Re: KASAN: use-after-free Read in chaoskey_disconnect

[Andrey Konovalov]

On Wed, Oct 30, 2019 at 1:52 PM syzbot
<syzbot+6d8505fcdf25f00ac276@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    ff6409a6 usb-fuzzer: main usb gadget fuzzer driver
> git tree:       https://github.com/google/kasan.git usb-fuzzer
> console output: https://syzkaller.appspot.com/x/log.txt?x=15e1ba24e00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=3230c37d442895b7
> dashboard link: https://syzkaller.appspot.com/bug?extid=6d8505fcdf25f00ac276
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=169b8904e00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=166f3104e00000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+6d8505fcdf25f00ac276@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> usb 3-1: string descriptor 0 read error: -71
> usb 3-1: USB disconnect, device number 2
> ==================================================================
> BUG: KASAN: use-after-free in atomic_read
> include/asm-generic/atomic-instrumented.h:26 [inline]
> BUG: KASAN: use-after-free in refcount_inc_not_zero_checked+0x72/0x1e0
> lib/refcount.c:123
> Read of size 4 at addr ffff8881cf679820 by task kworker/1:1/1730
>
> CPU: 1 PID: 1730 Comm: kworker/1:1 Not tainted 5.4.0-rc5+ #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Workqueue: usb_hub_wq hub_event
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0xca/0x13e lib/dump_stack.c:113
>   print_address_description.constprop.0+0x36/0x50 mm/kasan/report.c:374
>   __kasan_report.cold+0x1a/0x33 mm/kasan/report.c:506
>   kasan_report+0xe/0x20 mm/kasan/common.c:634
>   check_memory_region_inline mm/kasan/generic.c:185 [inline]
>   check_memory_region+0x128/0x190 mm/kasan/generic.c:192
>   atomic_read include/asm-generic/atomic-instrumented.h:26 [inline]
>   refcount_inc_not_zero_checked+0x72/0x1e0 lib/refcount.c:123
>   refcount_inc_checked+0x12/0x60 lib/refcount.c:156
>   get_task_struct include/linux/sched/task.h:110 [inline]
>   kthread_stop+0x6c/0x610 kernel/kthread.c:554
>   hwrng_unregister+0x190/0x210 drivers/char/hw_random/core.c:538
>   chaoskey_disconnect+0x1b2/0x200 drivers/usb/misc/chaoskey.c:232
>   usb_unbind_interface+0x1bd/0x8a0 drivers/usb/core/driver.c:423
>   __device_release_driver drivers/base/dd.c:1134 [inline]
>   device_release_driver_internal+0x42f/0x500 drivers/base/dd.c:1165
>   bus_remove_device+0x2dc/0x4a0 drivers/base/bus.c:532
>   device_del+0x420/0xb20 drivers/base/core.c:2376
>   usb_disable_device+0x211/0x690 drivers/usb/core/message.c:1237
>   usb_disconnect+0x284/0x8d0 drivers/usb/core/hub.c:2200
>   hub_port_connect drivers/usb/core/hub.c:5035 [inline]
>   hub_port_connect_change drivers/usb/core/hub.c:5324 [inline]
>   port_event drivers/usb/core/hub.c:5470 [inline]
>   hub_event+0x16f2/0x3800 drivers/usb/core/hub.c:5552
>   process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
>   process_scheduled_works kernel/workqueue.c:2331 [inline]
>   worker_thread+0x7ab/0xe20 kernel/workqueue.c:2417
>   kthread+0x318/0x420 kernel/kthread.c:255
>   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
>
> Allocated by task 2:
>   save_stack+0x1b/0x80 mm/kasan/common.c:69
>   set_track mm/kasan/common.c:77 [inline]
>   __kasan_kmalloc mm/kasan/common.c:510 [inline]
>   __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:483
>   slab_post_alloc_hook mm/slab.h:584 [inline]
>   slab_alloc_node mm/slub.c:2779 [inline]
>   kmem_cache_alloc_node+0xdc/0x310 mm/slub.c:2815
>   alloc_task_struct_node kernel/fork.c:169 [inline]
>   dup_task_struct kernel/fork.c:865 [inline]
>   copy_process+0x4201/0x6470 kernel/fork.c:1851
>   _do_fork+0x129/0xec0 kernel/fork.c:2366
>   kernel_thread+0xaa/0xe0 kernel/fork.c:2453
>   create_kthread kernel/kthread.c:278 [inline]
>   kthreadd+0x4a2/0x680 kernel/kthread.c:596
>   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
>
> Freed by task 16:
>   save_stack+0x1b/0x80 mm/kasan/common.c:69
>   set_track mm/kasan/common.c:77 [inline]
>   kasan_set_free_info mm/kasan/common.c:332 [inline]
>   __kasan_slab_free+0x130/0x180 mm/kasan/common.c:471
>   slab_free_hook mm/slub.c:1424 [inline]
>   slab_free_freelist_hook mm/slub.c:1475 [inline]
>   slab_free mm/slub.c:3025 [inline]
>   kmem_cache_free+0xb9/0x380 mm/slub.c:3041
>   __put_task_struct+0x1e2/0x4c0 kernel/fork.c:748
>   put_task_struct include/linux/sched/task.h:119 [inline]
>   delayed_put_task_struct+0x1b4/0x2c0 kernel/exit.c:182
>   __rcu_reclaim kernel/rcu/rcu.h:222 [inline]
>   rcu_do_batch kernel/rcu/tree.c:2157 [inline]
>   rcu_core+0x630/0x1ca0 kernel/rcu/tree.c:2377
>   __do_softirq+0x221/0x912 kernel/softirq.c:292
>
> The buggy address belongs to the object at ffff8881cf679800
>   which belongs to the cache task_struct of size 5888
> The buggy address is located 32 bytes inside of
>   5888-byte region [ffff8881cf679800, ffff8881cf67af00)
> The buggy address belongs to the page:
> page:ffffea00073d9e00 refcount:1 mapcount:0 mapping:ffff8881da116000
> index:0x0 compound_mapcount: 0
> flags: 0x200000000010200(slab|head)
> raw: 0200000000010200 dead000000000100 dead000000000122 ffff8881da116000
> raw: 0000000000000000 0000000080050005 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>   ffff8881cf679700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>   ffff8881cf679780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> > ffff8881cf679800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                 ^
>   ffff8881cf679880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>   ffff8881cf679900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx
>
> syzbot will keep track of this bug report. See:
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> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches

#syz fix: USB: chaoskey: fix use-after-free on release