Re: [syzbot] WARNING in io_link_timeout_fn

[Pavel Begunkov <asml.silence@gmail.com>]

On 5/14/21 1:08 AM, syzbot wrote:
> Hello,
> 
> syzbot has tested the proposed patch but the reproducer is still triggering an issue:
> KASAN: use-after-free Read in hrtimer_active

#syz test: https://github.com/isilence/linux.git syz_test8

> ==================================================================
> BUG: KASAN: use-after-free in hrtimer_active+0x1d6/0x1f0 kernel/time/hrtimer.c:1462
> Read of size 8 at addr ffff8880129a64b8 by task syz-executor.0/9928
> 
> CPU: 0 PID: 9928 Comm: syz-executor.0 Not tainted 5.12.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:79 [inline]
>  dump_stack+0x141/0x1d7 lib/dump_stack.c:120
>  print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:233
>  __kasan_report mm/kasan/report.c:419 [inline]
>  kasan_report.cold+0x7c/0xd8 mm/kasan/report.c:436
>  hrtimer_active+0x1d6/0x1f0 kernel/time/hrtimer.c:1462
>  hrtimer_try_to_cancel+0x21/0x1e0 kernel/time/hrtimer.c:1180
>  io_kill_linked_timeout fs/io_uring.c:1794 [inline]
>  io_disarm_next+0x196/0xad0 fs/io_uring.c:1827
>  __io_req_find_next+0xca/0x160 fs/io_uring.c:1852
>  io_req_find_next fs/io_uring.c:1868 [inline]
>  io_queue_next fs/io_uring.c:2070 [inline]
>  io_free_req fs/io_uring.c:2078 [inline]
>  io_put_req_deferred_cb+0x253/0x4a0 fs/io_uring.c:2180
>  __tctx_task_work fs/io_uring.c:1909 [inline]
>  tctx_task_work+0x24e/0x550 fs/io_uring.c:1923
>  task_work_run+0xdd/0x1a0 kernel/task_work.c:161
>  tracehook_notify_signal include/linux/tracehook.h:212 [inline]
>  handle_signal_work kernel/entry/common.c:145 [inline]
>  exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
>  exit_to_user_mode_prepare+0x24a/0x280 kernel/entry/common.c:208
>  __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
>  syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:301
>  do_syscall_64+0x47/0xb0 arch/x86/entry/common.c:57
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x4665f9
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f9092a97188 EFLAGS: 00000246 ORIG_RAX: 00000000000001aa
> RAX: 0000000000000100 RBX: 000000000056bf60 RCX: 00000000004665f9
> RDX: 0000000000000000 RSI: 000000000000450c RDI: 0000000000000003
> RBP: 00000000004bfce1 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60
> R13: 0000000000a9fb1f R14: 00007f9092a97300 R15: 0000000000022000
> 
> Allocated by task 9928:
>  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_kmalloc mm/kasan/common.c:506 [inline]
>  ____kasan_kmalloc mm/kasan/common.c:465 [inline]
>  __kasan_kmalloc+0x99/0xc0 mm/kasan/common.c:515
>  kmalloc include/linux/slab.h:561 [inline]
>  io_alloc_async_data fs/io_uring.c:3116 [inline]
>  io_timeout_prep+0x3d9/0x500 fs/io_uring.c:5637
>  io_req_prep fs/io_uring.c:5908 [inline]
>  io_submit_sqe fs/io_uring.c:6576 [inline]
>  io_submit_sqes+0x4e4c/0x6c50 fs/io_uring.c:6734
>  __do_sys_io_uring_enter+0xeaf/0x1d50 fs/io_uring.c:9319
>  do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> Freed by task 4826:
>  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:1563 [inline]
>  slab_free_freelist_hook+0x92/0x210 mm/slub.c:1601
>  slab_free mm/slub.c:3162 [inline]
>  kfree+0xe5/0x7f0 mm/slub.c:4216
>  io_dismantle_req+0x116/0x250 fs/io_uring.c:1743
>  io_req_complete_post+0x1d7/0x890 fs/io_uring.c:1600
>  io_link_timeout_fn+0x5f7/0xb10 fs/io_uring.c:6369
>  __run_hrtimer kernel/time/hrtimer.c:1537 [inline]
>  __hrtimer_run_queues+0x609/0xe40 kernel/time/hrtimer.c:1601
>  hrtimer_interrupt+0x330/0xa00 kernel/time/hrtimer.c:1663
>  local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1089 [inline]
>  __sysvec_apic_timer_interrupt+0x146/0x540 arch/x86/kernel/apic/apic.c:1106
>  sysvec_apic_timer_interrupt+0x8e/0xc0 arch/x86/kernel/apic/apic.c:1100
>  asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:632
> 
> The buggy address belongs to the object at ffff8880129a6480
>  which belongs to the cache kmalloc-96 of size 96
> The buggy address is located 56 bytes inside of
>  96-byte region [ffff8880129a6480, ffff8880129a64e0)
> The buggy address belongs to the page:
> page:ffffea00004a6980 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x129a6
> flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
> raw: 00fff00000000200 dead000000000100 dead000000000122 ffff888010841780
> raw: 0000000000000000 0000000000200020 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> page_owner tracks the page as allocated
> page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 9928, ts 107924339577
>  set_page_owner include/linux/page_owner.h:31 [inline]
>  post_alloc_hook+0x161/0x1c0 mm/page_alloc.c:2302
>  prep_new_page mm/page_alloc.c:2311 [inline]
>  get_page_from_freelist+0x1c6f/0x3fb0 mm/page_alloc.c:3951
>  __alloc_pages_nodemask+0x2d6/0x730 mm/page_alloc.c:5001
>  alloc_pages_current+0x18c/0x2a0 mm/mempolicy.c:2277
>  alloc_pages include/linux/gfp.h:561 [inline]
>  alloc_slab_page mm/slub.c:1639 [inline]
>  allocate_slab+0x2c5/0x4c0 mm/slub.c:1779
>  new_slab mm/slub.c:1842 [inline]
>  new_slab_objects mm/slub.c:2588 [inline]
>  ___slab_alloc+0x44c/0x7a0 mm/slub.c:2751
>  __slab_alloc.constprop.0+0xa7/0xf0 mm/slub.c:2791
>  slab_alloc_node mm/slub.c:2872 [inline]
>  slab_alloc mm/slub.c:2916 [inline]
>  __kmalloc+0x2e5/0x300 mm/slub.c:4054
>  kmalloc include/linux/slab.h:561 [inline]
>  io_alloc_async_data fs/io_uring.c:3116 [inline]
>  io_timeout_prep+0x3d9/0x500 fs/io_uring.c:5637
>  io_req_prep fs/io_uring.c:5908 [inline]
>  io_submit_sqe fs/io_uring.c:6576 [inline]
>  io_submit_sqes+0x4e4c/0x6c50 fs/io_uring.c:6734
>  __do_sys_io_uring_enter+0xeaf/0x1d50 fs/io_uring.c:9319
>  do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> page last free stack trace:
>  reset_page_owner include/linux/page_owner.h:24 [inline]
>  free_pages_prepare mm/page_alloc.c:1271 [inline]
>  free_pcp_prepare+0x2cb/0x410 mm/page_alloc.c:1310
>  free_unref_page_prepare mm/page_alloc.c:3205 [inline]
>  free_unref_page+0x12/0x1d0 mm/page_alloc.c:3253
>  qlink_free mm/kasan/quarantine.c:146 [inline]
>  qlist_free_all+0x5a/0xc0 mm/kasan/quarantine.c:165
>  kasan_quarantine_reduce+0x180/0x200 mm/kasan/quarantine.c:272
>  __kasan_slab_alloc+0x7f/0x90 mm/kasan/common.c:437
>  kasan_slab_alloc include/linux/kasan.h:223 [inline]
>  slab_post_alloc_hook mm/slab.h:516 [inline]
>  slab_alloc_node mm/slub.c:2908 [inline]
>  slab_alloc mm/slub.c:2916 [inline]
>  kmem_cache_alloc+0x153/0x370 mm/slub.c:2921
>  getname_flags.part.0+0x50/0x4f0 fs/namei.c:138
>  getname_flags include/linux/audit.h:319 [inline]
>  getname+0x8e/0xd0 fs/namei.c:209
>  do_sys_openat2+0xf5/0x420 fs/open.c:1181
>  do_sys_open fs/open.c:1203 [inline]
>  __do_sys_open fs/open.c:1211 [inline]
>  __se_sys_open fs/open.c:1207 [inline]
>  __x64_sys_open+0x119/0x1c0 fs/open.c:1207
>  do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> Memory state around the buggy address:
>  ffff8880129a6380: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>  ffff8880129a6400: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
>> ffff8880129a6480: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>                                         ^
>  ffff8880129a6500: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>  ffff8880129a6580: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> ==================================================================
> 
> 
> Tested on:
> 
> commit:         a519b86e io_uring: syz debug output
> git tree:       https://github.com/isilence/linux.git syz_test6
> console output: https://syzkaller.appspot.com/x/log.txt?x=14127779d00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=ae2e6c63d6410fd3
> dashboard link: https://syzkaller.appspot.com/bug?extid=5a864149dd970b546223
> compiler:       
> 

-- 
Pavel Begunkov