KASAN: use-after-free Read in __io_uring_files_cancel

From: syzbot
Date: Fri Oct 09 2020 - 04:02:47 EST

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Hello,

syzbot found the following issue on:

HEAD commit: e4fb79c7 Add linux-next specific files for 20201008
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1592ee1b900000
kernel config: https://syzkaller.appspot.com/x/.config?x=568d41fe4341ed0f
dashboard link: https://syzkaller.appspot.com/bug?extid=77efce558b2b9e6b6405
compiler: gcc (GCC) 10.1.0-syz 20200507

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+77efce558b2b9e6b6405@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
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:8681
Read of size 1 at addr ffff888033631880 by task syz-executor.1/8477

CPU: 1 PID: 8477 Comm: syz-executor.1 Not tainted 5.9.0-rc8-next-20201008-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:8681
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+0x194/0x1f0 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: 0033:0x45de29
Code: Unable to access opcode bytes at RIP 0x45ddff.
RSP: 002b:00007f887aa8fcf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000118bf28 RCX: 000000000045de29
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000118bf28
RBP: 000000000118bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bf2c
R13: 00007ffe3a42135f R14: 00007f887aa909c0 R15: 000000000118bf2c

Allocated by task 8477:
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:8608 [inline]
io_uring_add_task_file+0x212/0x430 fs/io_uring.c:8590
io_uring_get_fd fs/io_uring.c:9116 [inline]
io_uring_create fs/io_uring.c:9280 [inline]
io_uring_setup+0x2727/0x3660 fs/io_uring.c:9314
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 6907:
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+0x203/0xab6 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:8630
__io_uring_files_cancel+0x3dd/0x440 fs/io_uring.c:8691
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+0x194/0x1f0 kernel/entry/common.c:192
syscall_exit_to_user_mode+0x7a/0x2c0 kernel/entry/common.c:267
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Second to 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
radix_tree_node_free lib/radix-tree.c:308 [inline]
delete_node+0xef/0x8c0 lib/radix-tree.c:571
__radix_tree_delete+0x190/0x370 lib/radix-tree.c:1377
radix_tree_delete_item+0xe7/0x230 lib/radix-tree.c:1428
free_pid+0x9b/0x260 kernel/pid.c:152
__change_pid+0x1c7/0x2d0 kernel/pid.c:353
__unhash_process kernel/exit.c:76 [inline]
__exit_signal kernel/exit.c:147 [inline]
release_task+0xd1c/0x14d0 kernel/exit.c:198
exit_notify kernel/exit.c:681 [inline]
do_exit+0x143f/0x2930 kernel/exit.c:826
call_usermodehelper_exec_async+0x413/0x580 kernel/umh.c:123
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

The buggy address belongs to the object at ffff888033631880
which belongs to the cache radix_tree_node of size 576
The buggy address is located 0 bytes inside of
576-byte region [ffff888033631880, ffff888033631ac0)
The buggy address belongs to the page:
page:00000000c45adbd1 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888033631ffb pfn:0x33631
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0000cd8908 ffffea0000cd8488 ffff88800ec6f000
raw: ffff888033631ffb ffff888033631040 0000000100000005 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888033631780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888033631800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888033631880: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888033631900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888033631980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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Next message: tip-bot2 for Alexander A. Klimov: "[tip: locking/core] Replace HTTP links with HTTPS ones: LKMM"
Previous message: tip-bot2 for Marco Elver: "[tip: locking/core] bitops, kcsan: Partially revert instrumentation for non-atomic bitops"
Next in thread: Pavel Begunkov: "Re: KASAN: use-after-free Read in __io_uring_files_cancel"
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