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Tue, 09 Mar 2021 14:29:07 -0800 (PST) Date: Tue, 09 Mar 2021 14:29:07 -0800 In-Reply-To: <5112d102-d849-c640-868f-ee820163d02e@kernel.dk> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <00000000000023b36405bd221483@google.com> Subject: Re: [syzbot] possible deadlock in io_sq_thread_finish From: syzbot To: asml.silence@gmail.com, axboe@kernel.dk, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org Hello, syzbot has tested the proposed patch but the reproducer is still triggering an issue: KASAN: use-after-free Read in io_sq_thread ================================================================== BUG: KASAN: use-after-free in __lock_acquire+0x3e6f/0x54c0 kernel/locking/lockdep.c:4770 Read of size 8 at addr ffff888034cbfc78 by task iou-sqp-10518/10523 CPU: 0 PID: 10523 Comm: iou-sqp-10518 Not tainted 5.12.0-rc2-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: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/0x740 kernel/locking/lockdep.c:5475 down_write+0x92/0x150 kernel/locking/rwsem.c:1406 io_sq_thread+0x1220/0x1b10 fs/io_uring.c:6754 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 Allocated by task 10518: 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:554 [inline] kzalloc include/linux/slab.h:684 [inline] io_get_sq_data fs/io_uring.c:7156 [inline] io_sq_offload_create fs/io_uring.c:7830 [inline] io_uring_create fs/io_uring.c:9443 [inline] io_uring_setup+0x1552/0x2860 fs/io_uring.c:9523 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xae Freed by task 396: 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+0x92/0x210 mm/slub.c:1600 slab_free mm/slub.c:3161 [inline] kfree+0xe5/0x7f0 mm/slub.c:4213 io_put_sq_data fs/io_uring.c:7098 [inline] io_sq_thread_finish+0x4b0/0x5f0 fs/io_uring.c:7116 io_ring_ctx_free fs/io_uring.c:8355 [inline] io_ring_exit_work+0x333/0xcf0 fs/io_uring.c:8525 process_one_work+0x98d/0x1600 kernel/workqueue.c:2275 worker_thread+0x64c/0x1120 kernel/workqueue.c:2421 kthread+0x3b1/0x4a0 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 The buggy address belongs to the object at ffff888034cbfc00 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 120 bytes inside of 512-byte region [ffff888034cbfc00, ffff888034cbfe00) The buggy address belongs to the page: page:000000004a1f04c4 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x34cbc head:000000004a1f04c4 order:2 compound_mapcount:0 compound_pincount:0 flags: 0xfff00000010200(slab|head) raw: 00fff00000010200 dead000000000100 dead000000000122 ffff88800fc41c80 raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888034cbfb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888034cbfb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff888034cbfc00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888034cbfc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888034cbfd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== Tested on: commit: 8bf06ba6 io_uring: remove unneeded variable 'ret' git tree: git://git.kernel.dk/linux-block io_uring-5.12 console output: https://syzkaller.appspot.com/x/log.txt?x=13fcd952d00000 kernel config: https://syzkaller.appspot.com/x/.config?x=b3c6cab008c50864 dashboard link: https://syzkaller.appspot.com/bug?extid=ac39856cb1b332dbbdda compiler: