KASAN: use-after-free Read in idr_for_each

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fb893de3 Merge tag 'tag-chrome-platform-for-v5.9' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=167ed216900000
kernel config: https://syzkaller.appspot.com/x/.config?x=f1fedc63022bf07e
dashboard link: https://syzkaller.appspot.com/bug?extid=25d82ed5cc4b474f1df8
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=107bc222900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17a09d06900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+25d82e...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in radix_tree_next_slot include/linux/radix-tree.h:421 [inline]
BUG: KASAN: use-after-free in idr_for_each+0x206/0x220 lib/idr.c:202
Read of size 8 at addr ffff888082058c78 by task syz-executor999/3765

CPU: 1 PID: 3765 Comm: syz-executor999 Not tainted 5.8.0-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+0x18f/0x20d lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
radix_tree_next_slot include/linux/radix-tree.h:421 [inline]
idr_for_each+0x206/0x220 lib/idr.c:202
io_ring_ctx_wait_and_kill+0x374/0x600 fs/io_uring.c:7810
io_uring_release+0x3e/0x50 fs/io_uring.c:7829
__fput+0x285/0x920 fs/file_table.c:281
task_work_run+0xdd/0x190 kernel/task_work.c:135
exit_task_work include/linux/task_work.h:25 [inline]
do_exit+0xb7d/0x29f0 kernel/exit.c:806
do_group_exit+0x125/0x310 kernel/exit.c:903
get_signal+0x40b/0x1ee0 kernel/signal.c:2743
arch_do_signal+0x82/0x2520 arch/x86/kernel/signal.c:811
exit_to_user_mode_loop kernel/entry/common.c:135 [inline]
exit_to_user_mode_prepare+0x172/0x1d0 kernel/entry/common.c:166
syscall_exit_to_user_mode+0x59/0x2b0 kernel/entry/common.c:241
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x447179
Code: Bad RIP value.
RSP: 002b:00007f049661dcf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00000000006dbc38 RCX: 0000000000447179
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00000000006dbc38
RBP: 00000000006dbc30 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc3c
R13: 00007ffd1e2340df R14: 00007f049661e9c0 R15: 0000000000000001

Allocated by task 3747:
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:518 [inline]
slab_alloc mm/slab.c:3312 [inline]
kmem_cache_alloc+0x138/0x3a0 mm/slab.c:3482
radix_tree_node_alloc.constprop.0+0x7c/0x320 lib/radix-tree.c:275
idr_get_free+0x4b0/0x8e0 lib/radix-tree.c:1505
idr_alloc_u32+0x170/0x2d0 lib/idr.c:46
idr_alloc_cyclic+0x102/0x230 lib/idr.c:125
io_register_personality fs/io_uring.c:8454 [inline]
__io_uring_register fs/io_uring.c:8575 [inline]
__do_sys_io_uring_register+0x606/0x33f0 fs/io_uring.c:8615
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 16:
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:3418 [inline]
kmem_cache_free.part.0+0x67/0x1f0 mm/slab.c:3693
rcu_do_batch kernel/rcu/tree.c:2428 [inline]
rcu_core+0x5c7/0x1190 kernel/rcu/tree.c:2656
__do_softirq+0x2de/0xa24 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:2894 [inline]
call_rcu+0x14f/0x7e0 kernel/rcu/tree.c:2968
radix_tree_node_free lib/radix-tree.c:309 [inline]
delete_node+0x587/0x8a0 lib/radix-tree.c:572
__radix_tree_delete+0x190/0x370 lib/radix-tree.c:1378
radix_tree_delete_item+0xe7/0x230 lib/radix-tree.c:1429
io_remove_personalities+0x1b/0xb0 fs/io_uring.c:7769
idr_for_each+0x113/0x220 lib/idr.c:208
io_ring_ctx_wait_and_kill+0x374/0x600 fs/io_uring.c:7810
io_uring_release+0x3e/0x50 fs/io_uring.c:7829
__fput+0x285/0x920 fs/file_table.c:281
task_work_run+0xdd/0x190 kernel/task_work.c:135
exit_task_work include/linux/task_work.h:25 [inline]
do_exit+0xb7d/0x29f0 kernel/exit.c:806
do_group_exit+0x125/0x310 kernel/exit.c:903
get_signal+0x40b/0x1ee0 kernel/signal.c:2743
arch_do_signal+0x82/0x2520 arch/x86/kernel/signal.c:811
exit_to_user_mode_loop kernel/entry/common.c:135 [inline]
exit_to_user_mode_prepare+0x172/0x1d0 kernel/entry/common.c:166
syscall_exit_to_user_mode+0x59/0x2b0 kernel/entry/common.c:241
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:2894 [inline]
call_rcu+0x14f/0x7e0 kernel/rcu/tree.c:2968
radix_tree_node_free lib/radix-tree.c:309 [inline]
delete_node+0x587/0x8a0 lib/radix-tree.c:572
__radix_tree_delete+0x190/0x370 lib/radix-tree.c:1378
radix_tree_delete_item+0xe7/0x230 lib/radix-tree.c:1429
io_remove_personalities+0x1b/0xb0 fs/io_uring.c:7769
idr_for_each+0x113/0x220 lib/idr.c:208
io_ring_ctx_wait_and_kill+0x374/0x600 fs/io_uring.c:7810
io_uring_release+0x3e/0x50 fs/io_uring.c:7829
__fput+0x285/0x920 fs/file_table.c:281
task_work_run+0xdd/0x190 kernel/task_work.c:135
exit_task_work include/linux/task_work.h:25 [inline]
do_exit+0xb7d/0x29f0 kernel/exit.c:806
do_group_exit+0x125/0x310 kernel/exit.c:903
get_signal+0x40b/0x1ee0 kernel/signal.c:2743
arch_do_signal+0x82/0x2520 arch/x86/kernel/signal.c:811
exit_to_user_mode_loop kernel/entry/common.c:135 [inline]
exit_to_user_mode_prepare+0x172/0x1d0 kernel/entry/common.c:166
syscall_exit_to_user_mode+0x59/0x2b0 kernel/entry/common.c:241
entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff888082058c40
which belongs to the cache radix_tree_node of size 576
The buggy address is located 56 bytes inside of
576-byte region [ffff888082058c40, ffff888082058e80)
The buggy address belongs to the page:
page:0000000023bf3329 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888082058ffb pfn:0x82058
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002080ac8 ffffea0002080cc8 ffff8880aa06f000
raw: ffff888082058ffb ffff888082058140 0000000100000005 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888082058b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888082058b80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff888082058c00: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
^
ffff888082058c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888082058d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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[Jens Axboe]

On 8/13/20 11:28 AM, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: fb893de3 Merge tag 'tag-chrome-platform-for-v5.9' of git:/..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=167ed216900000
> kernel config: https://syzkaller.appspot.com/x/.config?x=f1fedc63022bf07e
> dashboard link: https://syzkaller.appspot.com/bug?extid=25d82ed5cc4b474f1df8
> compiler: gcc (GCC) 10.1.0-syz 20200507
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=107bc222900000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17a09d06900000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+25d82e...@syzkaller.appspotmail.com
>
> ==================================================================
> BUG: KASAN: use-after-free in radix_tree_next_slot include/linux/radix-tree.h:421 [inline]
> BUG: KASAN: use-after-free in idr_for_each+0x206/0x220 lib/idr.c:202
> Read of size 8 at addr ffff888082058c78 by task syz-executor999/3765

Should already be fixed by:

commit 6d816e088c359866f9867057e04f244c608c42fe
Author: Jens Axboe <ax...@kernel.dk>
Date: Tue Aug 11 08:04:14 2020 -0600

io_uring: hold 'ctx' reference around task_work queue + execute

which is going upstream soon.

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

--
Jens Axboe