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BUG: KASAN: use-after-free in p9_conn_cancel+0x3f3/0x4c0 net/9p/trans_fd.c:203
Read of size 4 at addr ffff8801cb86b928 by task kworker/0:2/1838

CPU: 0 PID: 1838 Comm: kworker/0:2 Not tainted 4.9.111-g03c70fe #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events p9_poll_workfn
 ffff8801ce247aa0 ffffffff81eb2729 ffffea00072e1a80 ffff8801cb86b928
 0000000000000000 ffff8801cb86b928 00000000ffffff87 ffff8801ce247ad8
 ffffffff81567b59 ffff8801cb86b928 0000000000000004 0000000000000000
Call Trace:
 [<ffffffff81eb2729>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb2729>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81567b59>] print_address_description+0x6c/0x234 mm/kasan/report.c:256
 [<ffffffff81567f63>] kasan_report_error mm/kasan/report.c:355 [inline]
 [<ffffffff81567f63>] kasan_report.cold.6+0x242/0x2fe mm/kasan/report.c:412
 [<ffffffff8153bb94>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
 [<ffffffff839c1c23>] p9_conn_cancel+0x3f3/0x4c0 net/9p/trans_fd.c:203
 [<ffffffff839c2242>] p9_poll_mux net/9p/trans_fd.c:630 [inline]
 [<ffffffff839c2242>] p9_poll_workfn+0x222/0x330 net/9p/trans_fd.c:1097
 [<ffffffff8118d131>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118df26>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119d05d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f8e9c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373

Allocated by task 3913:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 save_stack+0x43/0xd0 mm/kasan/kasan.c:505
 set_track mm/kasan/kasan.c:517 [inline]
 kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:609
 kmem_cache_alloc_trace+0xfd/0x2b0 mm/slub.c:2742
 kmalloc include/linux/slab.h:490 [inline]
 kzalloc include/linux/slab.h:636 [inline]
 p9_fd_open net/9p/trans_fd.c:792 [inline]
 p9_fd_create+0xf3/0x330 net/9p/trans_fd.c:1029
 p9_client_create+0x6ff/0x10a0 net/9p/client.c:1036
 v9fs_session_init+0x333/0x13a0 fs/9p/v9fs.c:343
 v9fs_mount+0x7d/0x810 fs/9p/vfs_super.c:130
 mount_fs+0x28c/0x370 fs/super.c:1206
 vfs_kern_mount.part.29+0xd1/0x3d0 fs/namespace.c:991
 vfs_kern_mount fs/namespace.c:973 [inline]
 do_new_mount fs/namespace.c:2513 [inline]
 do_mount+0x3c9/0x2740 fs/namespace.c:2835
 C_SYSC_mount fs/compat.c:810 [inline]
 compat_SyS_mount+0x4fc/0xff0 fs/compat.c:775
 do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline]
 do_fast_syscall_32+0x2f7/0x870 arch/x86/entry/common.c:387
 entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137

Freed by task 3913:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 save_stack+0x43/0xd0 mm/kasan/kasan.c:505
 set_track mm/kasan/kasan.c:517 [inline]
 kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:582
 slab_free_hook mm/slub.c:1355 [inline]
 slab_free_freelist_hook mm/slub.c:1377 [inline]
 slab_free mm/slub.c:2958 [inline]
 kfree+0xfb/0x310 mm/slub.c:3878
 p9_fd_close+0x298/0x330 net/9p/trans_fd.c:890
 p9_client_destroy+0x73/0x570 net/9p/client.c:1070
 v9fs_session_close+0x46/0x110 fs/9p/v9fs.c:434
 v9fs_kill_super+0x4e/0xa0 fs/9p/vfs_super.c:226
 deactivate_locked_super+0x75/0xd0 fs/super.c:310
 v9fs_mount+0x3c6/0x810 fs/9p/vfs_super.c:207
 mount_fs+0x28c/0x370 fs/super.c:1206
 vfs_kern_mount.part.29+0xd1/0x3d0 fs/namespace.c:991
 vfs_kern_mount fs/namespace.c:973 [inline]
 do_new_mount fs/namespace.c:2513 [inline]
 do_mount+0x3c9/0x2740 fs/namespace.c:2835
 C_SYSC_mount fs/compat.c:810 [inline]
 compat_SyS_mount+0x4fc/0xff0 fs/compat.c:775
 do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline]
 do_fast_syscall_32+0x2f7/0x870 arch/x86/entry/common.c:387
 entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137

The buggy address belongs to the object at ffff8801cb86b900
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 40 bytes inside of
 512-byte region [ffff8801cb86b900, ffff8801cb86bb00)
The buggy address belongs to the page:
page:ffffea00072e1a80 count:1 mapcount:0 mapping:          (null) index:0x0 compound_mapcount: 0
flags: 0x8000000000004080(slab|head)
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801cb86b800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801cb86b880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801cb86b900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff8801cb86b980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801cb86ba00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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