Date:   Thu, 25 Feb 2021 09:53:00 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     syzbot <syzbot+7bf785eedca35ca05501@...kaller.appspotmail.com>,
        asml.silence@...il.com, christian@...uner.io,
        io-uring@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: KASAN: use-after-free Read in try_to_wake_up

On 2/25/21 9:47 AM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    577c2835 Add linux-next specific files for 20210224
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=1586e0dad00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e9bb3d369b3bf49
> dashboard link: https://syzkaller.appspot.com/bug?extid=7bf785eedca35ca05501
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16609646d00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1529c5a8d00000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+7bf785eedca35ca05501@...kaller.appspotmail.com
> 
> ==================================================================
> BUG: KASAN: use-after-free in __lock_acquire+0x3e6f/0x54c0 kernel/locking/lockdep.c:4770
> Read of size 8 at addr ffff888030dc08d0 by task syz-executor199/9383
> 
> CPU: 1 PID: 9383 Comm: syz-executor199 Not tainted 5.11.0-next-20210224-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:79 [inline]
>  dump_stack+0xfa/0x151 lib/dump_stack.c:120
>  print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:232
>  __kasan_report mm/kasan/report.c:399 [inline]
>  kasan_report.cold+0x7c/0xd8 mm/kasan/report.c:416
>  __lock_acquire+0x3e6f/0x54c0 kernel/locking/lockdep.c:4770
>  lock_acquire kernel/locking/lockdep.c:5510 [inline]
>  lock_acquire+0x1ab/0x730 kernel/locking/lockdep.c:5475
>  __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>  _raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:159
>  try_to_wake_up+0x98/0x14a0 kernel/sched/core.c:3347
>  io_wq_destroy+0x74/0x3d0 fs/io-wq.c:1013
>  __io_uring_files_cancel+0x195/0x230 fs/io_uring.c:8810
>  io_uring_files_cancel include/linux/io_uring.h:47 [inline]
>  do_exit+0x299/0x2a60 kernel/exit.c:780
>  do_group_exit+0x125/0x310 kernel/exit.c:922
>  __do_sys_exit_group kernel/exit.c:933 [inline]
>  __se_sys_exit_group kernel/exit.c:931 [inline]
>  __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:931
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x43e989
> Code: 00 49 c7 c0 c0 ff ff ff be e7 00 00 00 ba 3c 00 00 00 eb 12 0f 1f 44 00 00 89 d0 0f 05 48 3d 00 f0 ff ff 77 1c f4 89 f0 0f 05 <48> 3d 00 f0 ff ff 76 e7 f7 d8 64 41 89 00 eb df 0f 1f 80 00 00 00
> RSP: 002b:00007ffe3a2de828 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
> RAX: ffffffffffffffda RBX: 00000000004b02f0 RCX: 000000000043e989
> RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
> RBP: 0000000000000000 R08: ffffffffffffffc0 R09: 0000000010000000
> R10: 0000000000008011 R11: 0000000000000246 R12: 00000000004b02f0
> R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001
> 
> Allocated by task 9383:
>  kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
>  kasan_set_track mm/kasan/common.c:46 [inline]
>  set_alloc_info mm/kasan/common.c:427 [inline]
>  __kasan_slab_alloc+0x75/0x90 mm/kasan/common.c:460
>  kasan_slab_alloc include/linux/kasan.h:223 [inline]
>  slab_post_alloc_hook mm/slab.h:516 [inline]
>  slab_alloc_node mm/slub.c:2907 [inline]
>  kmem_cache_alloc_node+0x16d/0x3c0 mm/slub.c:2943
>  alloc_task_struct_node kernel/fork.c:170 [inline]
>  dup_task_struct kernel/fork.c:860 [inline]
>  copy_process+0x613/0x6fd0 kernel/fork.c:1940
>  kernel_clone+0xe7/0xab0 kernel/fork.c:2462
>  io_wq_fork_thread+0xa7/0xe0 fs/io-wq.c:601
>  io_wq_create+0x81c/0xab0 fs/io-wq.c:985
>  io_init_wq_offload fs/io_uring.c:7779 [inline]
>  io_uring_alloc_task_context+0x185/0x510 fs/io_uring.c:7798
>  io_uring_add_task_file+0x261/0x350 fs/io_uring.c:8737
>  io_uring_install_fd fs/io_uring.c:9336 [inline]
>  io_uring_create fs/io_uring.c:9487 [inline]
>  io_uring_setup+0x14c7/0x2c20 fs/io_uring.c:9526
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> Freed by task 12:
>  kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
>  kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
>  kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:357
>  ____kasan_slab_free mm/kasan/common.c:360 [inline]
>  ____kasan_slab_free mm/kasan/common.c:325 [inline]
>  __kasan_slab_free+0xf5/0x130 mm/kasan/common.c:367
>  kasan_slab_free include/linux/kasan.h:199 [inline]
>  slab_free_hook mm/slub.c:1562 [inline]
>  slab_free_freelist_hook+0x72/0x1b0 mm/slub.c:1600
>  slab_free mm/slub.c:3161 [inline]
>  kmem_cache_free+0x8b/0x730 mm/slub.c:3177
>  __put_task_struct+0x267/0x3f0 kernel/fork.c:742
>  put_task_struct include/linux/sched/task.h:111 [inline]
>  delayed_put_task_struct+0x1f6/0x340 kernel/exit.c:173
>  rcu_do_batch kernel/rcu/tree.c:2559 [inline]
>  rcu_core+0x722/0x1280 kernel/rcu/tree.c:2794
>  __do_softirq+0x29b/0x9f6 kernel/softirq.c:345
> 
> Last potentially related work creation:
>  kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
>  kasan_record_aux_stack+0xe5/0x110 mm/kasan/generic.c:345
>  __call_rcu kernel/rcu/tree.c:3039 [inline]
>  call_rcu+0xb1/0x700 kernel/rcu/tree.c:3114
>  put_task_struct_rcu_user+0x7f/0xb0 kernel/exit.c:179
>  context_switch kernel/sched/core.c:4327 [inline]
>  __schedule+0x914/0x21a0 kernel/sched/core.c:5075
>  preempt_schedule_common+0x45/0xc0 kernel/sched/core.c:5235
>  preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:35
>  __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
>  _raw_spin_unlock_irqrestore+0x46/0x50 kernel/locking/spinlock.c:191
>  io_wq_manager+0x13c/0x5b0 fs/io-wq.c:715
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
> 
> The buggy address belongs to the object at ffff888030dc0000
>  which belongs to the cache task_struct of size 6912
> The buggy address is located 2256 bytes inside of
>  6912-byte region [ffff888030dc0000, ffff888030dc1b00)
> The buggy address belongs to the page:
> page:00000000deb921bd refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x30dc0
> head:00000000deb921bd order:3 compound_mapcount:0 compound_pincount:0
> flags: 0xfff00000010200(slab|head)
> raw: 00fff00000010200 dead000000000100 dead000000000122 ffff888140004000
> raw: 0000000000000000 0000000080040004 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>  ffff888030dc0780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff888030dc0800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>> ffff888030dc0880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                                  ^
>  ffff888030dc0900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff888030dc0980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================

Same that trinity reported, that one already got fixed and merged
into the parent.

#syz invalid

-- 
Jens Axboe

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