_run+0x16b/0x260 kernel/task_work.c:233 > resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] > __exit_to_user_mode_loop kernel/entry/common.c:67 [inline] > exit_to_user_mode_loop+0x121/0x570 kernel/entry/common.c:98 > __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline] > syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:238 [inline] > syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline] > do_syscall_64+0x737/0xf80 arch/x86/entry/syscall_64.c:100 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > RIP: 0033:0x7f9eb63b561d > Code: 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007f9eb8356f68 EFLAGS: 00000246 ORIG_RAX: 0000000000000128 > RAX: ffffffffffffffb9 RBX: 00007f9eb76b0020 RCX: 00007f9eb63b561d > RDX: 0000000000000001 RSI: 0000200000000240 RDI: 0000000000000005 > RBP: 0000000000000056 R08: 0000000000000004 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 > R13: 0000000000000000 R14: 00007f9eb6351640 R15: 00007f9eb8337000 > > > Allocated by task 10489: > kasan_save_stack+0x24/0x50 mm/kasan/common.c:57 > kasan_save_track+0x14/0x30 mm/kasan/common.c:78 > poison_kmalloc_redzone mm/kasan/common.c:398 [inline] > __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415 > kmalloc_noprof include/linux/slab.h:950 [inline] > kzalloc_noprof include/linux/slab.h:1188 [inline] > iowarrior_probe+0x87/0x13a0 drivers/usb/misc/iowarrior.c:766 > usb_probe_interface+0x30e/0xac0 drivers/usb/core/driver.c:396 > call_driver_probe drivers/base/dd.c:631 [inline] > really_probe+0x252/0xb20 drivers/base/dd.c:709 > __driver_probe_device+0x3d3/0x4f0 drivers/base/dd.c:871 > driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:901 > __device_attach_driver+0x1db/0x340 drivers/base/dd.c:1029 > bus_for_each_drv+0x14b/0x1d0 drivers/base/bus.c:500 > __device_attach+0x1ee/0x4f0 drivers/base/dd.c:1101 > device_initial_probe+0xaa/0xc0 drivers/base/dd.c:1156 > bus_probe_device+0x64/0x150 drivers/base/bus.c:613 > device_add+0x1169/0x1930 drivers/base/core.c:3706 > usb_set_configuration+0x1346/0x1e90 drivers/usb/core/message.c:2268 > usb_generic_driver_probe+0xb7/0x110 drivers/usb/core/generic.c:250 > usb_probe_device+0xed/0x400 drivers/usb/core/driver.c:291 > call_driver_probe drivers/base/dd.c:631 [inline] > really_probe+0x252/0xb20 drivers/base/dd.c:709 > __driver_probe_device+0x3d3/0x4f0 drivers/base/dd.c:871 > driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:901 > __device_attach_driver+0x1db/0x340 drivers/base/dd.c:1029 > bus_for_each_drv+0x14b/0x1d0 drivers/base/bus.c:500 > __device_attach+0x1ee/0x4f0 drivers/base/dd.c:1101 > device_initial_probe+0xaa/0xc0 drivers/base/dd.c:1156 > bus_probe_device+0x64/0x150 drivers/base/bus.c:613 > device_add+0x1169/0x1930 drivers/base/core.c:3706 > usb_new_device+0xd2c/0x1ac0 drivers/usb/core/hub.c:2695 > hub_port_connect drivers/usb/core/hub.c:5567 [inline] > hub_port_connect_change drivers/usb/core/hub.c:5707 [inline] > port_event drivers/usb/core/hub.c:5871 [inline] > hub_event+0x2eff/0x5030 drivers/usb/core/hub.c:5953 > process_one_work+0xc57/0x2240 kernel/workqueue.c:3594 > process_scheduled_works kernel/workqueue.c:3703 [inline] > worker_thread+0x693/0xeb0 kernel/workqueue.c:3784 > kthread+0x38d/0x4a0 kernel/kthread.c:436 > ret_from_fork+0xb09/0xdb0 arch/x86/kernel/process.c:158 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 > > Freed by task 48: > kasan_save_stack+0x24/0x50 mm/kasan/common.c:57 > kasan_save_track+0x14/0x30 mm/kasan/common.c:78 > kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:584 > poison_slab_object mm/kasan/common.c:253 [inline] > __kasan_slab_free+0x61/0x80 mm/kasan/common.c:285 > kasan_slab_free include/linux/kasan.h:235 [inline] > slab_free_hook mm/slub.c:2689 [inline] > slab_free mm/slub.c:6250 [inline] > kfree+0x2d6/0x6d0 mm/slub.c:6565 > iowarrior_delete drivers/usb/misc/iowarrior.c:249 [inline] > iowarrior_disconnect+0x210/0x270 drivers/usb/misc/iowarrior.c:921 > usb_unbind_interface+0x1e8/0x9e0 drivers/usb/core/driver.c:458 > device_remove drivers/base/dd.c:621 [inline] > device_remove+0x125/0x170 drivers/base/dd.c:613 > __device_release_driver drivers/base/dd.c:1352 [inline] > device_release_driver_internal+0x45e/0x630 drivers/base/dd.c:1375 > bus_remove_device+0x2ba/0x570 drivers/base/bus.c:657 > device_del+0x396/0x9d0 drivers/base/core.c:3895 > usb_disable_device+0x35c/0x810 drivers/usb/core/message.c:1478 > usb_disconnect+0x2df/0xa00 drivers/usb/core/hub.c:2345 > hub_port_connect drivers/usb/core/hub.c:5407 [inline] > hub_port_connect_change drivers/usb/core/hub.c:5707 [inline] > port_event drivers/usb/core/hub.c:5871 [inline] > hub_event+0x1ece/0x5030 drivers/usb/core/hub.c:5953 > process_one_work+0xc57/0x2240 kernel/workqueue.c:3594 > process_scheduled_works kernel/workqueue.c:3703 [inline] > worker_thread+0x693/0xeb0 kernel/workqueue.c:3784 > kthread+0x38d/0x4a0 kernel/kthread.c:436 > ret_from_fork+0xb09/0xdb0 arch/x86/kernel/process.c:158 > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 > > The buggy address belongs to the object at ff110000238d3000 > which belongs to the cache kmalloc-1k of size 1024 > The buggy address is located 32 bytes inside of > freed 1024-byte region [ff110000238d3000, ff110000238d3400) > > Memory state around the buggy address: > ff110000238d2f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > ff110000238d2f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > >ff110000238d3000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ^ > ff110000238d3080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ff110000238d3100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ================================================================== > > Root cause analysis > =================== > > iowarrior_open() stores a raw struct iowarrior pointer in > file->private_data. The object lifetime is controlled only by the > dev->opened and dev->present state flags. These flags are not sufficient > to protect the object across the file release path and the USB disconnect > path. > > In the observed crash, iowarrior_release() is still returning through > mutex_unlock(&dev->mutex) while iowarrior_disconnect(), running from the > USB hub worker, observes dev->opened == 0 and frees the same object via > iowarrior_delete(). KASAN then reports a use-after-free on dev->mutex > inside __mutex_unlock_slowpath(). > > This matches the mutex_unlock() lifetime rule documented in > kernel/locking/mutex.c: > > The caller must ensure that the mutex stays alive until this function has > returned - mutex_unlock() can NOT directly be used to release an object such > that another concurrent task can free it. > Mutexes are different from spinlocks & refcounts in this aspect. > > The iowarrior release/disconnect paths can violate this rule because > iowarrior_disconnect() can free dev while iowarrior_release() is still > inside mutex_unlock(&dev->mutex). > > One interleaving matching the KASAN report is: > > CPU 0: close()/__fput()/iowarrior_release() > CPU 1: USB hub workqueue/iowarrior_disconnect() > > CPU 0 CPU 1 > ----- ----- > dev = file->private_data > mutex_lock(&dev->mutex) > dev->opened = 0 > if (dev->present) { > usb_kill_urb(dev->int_in_urb) > wake_up_interruptible(&dev->read_wait) > wake_up_interruptible(&dev->write_wait) > mutex_unlock(&dev->mutex) > enters __mutex_unlock_slowpath() > // while still releasing/waking a waiter > mutex_lock(&dev->mutex) > dev->present = 0 > if (!dev->opened) { > mutex_unlock(&dev->mutex) > iowarrior_delete(dev) > kfree(dev) > } > // continues touching dev->mutex > KASAN reports UAF in _raw_spin_lock_irqsave() > from __mutex_unlock_slowpath() > > The freed-by stack confirms that the object is freed from the asynchronous > USB disconnect path running as hub_event on a worker thread. Unfortunately, > I do not have a minimized standalone reproducer yet. > > If you have any questions, please let me know. Great, can you please submit a patch to fix this? thanks, greg k-h