Re: [syzbot] KASAN: use-after-free Read in __io_req_task_work_add

[syzbot]

> On 1/12/23 10:26, syzbot wrote:
>> Hello,
>> 
>> syzbot found the following issue on:
>> 
>> HEAD commit:    0a093b2893c7 Add linux-next specific files for 20230112
>> git tree:       linux-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=111a5a86480000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=835f3591019836d5
>> dashboard link: https://syzkaller.appspot.com/bug?extid=01db4d8aed628ede44b1
>> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>> 
>> Unfortunately, I don't have any reproducer for this issue yet.
>
> #syz test: git://git.kernel.dk/linux.git syztest

This crash does not have a reproducer. I cannot test it.

>
>> 
>> Downloadable assets:
>> disk image: https://storage.googleapis.com/syzbot-assets/8111a570d6cb/disk-0a093b28.raw.xz
>> vmlinux: https://storage.googleapis.com/syzbot-assets/ecc135b7fc9a/vmlinux-0a093b28.xz
>> kernel image: https://storage.googleapis.com/syzbot-assets/ca8d73b446ea/bzImage-0a093b28.xz
>> 
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+01db4d8aed628ede44b1@xxxxxxxxxxxxxxxxxxxxxxxxx
>> 
>> ==================================================================
>> BUG: KASAN: use-after-free in __io_req_task_work_add+0x6b4/0x760 io_uring/io_uring.c:1287
>> Read of size 8 at addr ffff888027236018 by task syz-executor.3/11047
>> 
>> CPU: 0 PID: 11047 Comm: syz-executor.3 Not tainted 6.2.0-rc3-next-20230112-syzkaller #0
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
>> Call Trace:
>>   <TASK>
>>   __dump_stack lib/dump_stack.c:88 [inline]
>>   dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106
>>   print_address_description mm/kasan/report.c:306 [inline]
>>   print_report+0x15e/0x45d mm/kasan/report.c:417
>>   kasan_report+0xc0/0xf0 mm/kasan/report.c:517
>>   __io_req_task_work_add+0x6b4/0x760 io_uring/io_uring.c:1287
>>   io_req_task_work_add io_uring/io_uring.h:95 [inline]
>>   __io_poll_execute io_uring/poll.c:366 [inline]
>>   io_poll_execute.constprop.0+0x15b/0x190 io_uring/poll.c:372
>>   io_poll_cancel_req io_uring/poll.c:379 [inline]
>>   io_poll_remove_all_table+0x26d/0x2bd io_uring/poll.c:741
>>   io_poll_remove_all+0x2e/0x4b io_uring/poll.c:759
>>   io_ring_ctx_wait_and_kill+0x1a0/0x340 io_uring/io_uring.c:3017
>>   io_uring_release+0x46/0x4a io_uring/io_uring.c:3042
>>   __fput+0x27c/0xa90 fs/file_table.c:321
>>   task_work_run+0x16f/0x270 kernel/task_work.c:179
>>   exit_task_work include/linux/task_work.h:38 [inline]
>>   do_exit+0xb17/0x2a90 kernel/exit.c:867
>>   do_group_exit+0xd4/0x2a0 kernel/exit.c:1012
>>   __do_sys_exit_group kernel/exit.c:1023 [inline]
>>   __se_sys_exit_group kernel/exit.c:1021 [inline]
>>   __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1021
>>   do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>>   do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>>   entry_SYSCALL_64_after_hwframe+0x63/0xcd
>> RIP: 0033:0x7fd01608c0c9
>> Code: Unable to access opcode bytes at 0x7fd01608c09f.
>> RSP: 002b:00007ffe4aaf8e78 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
>> RAX: ffffffffffffffda RBX: 000000000000001e RCX: 00007fd01608c0c9
>> RDX: 00007fd01603df7b RSI: ffffffffffffffb8 RDI: 0000000000000000
>> RBP: 0000000000000000 R08: 0000000023b38e02 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
>> R13: 0000000000000000 R14: 0000000000000001 R15: 00007ffe4aaf8f60
>>   </TASK>
>> 
>> Allocated by task 11047:
>>   kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
>>   kasan_set_track+0x25/0x30 mm/kasan/common.c:52
>>   __kasan_slab_alloc+0x7f/0x90 mm/kasan/common.c:325
>>   kasan_slab_alloc include/linux/kasan.h:186 [inline]
>>   slab_post_alloc_hook mm/slab.h:769 [inline]
>>   slab_alloc_node mm/slub.c:3452 [inline]
>>   kmem_cache_alloc_node+0x183/0x350 mm/slub.c:3497
>>   alloc_task_struct_node kernel/fork.c:171 [inline]
>>   dup_task_struct kernel/fork.c:979 [inline]
>>   copy_process+0x3aa/0x7740 kernel/fork.c:2103
>>   kernel_clone+0xeb/0x9a0 kernel/fork.c:2687
>>   __do_sys_clone+0xba/0x100 kernel/fork.c:2828
>>   do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>>   do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>>   entry_SYSCALL_64_after_hwframe+0x63/0xcd
>> 
>> Freed by task 15:
>>   kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
>>   kasan_set_track+0x25/0x30 mm/kasan/common.c:52
>>   kasan_save_free_info+0x2e/0x40 mm/kasan/generic.c:518
>>   ____kasan_slab_free mm/kasan/common.c:236 [inline]
>>   ____kasan_slab_free+0x160/0x1c0 mm/kasan/common.c:200
>>   kasan_slab_free include/linux/kasan.h:162 [inline]
>>   slab_free_hook mm/slub.c:1781 [inline]
>>   slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1807
>>   slab_free mm/slub.c:3787 [inline]
>>   kmem_cache_free+0xec/0x4e0 mm/slub.c:3809
>>   put_task_struct include/linux/sched/task.h:119 [inline]
>>   delayed_put_task_struct+0x26e/0x3f0 kernel/exit.c:225
>>   rcu_do_batch kernel/rcu/tree.c:2113 [inline]
>>   rcu_core+0x821/0x1920 kernel/rcu/tree.c:2373
>>   __do_softirq+0x1fb/0xaf6 kernel/softirq.c:571
>> 
>> Last potentially related work creation:
>>   kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
>>   __kasan_record_aux_stack+0xbc/0xd0 mm/kasan/generic.c:488
>>   __call_rcu_common.constprop.0+0x99/0x780 kernel/rcu/tree.c:2622
>>   put_task_struct_rcu_user+0x83/0xc0 kernel/exit.c:231
>>   context_switch kernel/sched/core.c:5304 [inline]
>>   __schedule+0x25d8/0x5a70 kernel/sched/core.c:6619
>>   preempt_schedule_common+0x45/0xc0 kernel/sched/core.c:6788
>>   preempt_schedule_thunk+0x1a/0x20 arch/x86/entry/thunk_64.S:34
>>   __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:160 [inline]
>>   _raw_spin_unlock_irq+0x40/0x50 kernel/locking/spinlock.c:202
>>   spin_unlock_irq include/linux/spinlock.h:400 [inline]
>>   do_group_exit+0x1c5/0x2a0 kernel/exit.c:1009
>>   __do_sys_exit_group kernel/exit.c:1023 [inline]
>>   __se_sys_exit_group kernel/exit.c:1021 [inline]
>>   __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1021
>>   do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>>   do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>>   entry_SYSCALL_64_after_hwframe+0x63/0xcd
>> 
>> Second to last potentially related work creation:
>>   kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
>>   __kasan_record_aux_stack+0xbc/0xd0 mm/kasan/generic.c:488
>>   __call_rcu_common.constprop.0+0x99/0x780 kernel/rcu/tree.c:2622
>>   put_task_struct_rcu_user+0x83/0xc0 kernel/exit.c:231
>>   release_task+0xcc8/0x1870 kernel/exit.c:281
>>   wait_task_zombie kernel/exit.c:1198 [inline]
>>   wait_consider_task+0x306d/0x3ce0 kernel/exit.c:1425
>>   do_wait_thread kernel/exit.c:1488 [inline]
>>   do_wait+0x7cd/0xd90 kernel/exit.c:1605
>>   kernel_wait4+0x150/0x260 kernel/exit.c:1768
>>   __do_sys_wait4+0x13f/0x150 kernel/exit.c:1796
>>   do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>>   do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>>   entry_SYSCALL_64_after_hwframe+0x63/0xcd
>> 
>> The buggy address belongs to the object at ffff8880272357c0
>>   which belongs to the cache task_struct of size 7232
>> The buggy address is located 2136 bytes inside of
>>   7232-byte region [ffff8880272357c0, ffff888027237400)
>> 
>> The buggy address belongs to the physical page:
>> page:ffffea00009c8c00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x27230
>> head:ffffea00009c8c00 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
>> memcg:ffff8880219a5c01
>> ksm flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
>> raw: 00fff00000010200 ffff8880125ec500 ffffea0000ab3800 dead000000000003
>> raw: 0000000000000000 0000000000040004 00000001ffffffff ffff8880219a5c01
>> page dumped because: kasan: bad access detected
>> page_owner tracks the page as allocated
>> page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 56, tgid 56 (kworker/u4:4), ts 11164250893, free_ts 0
>>   prep_new_page mm/page_alloc.c:2549 [inline]
>>   get_page_from_freelist+0x11bb/0x2d50 mm/page_alloc.c:4324
>>   __alloc_pages+0x1cb/0x5c0 mm/page_alloc.c:5590
>>   alloc_pages+0x1aa/0x270 mm/mempolicy.c:2281
>>   alloc_slab_page mm/slub.c:1851 [inline]
>>   allocate_slab+0x25f/0x350 mm/slub.c:1998
>>   new_slab mm/slub.c:2051 [inline]
>>   ___slab_alloc+0xa91/0x1400 mm/slub.c:3193
>>   __slab_alloc.constprop.0+0x56/0xa0 mm/slub.c:3292
>>   __slab_alloc_node mm/slub.c:3345 [inline]
>>   slab_alloc_node mm/slub.c:3442 [inline]
>>   kmem_cache_alloc_node+0x136/0x350 mm/slub.c:3497
>>   alloc_task_struct_node kernel/fork.c:171 [inline]
>>   dup_task_struct kernel/fork.c:979 [inline]
>>   copy_process+0x3aa/0x7740 kernel/fork.c:2103
>>   kernel_clone+0xeb/0x9a0 kernel/fork.c:2687
>>   user_mode_thread+0xb1/0xf0 kernel/fork.c:2763
>>   call_usermodehelper_exec_work kernel/umh.c:175 [inline]
>>   call_usermodehelper_exec_work+0xd0/0x180 kernel/umh.c:161
>>   process_one_work+0x9bf/0x1750 kernel/workqueue.c:2293
>>   worker_thread+0x669/0x1090 kernel/workqueue.c:2440
>>   kthread+0x2e8/0x3a0 kernel/kthread.c:376
>>   ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
>> page_owner free stack trace missing
>> 
>> Memory state around the buggy address:
>>   ffff888027235f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>   ffff888027235f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>> ffff888027236000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>                              ^
>>   ffff888027236080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>   ffff888027236100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>> ==================================================================
>> 
>> 
>> ---
>> This report is generated by a bot. It may contain errors.
>> See https://goo.gl/tpsmEJ for more information about syzbot.
>> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.
>> 
>> syzbot will keep track of this issue. See:
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>
> -- 
> Pavel Begunkov