Re: KASAN: use-after-free Write in v4l2_prio_close

[Andrey Konovalov]

On Mon, Jun 3, 2019 at 1:41 PM syzbot
<syzbot+a6566701042e6e3e4ed1@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    69bbe8c7 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=142ef636a00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=193d8457178b3229
> dashboard link: https://syzkaller.appspot.com/bug?extid=a6566701042e6e3e4ed1
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+a6566701042e6e3e4ed1@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> ==================================================================
> BUG: KASAN: use-after-free in atomic_dec
> include/asm-generic/atomic-instrumented.h:329 [inline]
> BUG: KASAN: use-after-free in v4l2_prio_close+0x45/0x60
> drivers/media/v4l2-core/v4l2-dev.c:285
> Write of size 4 at addr ffff8881d4d21890 by task v4l_id/3238
>
> CPU: 1 PID: 3238 Comm: v4l_id Not tainted 5.2.0-rc1+ #10
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0xca/0x13e lib/dump_stack.c:113
>   print_address_description+0x67/0x231 mm/kasan/report.c:188
>   __kasan_report.cold+0x1a/0x32 mm/kasan/report.c:317
>   kasan_report+0xe/0x20 mm/kasan/common.c:614
>   atomic_dec include/asm-generic/atomic-instrumented.h:329 [inline]
>   v4l2_prio_close+0x45/0x60 drivers/media/v4l2-core/v4l2-dev.c:285
>   v4l2_fh_release+0x41/0x70 drivers/media/v4l2-core/v4l2-fh.c:104
>   v4l2_release+0x2e7/0x390 drivers/media/v4l2-core/v4l2-dev.c:459
>   __fput+0x2d7/0x790 fs/file_table.c:279
>   task_work_run+0x13f/0x1c0 kernel/task_work.c:113
>   tracehook_notify_resume include/linux/tracehook.h:188 [inline]
>   exit_to_usermode_loop+0x1c5/0x1f0 arch/x86/entry/common.c:168
>   prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
>   syscall_return_slowpath arch/x86/entry/common.c:279 [inline]
>   do_syscall_64+0x43f/0x560 arch/x86/entry/common.c:304
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x7f5bcbde22b0
> Code: 40 75 0b 31 c0 48 83 c4 08 e9 0c ff ff ff 48 8d 3d c5 32 08 00 e8 c0
> 07 02 00 83 3d 45 a3 2b 00 00 75 10 b8 03 00 00 00 0f 05 <48> 3d 01 f0 ff
> ff 73 31 c3 48 83 ec 08 e8 ce 8a 01 00 48 89 04 24
> RSP: 002b:00007ffd54ae7938 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
> RAX: 0000000000000000 RBX: 0000000000000003 RCX: 00007f5bcbde22b0
> RDX: 0000000000000013 RSI: 0000000080685600 RDI: 0000000000000003
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000400884
> R13: 00007ffd54ae7a90 R14: 0000000000000000 R15: 0000000000000000
>
> Allocated by task 2762:
>   save_stack+0x1b/0x80 mm/kasan/common.c:71
>   set_track mm/kasan/common.c:79 [inline]
>   __kasan_kmalloc mm/kasan/common.c:489 [inline]
>   __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:462
>   slab_post_alloc_hook mm/slab.h:437 [inline]
>   slab_alloc_node mm/slub.c:2748 [inline]
>   __kmalloc_node_track_caller+0xee/0x370 mm/slub.c:4363
>   alloc_dr drivers/base/devres.c:103 [inline]
>   devm_kmalloc+0x87/0x190 drivers/base/devres.c:793
>   devm_kzalloc include/linux/device.h:679 [inline]
>   usb_raremono_probe+0x2f/0x231 drivers/media/radio/radio-raremono.c:298
>   usb_probe_interface+0x305/0x7a0 drivers/usb/core/driver.c:361
>   really_probe+0x281/0x660 drivers/base/dd.c:509
>   driver_probe_device+0x104/0x210 drivers/base/dd.c:670
>   __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:777
>   bus_for_each_drv+0x15c/0x1e0 drivers/base/bus.c:454
>   __device_attach+0x217/0x360 drivers/base/dd.c:843
>   bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
>   device_add+0xae6/0x16f0 drivers/base/core.c:2111
>   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+0x281/0x660 drivers/base/dd.c:509
>   driver_probe_device+0x104/0x210 drivers/base/dd.c:670
>   __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:777
>   bus_for_each_drv+0x15c/0x1e0 drivers/base/bus.c:454
>   __device_attach+0x217/0x360 drivers/base/dd.c:843
>   bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
>   device_add+0xae6/0x16f0 drivers/base/core.c:2111
>   usb_new_device.cold+0x8c1/0x1016 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+0x1ada/0x3590 drivers/usb/core/hub.c:5432
>   process_one_work+0x905/0x1570 kernel/workqueue.c:2268
>   process_scheduled_works kernel/workqueue.c:2330 [inline]
>   worker_thread+0x7ab/0xe20 kernel/workqueue.c:2416
>   kthread+0x30b/0x410 kernel/kthread.c:254
>   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
>
> Freed by task 2762:
>   save_stack+0x1b/0x80 mm/kasan/common.c:71
>   set_track mm/kasan/common.c:79 [inline]
>   __kasan_slab_free+0x130/0x180 mm/kasan/common.c:451
>   slab_free_hook mm/slub.c:1421 [inline]
>   slab_free_freelist_hook mm/slub.c:1448 [inline]
>   slab_free mm/slub.c:2994 [inline]
>   kfree+0xd7/0x280 mm/slub.c:3949
>   release_nodes+0x4a1/0x910 drivers/base/devres.c:508
>   devres_release_all+0x74/0xc3 drivers/base/devres.c:529
>   __device_release_driver drivers/base/dd.c:1085 [inline]
>   device_release_driver_internal+0x21b/0x4c0 drivers/base/dd.c:1112
>   bus_remove_device+0x2dc/0x4a0 drivers/base/bus.c:556
>   device_del+0x460/0xb80 drivers/base/core.c:2274
>   usb_disable_device+0x211/0x690 drivers/usb/core/message.c:1237
>   usb_disconnect+0x284/0x830 drivers/usb/core/hub.c:2197
>   hub_port_connect drivers/usb/core/hub.c:4940 [inline]
>   hub_port_connect_change drivers/usb/core/hub.c:5204 [inline]
>   port_event drivers/usb/core/hub.c:5350 [inline]
>   hub_event+0x1409/0x3590 drivers/usb/core/hub.c:5432
>   process_one_work+0x905/0x1570 kernel/workqueue.c:2268
>   process_scheduled_works kernel/workqueue.c:2330 [inline]
>   worker_thread+0x7ab/0xe20 kernel/workqueue.c:2416
>   kthread+0x30b/0x410 kernel/kthread.c:254
>   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
>
> The buggy address belongs to the object at ffff8881d4d21100
>   which belongs to the cache kmalloc-4k of size 4096
> The buggy address is located 1936 bytes inside of
>   4096-byte region [ffff8881d4d21100, ffff8881d4d22100)
> The buggy address belongs to the page:
> page:ffffea0007534800 refcount:1 mapcount:0 mapping:ffff8881dac02600
> index:0x0 compound_mapcount: 0
> flags: 0x200000000010200(slab|head)
> raw: 0200000000010200 dead000000000100 dead000000000200 ffff8881dac02600
> raw: 0000000000000000 0000000000070007 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>   ffff8881d4d21780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>   ffff8881d4d21800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ffff8881d4d21880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                           ^
>   ffff8881d4d21900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>   ffff8881d4d21980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================

#syz dup: KASAN: use-after-free Read in v4l2_ioctl

>
>
> ---
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