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Date:   Thu, 12 Jan 2023 02:38:50 -0800
In-Reply-To: <3f4c1d69-cca2-ee6a-55e0-95028cf739da@gmail.com>
Message-ID: <000000000000fb82de05f20eb8e8@google.com>
Subject: Re: [syzbot] KASAN: use-after-free Read in io_fallback_req_func
From:   syzbot <syzbot+bc022c162e3b001bf607@syzkaller.appspotmail.com>
To:     asml.silence@gmail.com
Cc:     asml.silence@gmail.com, axboe@kernel.dk, io-uring@vger.kernel.org,
        linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com
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> On 1/12/23 10:09, 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=103269ce480000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=835f3591019836d5
>> dashboard link: https://syzkaller.appspot.com/bug?extid=bc022c162e3b001bf607
>> 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+bc022c162e3b001bf607@syzkaller.appspotmail.com
>> 
>> ==================================================================
>> BUG: KASAN: use-after-free in io_fallback_req_func+0xc7/0x204 io_uring/io_uring.c:251
>> Read of size 8 at addr ffff888070ac2e48 by task kworker/0:0/7
>> 
>> CPU: 0 PID: 7 Comm: kworker/0:0 Not tainted 6.2.0-rc3-next-20230112-syzkaller #0
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
>> Workqueue: events io_fallback_req_func
>> 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_fallback_req_func+0xc7/0x204 io_uring/io_uring.c:251
>>   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
>>   </TASK>
>> 
>> Allocated by task 7766:
>>   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]
>>   kmem_cache_alloc_bulk+0x3aa/0x730 mm/slub.c:4033
>>   __io_alloc_req_refill+0xcc/0x40b io_uring/io_uring.c:1062
>>   io_alloc_req_refill io_uring/io_uring.h:348 [inline]
>>   io_submit_sqes.cold+0x7c/0xc2 io_uring/io_uring.c:2407
>>   __do_sys_io_uring_enter+0x9e4/0x2c10 io_uring/io_uring.c:3429
>>   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 5179:
>>   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
>>   io_req_caches_free+0x1a9/0x1e6 io_uring/io_uring.c:2737
>>   io_ring_exit_work+0x2e7/0xc80 io_uring/io_uring.c:2967
>>   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
>> 
>> The buggy address belongs to the object at ffff888070ac2dc0
>>   which belongs to the cache io_kiocb of size 216
>> The buggy address is located 136 bytes inside of
>>   216-byte region [ffff888070ac2dc0, ffff888070ac2e98)
>> 
>> The buggy address belongs to the physical page:
>> page:ffffea0001c2b080 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x70ac2
>> memcg:ffff88802a81d181
>> flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
>> raw: 00fff00000000200 ffff8881461d1780 dead000000000122 0000000000000000
>> raw: 0000000000000000 00000000800c000c 00000001ffffffff ffff88802a81d181
>> page dumped because: kasan: bad access detected
>> page_owner tracks the page as allocated
>> page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 5547, tgid 5545 (syz-executor.4), ts 182131630120, free_ts 181898498774
>>   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
>>   __kmem_cache_alloc_bulk mm/slub.c:3951 [inline]
>>   kmem_cache_alloc_bulk+0x23d/0x730 mm/slub.c:4026
>>   __io_alloc_req_refill+0xcc/0x40b io_uring/io_uring.c:1062
>>   io_alloc_req_refill io_uring/io_uring.h:348 [inline]
>>   io_submit_sqes.cold+0x7c/0xc2 io_uring/io_uring.c:2407
>>   __do_sys_io_uring_enter+0x9e4/0x2c10 io_uring/io_uring.c:3429
>>   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
>> page last free stack trace:
>>   reset_page_owner include/linux/page_owner.h:24 [inline]
>>   free_pages_prepare mm/page_alloc.c:1451 [inline]
>>   free_pcp_prepare+0x4d0/0x910 mm/page_alloc.c:1501
>>   free_unref_page_prepare mm/page_alloc.c:3387 [inline]
>>   free_unref_page+0x1d/0x490 mm/page_alloc.c:3482
>>   qlink_free mm/kasan/quarantine.c:168 [inline]
>>   qlist_free_all+0x6a/0x170 mm/kasan/quarantine.c:187
>>   kasan_quarantine_reduce+0x192/0x220 mm/kasan/quarantine.c:294
>>   __kasan_slab_alloc+0x63/0x90 mm/kasan/common.c:302
>>   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]
>>   slab_alloc mm/slub.c:3460 [inline]
>>   __kmem_cache_alloc_lru mm/slub.c:3467 [inline]
>>   kmem_cache_alloc+0x175/0x320 mm/slub.c:3476
>>   kmem_cache_zalloc include/linux/slab.h:710 [inline]
>>   taskstats_tgid_alloc kernel/taskstats.c:583 [inline]
>>   taskstats_exit+0x5f3/0xb80 kernel/taskstats.c:622
>>   do_exit+0x822/0x2a90 kernel/exit.c:852
>>   do_group_exit+0xd4/0x2a0 kernel/exit.c:1012
>>   get_signal+0x225f/0x24f0 kernel/signal.c:2859
>>   arch_do_signal_or_restart+0x79/0x5c0 arch/x86/kernel/signal.c:306
>>   exit_to_user_mode_loop kernel/entry/common.c:168 [inline]
>>   exit_to_user_mode_prepare+0x11f/0x240 kernel/entry/common.c:204
>>   __syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
>>   syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:297
>>   do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86
>>   entry_SYSCALL_64_after_hwframe+0x63/0xcd
>> 
>> Memory state around the buggy address:
>>   ffff888070ac2d00: fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc fc
>>   ffff888070ac2d80: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
>>> ffff888070ac2e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>                                                ^
>>   ffff888070ac2e80: fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc fc
>>   ffff888070ac2f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>> ==================================================================
>> 
>> 
>> ---
>> 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@googlegroups.com.
>> 
>> syzbot will keep track of this issue. See:
>> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> -- 
> Pavel Begunkov