================================================ WARNING: lock held when returning to user space! 4.16.0+ #14 Not tainted ------------------------------------------------ syz-executor4/22948 is leaving the kernel with locks still held! 1 lock held by syz-executor4/22948: #0: 00000000e6bff8dd (&lo->lo_ctl_mutex/1){+.+.}, at: lo_ioctl+0x8d/0x1ec0 drivers/block/loop.c:1363 ================================================================== BUG: KASAN: use-after-free in mutex_can_spin_on_owner kernel/locking/mutex.c:479 [inline] BUG: KASAN: use-after-free in mutex_optimistic_spin kernel/locking/mutex.c:523 [inline] BUG: KASAN: use-after-free in __mutex_lock_common kernel/locking/mutex.c:759 [inline] BUG: KASAN: use-after-free in __mutex_lock+0x175f/0x17f0 kernel/locking/mutex.c:893 Read of size 4 at addr ffff8801b83226a0 by task syz-executor0/30015 CPU: 1 PID: 30015 Comm: syz-executor0 Not tainted 4.16.0+ #14 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1b9/0x294 lib/dump_stack.c:113 print_address_description+0x6c/0x20b mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report.cold.7+0xac/0x2f5 mm/kasan/report.c:412 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432 mutex_can_spin_on_owner kernel/locking/mutex.c:479 [inline] mutex_optimistic_spin kernel/locking/mutex.c:523 [inline] __mutex_lock_common kernel/locking/mutex.c:759 [inline] __mutex_lock+0x175f/0x17f0 kernel/locking/mutex.c:893 mutex_lock_killable_nested+0x16/0x20 kernel/locking/mutex.c:923 lo_ioctl+0x8d/0x1ec0 drivers/block/loop.c:1363 __blkdev_driver_ioctl block/ioctl.c:303 [inline] blkdev_ioctl+0x9b6/0x2020 block/ioctl.c:601 block_ioctl+0xee/0x130 fs/block_dev.c:1877 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:500 [inline] do_vfs_ioctl+0x1cf/0x1650 fs/ioctl.c:684 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701 SYSC_ioctl fs/ioctl.c:708 [inline] SyS_ioctl+0x24/0x30 fs/ioctl.c:706 do_syscall_64+0x29e/0x9d0 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x4550c7 RSP: 002b:00007ffdaac72e48 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000612 RCX: 00000000004550c7 RDX: 0000000000000000 RSI: 0000000000004c01 RDI: 0000000000000013 RBP: 0000000000000013 R08: 0000000000000000 R09: 000000000000000a R10: 0000000000000075 R11: 0000000000000246 R12: 0000000000000013 R13: 0000000000000000 R14: 00000000006fe800 R15: 0000000000001380 Allocated by task 22946: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490 kmem_cache_alloc_node+0x144/0x780 mm/slab.c:3644 alloc_task_struct_node kernel/fork.c:157 [inline] dup_task_struct kernel/fork.c:772 [inline] copy_process.part.38+0x16bf/0x6ee0 kernel/fork.c:1633 copy_process kernel/fork.c:1608 [inline] _do_fork+0x291/0x12a0 kernel/fork.c:2089 SYSC_clone kernel/fork.c:2196 [inline] SyS_clone+0x37/0x50 kernel/fork.c:2190 do_syscall_64+0x29e/0x9d0 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7 Freed by task 22959: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 __cache_free mm/slab.c:3498 [inline] kmem_cache_free+0x86/0x2d0 mm/slab.c:3756 free_task_struct kernel/fork.c:162 [inline] free_task+0x166/0x1d0 kernel/fork.c:391 __put_task_struct+0x2d2/0x600 kernel/fork.c:659 put_task_struct include/linux/sched/task.h:96 [inline] delayed_put_task_struct+0x367/0x470 kernel/exit.c:180 __rcu_reclaim kernel/rcu/rcu.h:178 [inline] rcu_do_batch kernel/rcu/tree.c:2675 [inline] invoke_rcu_callbacks kernel/rcu/tree.c:2930 [inline] __rcu_process_callbacks kernel/rcu/tree.c:2897 [inline] rcu_process_callbacks+0x941/0x15f0 kernel/rcu/tree.c:2914 __do_softirq+0x2e0/0xaf5 kernel/softirq.c:285 The buggy address belongs to the object at ffff8801b8322640 which belongs to the cache task_struct(113:syz4) of size 6016 The buggy address is located 96 bytes inside of 6016-byte region [ffff8801b8322640, ffff8801b8323dc0) The buggy address belongs to the page: page:ffffea0006e0c880 count:1 mapcount:0 mapping:ffff8801b8322640 index:0x0 compound_mapcount: 0 flags: 0x2fffc0000008100(slab|head) raw: 02fffc0000008100 ffff8801b8322640 0000000000000000 0000000100000001 raw: ffffea000733dea0 ffffea0006b340a0 ffff8801b0847980 ffff8801ac858000 page dumped because: kasan: bad access detected page->mem_cgroup:ffff8801ac858000 Memory state around the buggy address: ffff8801b8322580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8801b8322600: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb >ffff8801b8322680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8801b8322700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8801b8322780: fb fb 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