Re: KASAN: slab-out-of-bounds Read in hex_string

[Andrey Konovalov]

On Mon, Apr 29, 2019 at 2:06 PM syzbot
<syzbot+a9fefd18c7b240f19c54@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    43151d6c usb-fuzzer: main usb gadget fuzzer driver
> git tree:       https://github.com/google/kasan/tree/usb-fuzzer
> console output: https://syzkaller.appspot.com/x/log.txt?x=139ac37f200000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=4183eeef650d1234
> dashboard link: https://syzkaller.appspot.com/bug?extid=a9fefd18c7b240f19c54
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17f3b338a00000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+a9fefd18c7b240f19c54@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in hex_string+0x418/0x4b0 lib/vsprintf.c:975
> Read of size 1 at addr ffff88821a41bd38 by task kworker/0:1/12
>
> CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.1.0-rc3-319004-g43151d6 #6
> 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+0xe8/0x16e lib/dump_stack.c:113
>   print_address_description+0x6c/0x236 mm/kasan/report.c:187
>   kasan_report.cold+0x1a/0x3c mm/kasan/report.c:317
>   hex_string+0x418/0x4b0 lib/vsprintf.c:975
>   pointer+0x460/0x910 lib/vsprintf.c:1985
>   vsnprintf+0x5a0/0x16b0 lib/vsprintf.c:2400
>   pointer+0x60b/0x910 lib/vsprintf.c:2038
>   vsnprintf+0x5a0/0x16b0 lib/vsprintf.c:2400
>   vscnprintf+0x29/0x80 lib/vsprintf.c:2499
>   vprintk_store+0x45/0x4b0 kernel/printk/printk.c:1900
>   vprintk_emit+0x210/0x5a0 kernel/printk/printk.c:1957
>   dev_vprintk_emit+0x50e/0x553 drivers/base/core.c:3185
>   dev_printk_emit+0xbf/0xf6 drivers/base/core.c:3196
>   __dev_printk+0x1ed/0x215 drivers/base/core.c:3208
>   _dev_info+0xdc/0x10e drivers/base/core.c:3254
>   dlfb_parse_vendor_descriptor drivers/video/fbdev/udlfb.c:1532 [inline]
>   dlfb_usb_probe.cold+0xb96/0x1701 drivers/video/fbdev/udlfb.c:1615
>   usb_probe_interface+0x31d/0x820 drivers/usb/core/driver.c:361
>   really_probe+0x2da/0xb10 drivers/base/dd.c:509
>   driver_probe_device+0x21d/0x350 drivers/base/dd.c:671
>   __device_attach_driver+0x1d8/0x290 drivers/base/dd.c:778
>   bus_for_each_drv+0x163/0x1e0 drivers/base/bus.c:454
>   __device_attach+0x223/0x3a0 drivers/base/dd.c:844
>   bus_probe_device+0x1f1/0x2a0 drivers/base/bus.c:514
>   device_add+0xad2/0x16e0 drivers/base/core.c:2106
>   usb_set_configuration+0xdf7/0x1740 drivers/usb/core/message.c:2023
>   generic_probe+0xa2/0xda drivers/usb/core/generic.c:210
>   usb_probe_device+0xc0/0x150 drivers/usb/core/driver.c:266
>   really_probe+0x2da/0xb10 drivers/base/dd.c:509
>   driver_probe_device+0x21d/0x350 drivers/base/dd.c:671
>   __device_attach_driver+0x1d8/0x290 drivers/base/dd.c:778
>   bus_for_each_drv+0x163/0x1e0 drivers/base/bus.c:454
>   __device_attach+0x223/0x3a0 drivers/base/dd.c:844
>   bus_probe_device+0x1f1/0x2a0 drivers/base/bus.c:514
>   device_add+0xad2/0x16e0 drivers/base/core.c:2106
>   usb_new_device.cold+0x537/0xccf drivers/usb/core/hub.c:2534
>   hub_port_connect drivers/usb/core/hub.c:5089 [inline]
>   hub_port_connect_change drivers/usb/core/hub.c:5204 [inline]
>   port_event drivers/usb/core/hub.c:5350 [inline]
>   hub_event+0x138e/0x3b00 drivers/usb/core/hub.c:5432
>   process_one_work+0x90f/0x1580 kernel/workqueue.c:2269
>   worker_thread+0x9b/0xe20 kernel/workqueue.c:2415
>   kthread+0x313/0x420 kernel/kthread.c:253
>   ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
>
> Allocated by task 12:
>   set_track mm/kasan/common.c:87 [inline]
>   __kasan_kmalloc mm/kasan/common.c:497 [inline]
>   __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:470
>   kmalloc include/linux/slab.h:552 [inline]
>   usb_get_configuration+0x313/0x32b0 drivers/usb/core/config.c:857
>   usb_enumerate_device drivers/usb/core/hub.c:2367 [inline]
>   usb_new_device+0x2fe/0x450 drivers/usb/core/hub.c:2503
>   hub_port_connect drivers/usb/core/hub.c:5089 [inline]
>   hub_port_connect_change drivers/usb/core/hub.c:5204 [inline]
>   port_event drivers/usb/core/hub.c:5350 [inline]
>   hub_event+0x138e/0x3b00 drivers/usb/core/hub.c:5432
>   process_one_work+0x90f/0x1580 kernel/workqueue.c:2269
>   worker_thread+0x9b/0xe20 kernel/workqueue.c:2415
>   kthread+0x313/0x420 kernel/kthread.c:253
>   ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
>
> Freed by task 1464:
>   set_track mm/kasan/common.c:87 [inline]
>   __kasan_slab_free+0x130/0x180 mm/kasan/common.c:459
>   slab_free_hook mm/slub.c:1429 [inline]
>   slab_free_freelist_hook+0x5e/0x140 mm/slub.c:1456
>   slab_free mm/slub.c:3003 [inline]
>   kfree+0xce/0x290 mm/slub.c:3958
>   single_release+0x91/0xb0 fs/seq_file.c:597
>   __fput+0x2df/0x8c0 fs/file_table.c:278
>   task_work_run+0x149/0x1c0 kernel/task_work.c:113
>   tracehook_notify_resume include/linux/tracehook.h:188 [inline]
>   exit_to_usermode_loop+0x243/0x270 arch/x86/entry/common.c:166
>   prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
>   syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
>   do_syscall_64+0x40c/0x4f0 arch/x86/entry/common.c:293
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> The buggy address belongs to the object at ffff88821a41bd20
>   which belongs to the cache kmalloc-32 of size 32
> The buggy address is located 24 bytes inside of
>   32-byte region [ffff88821a41bd20, ffff88821a41bd40)
> The buggy address belongs to the page:
> page:ffffea00086906c0 count:1 mapcount:0 mapping:ffff88812c3f5800 index:0x0
> flags: 0x57ff00000000200(slab)
> raw: 057ff00000000200 dead000000000100 dead000000000200 ffff88812c3f5800
> raw: 0000000000000000 0000000000550055 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>   ffff88821a41bc00: 00 00 00 fc fc fc 00 00 00 00 fc fc 00 00 00 00
>   ffff88821a41bc80: fc fc 00 00 00 00 fc fc fb fb fb fb fc fc fb fb
> > ffff88821a41bd00: fb fb fc fc 00 00 00 fc fc fc fb fb fb fb fc fc
>                                          ^
>   ffff88821a41bd80: 00 00 00 fc fc fc 00 00 00 fc fc fc fb fb fb fb
>   ffff88821a41be00: fc fc fb fb fb fb fc fc fb fb fb fb fc fc 00 00
> ==================================================================
>
>
> ---
> 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 dup: KASAN: slab-out-of-bounds Read in dlfb_usb_probe