syzbot

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BUG: KASAN: use-after-free in xas_next_entry include/linux/xarray.h:1630 [inline]
BUG: KASAN: use-after-free in __io_uring_files_cancel+0x417/0x440 fs/io_uring.c:8680
Read of size 1 at addr ffff88806d84fbc0 by task syz-executor.0/8287

CPU: 0 PID: 8287 Comm: syz-executor.0 Not tainted 5.9.0-rc8-next-20201009-syzkaller #0
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+0x198/0x1fb lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:385
 __kasan_report mm/kasan/report.c:545 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:562
 xas_next_entry include/linux/xarray.h:1630 [inline]
 __io_uring_files_cancel+0x417/0x440 fs/io_uring.c:8680
 io_uring_files_cancel include/linux/io_uring.h:35 [inline]
 exit_files+0xe4/0x170 fs/file.c:456
 do_exit+0xae9/0x2930 kernel/exit.c:801
 do_group_exit+0x125/0x310 kernel/exit.c:903
 get_signal+0x428/0x1f00 kernel/signal.c:2757
 arch_do_signal+0x82/0x2470 arch/x86/kernel/signal.c:811
 exit_to_user_mode_loop kernel/entry/common.c:161 [inline]
 exit_to_user_mode_prepare+0x1b1/0x210 kernel/entry/common.c:192
 syscall_exit_to_user_mode+0x7a/0x2c0 kernel/entry/common.c:267
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45de59
Code: Unable to access opcode bytes at RIP 0x45de2f.
RSP: 002b:00007faf8b3cebf8 EFLAGS: 00000206 ORIG_RAX: 00000000000001a9
RAX: fffffffffffffffc RBX: 0000000020000000 RCX: 000000000045de59
RDX: 0000000020ffe000 RSI: 0000000020000000 RDI: 0000000000001c28
RBP: 000000000118bf78 R08: 00000000200000c0 R09: 00000000200000c0
R10: 0000000020000080 R11: 0000000000000206 R12: 0000000020ffe000
R13: 0000000020fff000 R14: 00000000200000c0 R15: 0000000020000080

Allocated by task 8287:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
 slab_post_alloc_hook mm/slab.h:514 [inline]
 slab_alloc mm/slab.c:3314 [inline]
 kmem_cache_alloc+0x162/0x550 mm/slab.c:3484
 xas_alloc+0x330/0x440 lib/xarray.c:374
 xas_create+0x2db/0x1020 lib/xarray.c:676
 xas_store+0x8a/0x1bb0 lib/xarray.c:784
 io_uring_add_task_file fs/io_uring.c:8607 [inline]
 io_uring_add_task_file+0x212/0x430 fs/io_uring.c:8589
 io_uring_get_fd fs/io_uring.c:9115 [inline]
 io_uring_create fs/io_uring.c:9279 [inline]
 io_uring_setup+0x2727/0x3660 fs/io_uring.c:9313
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 6909:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track+0x1c/0x30 mm/kasan/common.c:56
 kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355
 __kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422
 __cache_free mm/slab.c:3420 [inline]
 kmem_cache_free.part.0+0x74/0x1d0 mm/slab.c:3695
 rcu_do_batch kernel/rcu/tree.c:2484 [inline]
 rcu_core+0x645/0x1240 kernel/rcu/tree.c:2718
 __do_softirq+0x203/0xac5 kernel/softirq.c:298

Last call_rcu():
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_record_aux_stack+0x82/0xb0 mm/kasan/generic.c:346
 __call_rcu kernel/rcu/tree.c:2960 [inline]
 call_rcu+0x15e/0x7d0 kernel/rcu/tree.c:3033
 xa_node_free lib/xarray.c:258 [inline]
 xas_delete_node lib/xarray.c:494 [inline]
 update_node lib/xarray.c:756 [inline]
 xas_store+0xbcc/0x1bb0 lib/xarray.c:841
 io_uring_del_task_file+0x105/0x1a0 fs/io_uring.c:8629
 __io_uring_files_cancel+0x3dd/0x440 fs/io_uring.c:8690
 io_uring_files_cancel include/linux/io_uring.h:35 [inline]
 exit_files+0xe4/0x170 fs/file.c:456
 do_exit+0xae9/0x2930 kernel/exit.c:801
 do_group_exit+0x125/0x310 kernel/exit.c:903
 get_signal+0x428/0x1f00 kernel/signal.c:2757
 arch_do_signal+0x82/0x2470 arch/x86/kernel/signal.c:811
 exit_to_user_mode_loop kernel/entry/common.c:161 [inline]
 exit_to_user_mode_prepare+0x1b1/0x210 kernel/entry/common.c:192
 syscall_exit_to_user_mode+0x7a/0x2c0 kernel/entry/common.c:267
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff88806d84fbc0
 which belongs to the cache radix_tree_node of size 576
The buggy address is located 0 bytes inside of
 576-byte region [ffff88806d84fbc0, ffff88806d84fe00)
The buggy address belongs to the page:
page:00000000e0aecccb refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88806d84fffb pfn:0x6d84f
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0001b61388 ffffea0001b62ac8 ffff88800ec6f000
raw: ffff88806d84fffb ffff88806d84f0c0 0000000100000005 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88806d84fa80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88806d84fb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88806d84fb80: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
                                           ^
 ffff88806d84fc00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88806d84fc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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