Re: KASAN: use-after-free Read in idr_for_each (2)

From: syzbot
Date: Fri Dec 18 2020 - 11:45:01 EST

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Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: use-after-free Read in idr_for_each

==================================================================
BUG: KASAN: use-after-free in radix_tree_next_slot include/linux/radix-tree.h:422 [inline]
BUG: KASAN: use-after-free in idr_for_each+0x206/0x220 lib/idr.c:202
Read of size 8 at addr ffff888042e76040 by task kworker/u4:5/3340

CPU: 0 PID: 3340 Comm: kworker/u4:5 Not tainted 5.10.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_unbound io_ring_exit_work
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x107/0x163 lib/dump_stack.c:120
print_address_description.constprop.0.cold+0xae/0x4c8 mm/kasan/report.c:385
__kasan_report mm/kasan/report.c:545 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:562
radix_tree_next_slot include/linux/radix-tree.h:422 [inline]
idr_for_each+0x206/0x220 lib/idr.c:202
io_destroy_buffers fs/io_uring.c:8541 [inline]
io_ring_ctx_free fs/io_uring.c:8564 [inline]
io_ring_exit_work+0x394/0x730 fs/io_uring.c:8639
process_one_work+0x98d/0x1630 kernel/workqueue.c:2275
worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
kthread+0x3b1/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Allocated by task 28625:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:461
slab_post_alloc_hook mm/slab.h:512 [inline]
slab_alloc_node mm/slub.c:2889 [inline]
slab_alloc mm/slub.c:2897 [inline]
kmem_cache_alloc+0x145/0x350 mm/slub.c:2902
radix_tree_node_alloc.constprop.0+0x7c/0x350 lib/radix-tree.c:274
idr_get_free+0x554/0xa60 lib/radix-tree.c:1504
idr_alloc_u32+0x170/0x2d0 lib/idr.c:46
idr_alloc+0xc2/0x130 lib/idr.c:87
io_provide_buffers fs/io_uring.c:4230 [inline]
io_issue_sqe+0x3681/0x44e0 fs/io_uring.c:6264
__io_queue_sqe+0x228/0x1120 fs/io_uring.c:6477
io_queue_sqe+0x631/0x10f0 fs/io_uring.c:6543
io_submit_sqe fs/io_uring.c:6616 [inline]
io_submit_sqes+0x135a/0x2530 fs/io_uring.c:6864
__do_sys_io_uring_enter+0x591/0x1c00 fs/io_uring.c:9174
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 8890:
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:352
__kasan_slab_free+0x102/0x140 mm/kasan/common.c:422
slab_free_hook mm/slub.c:1544 [inline]
slab_free_freelist_hook+0x5d/0x150 mm/slub.c:1577
slab_free mm/slub.c:3140 [inline]
kmem_cache_free+0x82/0x360 mm/slub.c:3156
rcu_do_batch kernel/rcu/tree.c:2489 [inline]
rcu_core+0x75d/0xf80 kernel/rcu/tree.c:2723
__do_softirq+0x2bc/0xa77 kernel/softirq.c:343

Last potentially related work creation:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_record_aux_stack+0xc0/0xf0 mm/kasan/generic.c:343
__call_rcu kernel/rcu/tree.c:2965 [inline]
call_rcu+0xbb/0x710 kernel/rcu/tree.c:3038
radix_tree_node_free lib/radix-tree.c:308 [inline]
delete_node+0x591/0x8c0 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
__io_remove_buffers fs/io_uring.c:4122 [inline]
__io_remove_buffers fs/io_uring.c:4101 [inline]
__io_destroy_buffers+0x161/0x200 fs/io_uring.c:8535
idr_for_each+0x113/0x220 lib/idr.c:208
io_destroy_buffers fs/io_uring.c:8541 [inline]
io_ring_ctx_free fs/io_uring.c:8564 [inline]
io_ring_exit_work+0x394/0x730 fs/io_uring.c:8639
process_one_work+0x98d/0x1630 kernel/workqueue.c:2275
worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
kthread+0x3b1/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Second to last potentially related work creation:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_record_aux_stack+0xc0/0xf0 mm/kasan/generic.c:343
__call_rcu kernel/rcu/tree.c:2965 [inline]
call_rcu+0xbb/0x710 kernel/rcu/tree.c:3038
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+0xbeb/0x1c10 lib/xarray.c:841
__xa_erase lib/xarray.c:1489 [inline]
xa_erase+0xb0/0x170 lib/xarray.c:1510
io_uring_del_task_file fs/io_uring.c:8889 [inline]
__io_uring_files_cancel+0xdbf/0x1550 fs/io_uring.c:8925
io_uring_files_cancel include/linux/io_uring.h:51 [inline]
exit_files+0xe4/0x170 fs/file.c:431
do_exit+0xb4f/0x2a00 kernel/exit.c:818
do_group_exit+0x125/0x310 kernel/exit.c:920
get_signal+0x3e9/0x2160 kernel/signal.c:2770
arch_do_signal_or_restart+0x2a8/0x1eb0 arch/x86/kernel/signal.c:811
handle_signal_work kernel/entry/common.c:147 [inline]
exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
exit_to_user_mode_prepare+0x124/0x200 kernel/entry/common.c:201
__syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:302
entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff888042e76000
which belongs to the cache radix_tree_node of size 576
The buggy address is located 64 bytes inside of
576-byte region [ffff888042e76000, ffff888042e76240)
The buggy address belongs to the page:
page:0000000090e8be83 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x42e76
head:0000000090e8be83 order:1 compound_mapcount:0
flags: 0xfff00000010200(slab|head)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff88801084db40
raw: ffff888042e76580 00000000800b000a 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888042e75f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888042e75f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888042e76000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888042e76080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888042e76100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Tested on:

commit: dfea9fce io_uring: close a small race gap for files cancel
git tree: git://git.kernel.dk/linux-block
console output: https://syzkaller.appspot.com/x/log.txt?x=1263a46b500000
kernel config: https://syzkaller.appspot.com/x/.config?x=4db50a97037d9f3e
dashboard link: https://syzkaller.appspot.com/bug?extid=12056a09a0311d758e60
compiler: gcc (GCC) 10.1.0-syz 20200507

Next message: Daniel Thompson: "Re: [PATCH] x86/kgdb: Allow removal of early BPs"
Previous message: Pavel Begunkov: "Re: WARNING in percpu_ref_kill_and_confirm (2)"
In reply to: Pavel Begunkov: "Re: KASAN: use-after-free Read in idr_for_each (2)"
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