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    SubjectKASAN: use-after-free Read in appledisplay_bl_get_brightness
    From
    Hello,

    syzbot found the following crash on:

    HEAD commit: e0bd8d79 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=13714ad9600000
    kernel config: https://syzkaller.appspot.com/x/.config?x=8847e5384a16f66a
    dashboard link: https://syzkaller.appspot.com/bug?extid=495dab1f175edc9c2f13
    compiler: gcc (GCC) 9.0.0 20181231 (experimental)
    syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1653d945600000
    C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15176945600000

    IMPORTANT: if you fix the bug, please add the following tag to the commit:
    Reported-by: syzbot+495dab1f175edc9c2f13@syzkaller.appspotmail.com

    ==================================================================
    BUG: KASAN: use-after-free in appledisplay_bl_get_brightness+0x1ac/0x1c0
    drivers/usb/misc/appledisplay.c:167
    Read of size 8 at addr ffff8881cfc576a0 by task kworker/1:0/17

    CPU: 1 PID: 17 Comm: kworker/1:0 Not tainted 5.3.0+ #0
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
    Google 01/01/2011
    Workqueue: events appledisplay_work
    Call Trace:
    __dump_stack lib/dump_stack.c:77 [inline]
    dump_stack+0xca/0x13e lib/dump_stack.c:113
    print_address_description+0x6a/0x32c mm/kasan/report.c:351
    __kasan_report.cold+0x1a/0x33 mm/kasan/report.c:482
    kasan_report+0xe/0x12 mm/kasan/common.c:618
    appledisplay_bl_get_brightness+0x1ac/0x1c0
    drivers/usb/misc/appledisplay.c:167
    appledisplay_work+0x36/0x160 drivers/usb/misc/appledisplay.c:187
    process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
    worker_thread+0x96/0xe20 kernel/workqueue.c:2415
    kthread+0x318/0x420 kernel/kthread.c:255
    ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

    Allocated by task 83:
    save_stack+0x1b/0x80 mm/kasan/common.c:69
    set_track mm/kasan/common.c:77 [inline]
    __kasan_kmalloc mm/kasan/common.c:493 [inline]
    __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:466
    kmalloc include/linux/slab.h:552 [inline]
    kzalloc include/linux/slab.h:748 [inline]
    appledisplay_probe+0x15a/0xb37 drivers/usb/misc/appledisplay.c:218
    usb_probe_interface+0x305/0x7a0 drivers/usb/core/driver.c:361
    really_probe+0x281/0x6d0 drivers/base/dd.c:548
    driver_probe_device+0x101/0x1b0 drivers/base/dd.c:721
    __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
    bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:430
    __device_attach+0x217/0x360 drivers/base/dd.c:894
    bus_probe_device+0x1e4/0x290 drivers/base/bus.c:490
    device_add+0xae6/0x16f0 drivers/base/core.c:2201
    usb_set_configuration+0xdf6/0x1670 drivers/usb/core/message.c:2023
    generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210
    usb_probe_device+0x99/0x100 drivers/usb/core/driver.c:266
    really_probe+0x281/0x6d0 drivers/base/dd.c:548
    driver_probe_device+0x101/0x1b0 drivers/base/dd.c:721
    __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
    bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:430
    __device_attach+0x217/0x360 drivers/base/dd.c:894
    bus_probe_device+0x1e4/0x290 drivers/base/bus.c:490
    device_add+0xae6/0x16f0 drivers/base/core.c:2201
    usb_new_device.cold+0x6a4/0xe79 drivers/usb/core/hub.c:2536
    hub_port_connect drivers/usb/core/hub.c:5098 [inline]
    hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
    port_event drivers/usb/core/hub.c:5359 [inline]
    hub_event+0x1b5c/0x3640 drivers/usb/core/hub.c:5441
    process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
    worker_thread+0x96/0xe20 kernel/workqueue.c:2415
    kthread+0x318/0x420 kernel/kthread.c:255
    ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

    Freed by task 83:
    save_stack+0x1b/0x80 mm/kasan/common.c:69
    set_track mm/kasan/common.c:77 [inline]
    __kasan_slab_free+0x130/0x180 mm/kasan/common.c:455
    slab_free_hook mm/slub.c:1423 [inline]
    slab_free_freelist_hook mm/slub.c:1474 [inline]
    slab_free mm/slub.c:3016 [inline]
    kfree+0xe4/0x2f0 mm/slub.c:3957
    appledisplay_probe+0x772/0xb37 drivers/usb/misc/appledisplay.c:312
    usb_probe_interface+0x305/0x7a0 drivers/usb/core/driver.c:361
    really_probe+0x281/0x6d0 drivers/base/dd.c:548
    driver_probe_device+0x101/0x1b0 drivers/base/dd.c:721
    __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
    bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:430
    __device_attach+0x217/0x360 drivers/base/dd.c:894
    bus_probe_device+0x1e4/0x290 drivers/base/bus.c:490
    device_add+0xae6/0x16f0 drivers/base/core.c:2201
    usb_set_configuration+0xdf6/0x1670 drivers/usb/core/message.c:2023
    generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210
    usb_probe_device+0x99/0x100 drivers/usb/core/driver.c:266
    really_probe+0x281/0x6d0 drivers/base/dd.c:548
    driver_probe_device+0x101/0x1b0 drivers/base/dd.c:721
    __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
    bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:430
    __device_attach+0x217/0x360 drivers/base/dd.c:894
    bus_probe_device+0x1e4/0x290 drivers/base/bus.c:490
    device_add+0xae6/0x16f0 drivers/base/core.c:2201
    usb_new_device.cold+0x6a4/0xe79 drivers/usb/core/hub.c:2536
    hub_port_connect drivers/usb/core/hub.c:5098 [inline]
    hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
    port_event drivers/usb/core/hub.c:5359 [inline]
    hub_event+0x1b5c/0x3640 drivers/usb/core/hub.c:5441
    process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
    worker_thread+0x96/0xe20 kernel/workqueue.c:2415
    kthread+0x318/0x420 kernel/kthread.c:255
    ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

    The buggy address belongs to the object at ffff8881cfc57680
    which belongs to the cache kmalloc-512 of size 512
    The buggy address is located 32 bytes inside of
    512-byte region [ffff8881cfc57680, ffff8881cfc57880)
    The buggy address belongs to the page:
    page:ffffea00073f1580 refcount:1 mapcount:0 mapping:ffff8881da002500
    index:0x0 compound_mapcount: 0
    flags: 0x200000000010200(slab|head)
    raw: 0200000000010200 dead000000000100 dead000000000122 ffff8881da002500
    raw: 0000000000000000 00000000000c000c 00000001ffffffff 0000000000000000
    page dumped because: kasan: bad access detected

    Memory state around the buggy address:
    ffff8881cfc57580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    ffff8881cfc57600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
    > ffff8881cfc57680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    ^
    ffff8881cfc57700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
    ffff8881cfc57780: 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@googlegroups.com.

    syzbot will keep track of this bug report. See:
    https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
    syzbot can test patches for this bug, for details see:
    https://goo.gl/tpsmEJ#testing-patches

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      Last update: 2019-09-23 16:32    [W:2.998 / U:0.076 seconds]
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