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Using the syzkaller kernel fuzzer, Andrey Konovalov generated the following error in gadgetfs: > BUG: KASAN: use-after-free in __lock_acquire+0x3069/0x3690 > kernel/locking/lockdep.c:3246 > Read of size 8 at addr ffff88003a2bdaf8 by task kworker/3:1/903 > > CPU: 3 PID: 903 Comm: kworker/3:1 Not tainted 4.12.0-rc4+ #35 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > Workqueue: usb_hub_wq hub_event > Call Trace: > __dump_stack lib/dump_stack.c:16 [inline] > dump_stack+0x292/0x395 lib/dump_stack.c:52 > print_address_description+0x78/0x280 mm/kasan/report.c:252 > kasan_report_error mm/kasan/report.c:351 [inline] > kasan_report+0x230/0x340 mm/kasan/report.c:408 > __asan_report_load8_noabort+0x19/0x20 mm/kasan/report.c:429 > __lock_acquire+0x3069/0x3690 kernel/locking/lockdep.c:3246 > lock_acquire+0x22d/0x560 kernel/locking/lockdep.c:3855 > __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] > _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:151 > spin_lock include/linux/spinlock.h:299 [inline] > gadgetfs_suspend+0x89/0x130 drivers/usb/gadget/legacy/inode.c:1682 > set_link_state+0x88e/0xae0 drivers/usb/gadget/udc/dummy_hcd.c:455 > dummy_hub_control+0xd7e/0x1fb0 drivers/usb/gadget/udc/dummy_hcd.c:2074 > rh_call_control drivers/usb/core/hcd.c:689 [inline] > rh_urb_enqueue drivers/usb/core/hcd.c:846 [inline] > usb_hcd_submit_urb+0x92f/0x20b0 drivers/usb/core/hcd.c:1650 > usb_submit_urb+0x8b2/0x12c0 drivers/usb/core/urb.c:542 > usb_start_wait_urb+0x148/0x5b0 drivers/usb/core/message.c:56 > usb_internal_control_msg drivers/usb/core/message.c:100 [inline] > usb_control_msg+0x341/0x4d0 drivers/usb/core/message.c:151 > usb_clear_port_feature+0x74/0xa0 drivers/usb/core/hub.c:412 > hub_port_disable+0x123/0x510 drivers/usb/core/hub.c:4177 > hub_port_init+0x1ed/0x2940 drivers/usb/core/hub.c:4648 > hub_port_connect drivers/usb/core/hub.c:4826 [inline] > hub_port_connect_change drivers/usb/core/hub.c:4999 [inline] > port_event drivers/usb/core/hub.c:5105 [inline] > hub_event+0x1ae1/0x3d40 drivers/usb/core/hub.c:5185 > process_one_work+0xc08/0x1bd0 kernel/workqueue.c:2097 > process_scheduled_works kernel/workqueue.c:2157 [inline] > worker_thread+0xb2b/0x1860 kernel/workqueue.c:2233 > kthread+0x363/0x440 kernel/kthread.c:231 > ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:424 > > Allocated by task 9958: > save_stack_trace+0x1b/0x20 arch/x86/kernel/stacktrace.c:59 > save_stack+0x43/0xd0 mm/kasan/kasan.c:513 > set_track mm/kasan/kasan.c:525 [inline] > kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:617 > kmem_cache_alloc_trace+0x87/0x280 mm/slub.c:2745 > kmalloc include/linux/slab.h:492 [inline] > kzalloc include/linux/slab.h:665 [inline] > dev_new drivers/usb/gadget/legacy/inode.c:170 [inline] > gadgetfs_fill_super+0x24f/0x540 drivers/usb/gadget/legacy/inode.c:1993 > mount_single+0xf6/0x160 fs/super.c:1192 > gadgetfs_mount+0x31/0x40 drivers/usb/gadget/legacy/inode.c:2019 > mount_fs+0x9c/0x2d0 fs/super.c:1223 > vfs_kern_mount.part.25+0xcb/0x490 fs/namespace.c:976 > vfs_kern_mount fs/namespace.c:2509 [inline] > do_new_mount fs/namespace.c:2512 [inline] > do_mount+0x41b/0x2d90 fs/namespace.c:2834 > SYSC_mount fs/namespace.c:3050 [inline] > SyS_mount+0xb0/0x120 fs/namespace.c:3027 > entry_SYSCALL_64_fastpath+0x1f/0xbe > > Freed by task 9960: > save_stack_trace+0x1b/0x20 arch/x86/kernel/stacktrace.c:59 > save_stack+0x43/0xd0 mm/kasan/kasan.c:513 > set_track mm/kasan/kasan.c:525 [inline] > kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:590 > slab_free_hook mm/slub.c:1357 [inline] > slab_free_freelist_hook mm/slub.c:1379 [inline] > slab_free mm/slub.c:2961 [inline] > kfree+0xed/0x2b0 mm/slub.c:3882 > put_dev+0x124/0x160 drivers/usb/gadget/legacy/inode.c:163 > gadgetfs_kill_sb+0x33/0x60 drivers/usb/gadget/legacy/inode.c:2027 > deactivate_locked_super+0x8d/0xd0 fs/super.c:309 > deactivate_super+0x21e/0x310 fs/super.c:340 > cleanup_mnt+0xb7/0x150 fs/namespace.c:1112 > __cleanup_mnt+0x1b/0x20 fs/namespace.c:1119 > task_work_run+0x1a0/0x280 kernel/task_work.c:116 > exit_task_work include/linux/task_work.h:21 [inline] > do_exit+0x18a8/0x2820 kernel/exit.c:878 > do_group_exit+0x14e/0x420 kernel/exit.c:982 > get_signal+0x784/0x1780 kernel/signal.c:2318 > do_signal+0xd7/0x2130 arch/x86/kernel/signal.c:808 > exit_to_usermode_loop+0x1ac/0x240 arch/x86/entry/common.c:157 > prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline] > syscall_return_slowpath+0x3ba/0x410 arch/x86/entry/common.c:263 > entry_SYSCALL_64_fastpath+0xbc/0xbe > > The buggy address belongs to the object at ffff88003a2bdae0 > which belongs to the cache kmalloc-1024 of size 1024 > The buggy address is located 24 bytes inside of > 1024-byte region [ffff88003a2bdae0, ffff88003a2bdee0) > The buggy address belongs to the page: > page:ffffea0000e8ae00 count:1 mapcount:0 mapping: (null) > index:0x0 compound_mapcount: 0 > flags: 0x100000000008100(slab|head) > raw: 0100000000008100 0000000000000000 0000000000000000 0000000100170017 > raw: ffffea0000ed3020 ffffea0000f5f820 ffff88003e80efc0 0000000000000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: > ffff88003a2bd980: fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > ffff88003a2bda00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > >ffff88003a2bda80: fc fc fc fc fc fc fc fc fc fc fc fc fb fb fb fb > ^ > ffff88003a2bdb00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ffff88003a2bdb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ================================================================== What this means is that the gadgetfs_suspend() routine was trying to access dev->lock after it had been deallocated. The root cause is a race in the dummy_hcd driver; the dummy_udc_stop() routine can race with the rest of the driver because it contains no locking. And even when proper locking is added, it can still race with the set_link_state() function because that function incorrectly drops the private spinlock before invoking any gadget driver callbacks. The result of this race, as seen above, is that set_link_state() can invoke a callback in gadgetfs even after gadgetfs has been unbound from dummy_hcd's UDC and its private data structures have been deallocated. include/linux/usb/gadget.h documents that the ->reset, ->disconnect, ->suspend, and ->resume callbacks may be invoked in interrupt context. In general this is necessary, to prevent races with gadget driver removal. This patch fixes dummy_hcd to retain the spinlock across these calls, and it adds a spinlock acquisition to dummy_udc_stop() to prevent the race. The net2280 driver makes the same mistake of dropping the private spinlock for its ->disconnect and ->reset callback invocations. The patch fixes it too. Lastly, since gadgetfs_suspend() may be invoked in interrupt context, it cannot assume that interrupts are enabled when it runs. It must use spin_lock_irqsave() instead of spin_lock_irq(). The patch fixes that bug as well. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Reported-and-tested-by: Andrey Konovalov <andreyknvl@google.com> CC: <stable@vger.kernel.org> Acked-by: Felipe Balbi <felipe.balbi@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.