[syzbot] [mm?] possible deadlock in dup_mmap

[syzbot] [mm?] possible deadlock in dup_mmap

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    7e1392a42ea2 Merge tag 'net-7.4-rc3' of git://git.kernel.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10de62c3580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e3d788a0111c0780
dashboard link: https://syzkaller.appspot.com/bug?extid=1cd3a506d57e74040004
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cab3108790d1/disk-7e1392a4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d2cfcac3b02d/vmlinux-7e1392a4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0b6b5a126605/bzImage-7e1392a4.xz

AI-generated root cause summary:
The circular locking dependency is rooted in drivers/block/nbd.c, where the
Network Block Device driver handles block I/O under direct memory reclaim
(fs_reclaim) using a network socket provided by userspace. In
nbd_reclassify_socket(), NBD silently fails to reclassify the socket's lockdep
class when sock_allow_reclassification() returns false (e.g., if the socket is
already in use by userspace), leaving it in the generic sk_lock-AF_INET6 class.
Furthermore, because userspace retains the socket descriptor, concurrent user
operations like sendmsg() acquire lock_sock before faulting on user buffers
(which acquires mm->mmap_lock), while NBD I/O and shutdown paths (e.g.,
nbd_mark_nsock_dead()) acquire lock_sock via kernel_sock_shutdown() under
nsock->tx_lock in the fs_reclaim path. Because MM operations (such as
fork/dup_mmap) take mm->mmap_lock and hugetlbfs_i_mmap_rwsem_key prior to
GFP_KERNEL allocations (fs_reclaim), this establishes an inverted cycle:
mm->mmap_lock -> hugetlbfs_i_mmap_rwsem_key -> fs_reclaim -> nsock->tx_lock ->
sk_lock -> mm->mmap_lock.

full analysis:  https://syzkaller.appspot.com/x/ai_root_cause?x=1cd3a506d57e74040004

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1cd3a506d57e74040004@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.9.7569/29103 is trying to acquire lock:
ffff888052efb930 (&hugetlbfs_i_mmap_rwsem_key){+.+.}-{4:4}, at: i_mmap_lock_write include/linux/fs.h:508 [inline]
ffff888052efb930 (&hugetlbfs_i_mmap_rwsem_key){+.+.}-{4:4}, at: dup_mmap+0xb09/0x2180 mm/mmap.c:1802

but task is already holding lock:
ffff88807fe0e540 (&mm->mmap_lock/1){+.+.}-{4:4}, at: mmap_write_lock_nested include/linux/mmap_lock.h:556 [inline]
ffff88807fe0e540 (&mm->mmap_lock/1){+.+.}-{4:4}, at: dup_mmap+0x16e/0x2180 mm/mmap.c:1722

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #9 (&mm->mmap_lock/1){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       down_write_nested+0x8f/0x1f0 kernel/locking/rwsem.c:1757
       mmap_write_lock_nested include/linux/mmap_lock.h:556 [inline]
       dup_mmap+0x16e/0x2180 mm/mmap.c:1722
       dup_mm kernel/fork.c:1549 [inline]
       copy_mm kernel/fork.c:1602 [inline]
       copy_process+0x7c5c/0x88e0 kernel/fork.c:2328
       kernel_clone+0x176/0x9d0 kernel/fork.c:2798
       __do_sys_clone+0xd9/0x120 kernel/fork.c:2940
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x123/0x7b0 arch/x86/entry/syscall_64.c:89
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #8 (&mm->mmap_lock){++++}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       __might_fault+0xde/0x140 mm/memory.c:7575
       _inline_copy_from_user include/linux/uaccess.h:169 [inline]
       _copy_from_user+0x29/0xd0 lib/usercopy.c:18
       copy_from_user include/linux/uaccess.h:222 [inline]
       csum_and_copy_from_user include/net/checksum.h:31 [inline]
       copy_from_user_iter_csum net/core/skbuff.c:7677 [inline]
       iterate_ubuf include/linux/iov_iter.h:30 [inline]
       iterate_and_advance2 include/linux/iov_iter.h:302 [inline]
       csum_and_copy_from_iter_full+0x21a/0x1fe0 net/core/skbuff.c:7689
       ip_generic_getfrag+0x172/0x270 net/ipv4/ip_output.c:949
       raw6_getfrag+0x22c/0x290 net/ipv6/raw.c:743
       __ip6_append_data+0x37f0/0x4b30 net/ipv6/ip6_output.c:1739
       ip6_append_data net/ipv6/ip6_output.c:1894 [inline]
       ip6_append_data+0x10b/0x410 net/ipv6/ip6_output.c:1863
       rawv6_sendmsg+0x169c/0x4630 net/ipv6/raw.c:917
       inet_sendmsg+0x11c/0x140 net/ipv4/af_inet.c:866
       sock_sendmsg_nosec net/socket.c:800 [inline]
       __sock_sendmsg net/socket.c:818 [inline]
       ____sys_sendmsg+0x9a0/0xb90 net/socket.c:2713
       ___sys_sendmsg+0x208/0x270 net/socket.c:2770
       __sys_sendmsg+0x160/0x210 net/socket.c:2802
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x123/0x7b0 arch/x86/entry/syscall_64.c:89
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #7 (sk_lock-AF_INET6){+.+.}-{0:0}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       lock_sock_nested+0x41/0xf0 net/core/sock.c:3906
       lock_sock include/net/sock.h:1717 [inline]
       inet_shutdown+0x67/0x410 net/ipv4/af_inet.c:913
       nbd_mark_nsock_dead+0xae/0x5c0 drivers/block/nbd.c:319
       sock_shutdown+0x16b/0x200 drivers/block/nbd.c:420
       nbd_clear_sock drivers/block/nbd.c:1463 [inline]
       nbd_config_put+0x3d5/0x9b0 drivers/block/nbd.c:1492
       nbd_genl_connect+0xd72/0x1770 drivers/block/nbd.c:2319
       genl_family_rcv_msg_doit+0x214/0x300 net/netlink/genetlink.c:1114
       genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
       genl_rcv_msg+0x560/0x800 net/netlink/genetlink.c:1209
       netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2585
       genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
       netlink_unicast_kernel net/netlink/af_netlink.c:1336 [inline]
       netlink_unicast+0x668/0x950 net/netlink/af_netlink.c:1362
       netlink_sendmsg+0x9ac/0x10c0 net/netlink/af_netlink.c:1921
       sock_sendmsg_nosec net/socket.c:800 [inline]
       __sock_sendmsg net/socket.c:818 [inline]
       ____sys_sendmsg+0xa13/0xb90 net/socket.c:2713
       ___sys_sendmsg+0x208/0x270 net/socket.c:2770
       __sys_sendmsg+0x160/0x210 net/socket.c:2802
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x123/0x7b0 arch/x86/entry/syscall_64.c:89
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #6 (&nsock->tx_lock){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19f/0x1c10 kernel/locking/mutex.c:821
       nbd_handle_cmd drivers/block/nbd.c:1143 [inline]
       nbd_queue_rq+0x42d/0xfa0 drivers/block/nbd.c:1207
       blk_mq_dispatch_rq_list+0x428/0x1e60 block/blk-mq.c:2141
       __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
       blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
       __blk_mq_sched_dispatch_requests+0xcea/0x1620 block/blk-mq-sched.c:307
       blk_mq_sched_dispatch_requests+0xd7/0x1c0 block/blk-mq-sched.c:329
       blk_mq_run_work_fn+0x130/0x380 block/blk-mq.c:2555
       process_one_work+0xac7/0x1b10 kernel/workqueue.c:3495
       process_scheduled_works kernel/workqueue.c:3578 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3659
       kthread+0x373/0x450 kernel/kthread.c:436
       ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #5 (&cmd->lock){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19f/0x1c10 kernel/locking/mutex.c:821
       nbd_queue_rq+0xba/0xfa0 drivers/block/nbd.c:1199
       blk_mq_dispatch_rq_list+0x428/0x1e60 block/blk-mq.c:2141
       __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
       blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
       __blk_mq_sched_dispatch_requests+0xcea/0x1620 block/blk-mq-sched.c:307
       blk_mq_sched_dispatch_requests+0xd7/0x1c0 block/blk-mq-sched.c:329
       blk_mq_run_work_fn+0x130/0x380 block/blk-mq.c:2555
       process_one_work+0xac7/0x1b10 kernel/workqueue.c:3495
       process_scheduled_works kernel/workqueue.c:3578 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3659
       kthread+0x373/0x450 kernel/kthread.c:436
       ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #4 (set->srcu){.+.+}-{0:0}:
       lock_sync kernel/locking/lockdep.c:5991 [inline]
       lock_sync+0xb5/0x120 kernel/locking/lockdep.c:5979
       srcu_lock_sync include/linux/srcu.h:261 [inline]
       __synchronize_srcu+0xa2/0x310 kernel/rcu/srcutree.c:1662
       blk_mq_wait_quiesce_done block/blk-mq.c:284 [inline]
       blk_mq_wait_quiesce_done block/blk-mq.c:281 [inline]
       blk_mq_quiesce_queue block/blk-mq.c:304 [inline]
       blk_mq_quiesce_queue+0x149/0x1c0 block/blk-mq.c:299
       elevator_switch+0x17b/0x7e0 block/elevator.c:576
       elevator_change+0x352/0x530 block/elevator.c:681
       elevator_set_default+0x29e/0x360 block/elevator.c:754
       blk_register_queue+0x49e/0x640 block/blk-sysfs.c:992
       __add_disk+0x7dd/0xf10 block/genhd.c:531
       add_disk_fwnode+0x118/0x480 block/genhd.c:600
       add_disk include/linux/blkdev.h:799 [inline]
       nbd_dev_add+0x779/0xb10 drivers/block/nbd.c:2026
       nbd_init+0x2c5/0x2e0 drivers/block/nbd.c:2743
       do_one_initcall+0x11c/0x6f0 init/main.c:1419
       do_initcall_level init/main.c:1481 [inline]
       do_initcalls init/main.c:1497 [inline]
       do_basic_setup init/main.c:1517 [inline]
       kernel_init_freeable+0x6ea/0x7b0 init/main.c:1732
       kernel_init+0x21/0x1e0 init/main.c:1622
       ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #3 (&q->elevator_lock){+.+.}-{4:4}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19f/0x1c10 kernel/locking/mutex.c:821
       elevator_change+0x1bc/0x530 block/elevator.c:679
       elevator_set_none+0x92/0xf0 block/elevator.c:769
       blk_mq_elv_switch_none block/blk-mq.c:5168 [inline]
       __blk_mq_update_nr_hw_queues block/blk-mq.c:5213 [inline]
       blk_mq_update_nr_hw_queues+0x4e1/0x1690 block/blk-mq.c:5281
       nbd_start_device+0x1a6/0xbd0 drivers/block/nbd.c:1530
       nbd_genl_connect+0xfc2/0x1770 drivers/block/nbd.c:2310
       genl_family_rcv_msg_doit+0x214/0x300 net/netlink/genetlink.c:1114
       genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
       genl_rcv_msg+0x560/0x800 net/netlink/genetlink.c:1209
       netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2585
       genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
       netlink_unicast_kernel net/netlink/af_netlink.c:1336 [inline]
       netlink_unicast+0x668/0x950 net/netlink/af_netlink.c:1362
       netlink_sendmsg+0x9ac/0x10c0 net/netlink/af_netlink.c:1921
       sock_sendmsg_nosec net/socket.c:800 [inline]
       __sock_sendmsg net/socket.c:818 [inline]
       ____sys_sendmsg+0xa13/0xb90 net/socket.c:2713
       ___sys_sendmsg+0x208/0x270 net/socket.c:2770
       __sys_sendmsg+0x160/0x210 net/socket.c:2802
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x123/0x7b0 arch/x86/entry/syscall_64.c:89
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&q->q_usage_counter(io)#49){++++}-{0:0}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       blk_alloc_queue+0x610/0x790 block/blk-core.c:505
       blk_mq_alloc_queue+0x174/0x290 block/blk-mq.c:4468
       __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4515
       nbd_dev_add+0x491/0xb10 drivers/block/nbd.c:1996
       nbd_init+0x2c5/0x2e0 drivers/block/nbd.c:2743
       do_one_initcall+0x11c/0x6f0 init/main.c:1419
       do_initcall_level init/main.c:1481 [inline]
       do_initcalls init/main.c:1497 [inline]
       do_basic_setup init/main.c:1517 [inline]
       kernel_init_freeable+0x6ea/0x7b0 init/main.c:1732
       kernel_init+0x21/0x1e0 init/main.c:1622
       ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (fs_reclaim){+.+.}-{0:0}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       __fs_reclaim_acquire mm/page_alloc.c:4375 [inline]
       fs_reclaim_acquire+0xc4/0x100 mm/page_alloc.c:4389
       might_alloc include/linux/sched/mm.h:316 [inline]
       slab_pre_alloc_hook mm/slub.c:4673 [inline]
       slab_alloc_node mm/slub.c:5011 [inline]
       __kmalloc_cache_noprof+0x63/0x6d0 mm/slub.c:5676
       _kmalloc_noprof include/linux/slab.h:991 [inline]
       allocate_file_region_entries+0x1a0/0x630 mm/hugetlb.c:711
       region_chg+0x85/0x140 mm/hugetlb.c:831
       __vma_reservation_common+0x34b/0x6f0 mm/hugetlb.c:2495
       vma_needs_reservation mm/hugetlb.c:2562 [inline]
       hugetlb_unmap_range+0x10be/0x1710 mm/hugetlb.c:5415
       __unmap_hugepage_range+0x186/0x2f0 mm/hugetlb.c:5445
       __zap_vma_range+0x3870/0x46c0 mm/memory.c:2195
       unmap_vmas+0x294/0x5f0 mm/memory.c:2275
       exit_mmap+0x1ef/0xa40 mm/mmap.c:1315
       __mmput+0x12a/0x410 kernel/fork.c:1192
       mmput+0x62/0x70 kernel/fork.c:1215
       exit_mm kernel/exit.c:586 [inline]
       do_exit+0x80c/0x2a00 kernel/exit.c:967
       do_group_exit+0xd5/0x2a0 kernel/exit.c:1123
       get_signal+0x1f58/0x22e0 kernel/signal.c:3113
       arch_do_signal_or_restart+0x91/0x7e0 arch/x86/kernel/signal.c:337
       __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
       exit_to_user_mode_loop+0x139/0x700 kernel/entry/common.c:101
       __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
       syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
       syscall_exit_to_user_mode include/linux/entry-common.h:343 [inline]
       do_syscall_64+0x661/0x7b0 arch/x86/entry/syscall_64.c:107
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&hugetlbfs_i_mmap_rwsem_key){+.+.}-{4:4}:
       check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209
       check_prevs_add kernel/locking/lockdep.c:3328 [inline]
       validate_chain kernel/locking/lockdep.c:3952 [inline]
       __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       down_write+0x86/0x1f0 kernel/locking/rwsem.c:1631
       i_mmap_lock_write include/linux/fs.h:508 [inline]
       dup_mmap+0xb09/0x2180 mm/mmap.c:1802
       dup_mm kernel/fork.c:1549 [inline]
       copy_mm kernel/fork.c:1602 [inline]
       copy_process+0x7c5c/0x88e0 kernel/fork.c:2328
       kernel_clone+0x176/0x9d0 kernel/fork.c:2798
       __do_sys_clone+0xd9/0x120 kernel/fork.c:2940
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x123/0x7b0 arch/x86/entry/syscall_64.c:89
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &hugetlbfs_i_mmap_rwsem_key --> &mm->mmap_lock --> &mm->mmap_lock/1

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&mm->mmap_lock/1);
                               lock(&mm->mmap_lock);
                               lock(&mm->mmap_lock/1);
  lock(&hugetlbfs_i_mmap_rwsem_key);

 *** DEADLOCK ***

locks held by syz.9.7569/29103: 3, on CPU#1:
 #0: ffffffff9014abf0 (dup_mmap_sem){++++}-{0:0}, at: dup_mm kernel/fork.c:1536 [inline]
 #0: ffffffff9014abf0 (dup_mmap_sem){++++}-{0:0}, at: copy_mm kernel/fork.c:1602 [inline]
 #0: ffffffff9014abf0 (dup_mmap_sem){++++}-{0:0}, at: copy_process+0x7b73/0x88e0 kernel/fork.c:2328
 #1: ffff88807fe0ccc0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock_killable include/linux/mmap_lock.h:566 [inline]
 #1: ffff88807fe0ccc0 (&mm->mmap_lock){++++}-{4:4}, at: dup_mm kernel/fork.c:1537 [inline]
 #1: ffff88807fe0ccc0 (&mm->mmap_lock){++++}-{4:4}, at: copy_mm kernel/fork.c:1602 [inline]
 #1: ffff88807fe0ccc0 (&mm->mmap_lock){++++}-{4:4}, at: copy_process+0x7b99/0x88e0 kernel/fork.c:2328
 #2: ffff88807fe0e540 (&mm->mmap_lock/1){+.+.}-{4:4}, at: mmap_write_lock_nested include/linux/mmap_lock.h:556 [inline]
 #2: ffff88807fe0e540 (&mm->mmap_lock/1){+.+.}-{4:4}, at: dup_mmap+0x16e/0x2180 mm/mmap.c:1722

stack backtrace:
CPU: 1 UID: 0 PID: 29103 Comm: syz.9.7569 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/06/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1be kernel/locking/lockdep.c:2087
 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2219
 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209
 check_prevs_add kernel/locking/lockdep.c:3328 [inline]
 validate_chain kernel/locking/lockdep.c:3952 [inline]
 __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288
 lock_acquire kernel/locking/lockdep.c:5942 [inline]
 lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
 down_write+0x86/0x1f0 kernel/locking/rwsem.c:1631
 i_mmap_lock_write include/linux/fs.h:508 [inline]
 dup_mmap+0xb09/0x2180 mm/mmap.c:1802
 dup_mm kernel/fork.c:1549 [inline]
 copy_mm kernel/fork.c:1602 [inline]
 copy_process+0x7c5c/0x88e0 kernel/fork.c:2328
 kernel_clone+0x176/0x9d0 kernel/fork.c:2798
 __do_sys_clone+0xd9/0x120 kernel/fork.c:2940
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x7b0 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f421cfa94d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f421de4afd8 EFLAGS: 00000206 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007f421d225fa0 RCX: 00007f421cfa94d9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000002820000
RBP: 00007f421d03804e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f421d226038 R14: 00007f421d225fa0 R15: 00007ffe923e2998
 </TASK>


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