WARNING: lock held when returning to user space! 4.20.0+ #396 Not tainted ------------------------------------------------ syz-executor0/29677 is leaving the kernel with locks still held! 1 lock held by syz-executor0/29677: #0: 00000000ec5f6915 (&type->s_umount_key#43){++++}, at: grab_super+0xcc/0x400 fs/super.c:383 kobject: 'loop5' (00000000edd59d60): kobject_uevent_env kobject: 'loop5' (00000000edd59d60): fill_kobj_path: path = '/devices/virtual/block/loop5' ================================================================== BUG: KASAN: use-after-free in owner_on_cpu kernel/locking/rwsem-xadd.c:367 [inline] BUG: KASAN: use-after-free in rwsem_can_spin_on_owner kernel/locking/rwsem-xadd.c:384 [inline] BUG: KASAN: use-after-free in rwsem_optimistic_spin kernel/locking/rwsem-xadd.c:437 [inline] BUG: KASAN: use-after-free in __rwsem_down_write_failed_common+0x14ea/0x15e0 kernel/locking/rwsem-xadd.c:518 Read of size 4 at addr ffff88805631c738 by task syz-executor0/29718 CPU: 0 PID: 29718 Comm: syz-executor0 Not tainted 4.20.0+ #396 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 kobject: 'loop2' (000000006e1a6a52): kobject_uevent_env Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1d3/0x2c6 lib/dump_stack.c:113 print_address_description.cold.5+0x9/0x1ff mm/kasan/report.c:187 kobject: 'loop2' (000000006e1a6a52): fill_kobj_path: path = '/devices/virtual/block/loop2' kasan_report.cold.6+0x1b/0x39 mm/kasan/report.c:317 kobject: 'loop1' (0000000042cf1ea5): kobject_uevent_env __asan_report_load4_noabort+0x14/0x20 mm/kasan/generic_report.c:134 owner_on_cpu kernel/locking/rwsem-xadd.c:367 [inline] rwsem_can_spin_on_owner kernel/locking/rwsem-xadd.c:384 [inline] rwsem_optimistic_spin kernel/locking/rwsem-xadd.c:437 [inline] __rwsem_down_write_failed_common+0x14ea/0x15e0 kernel/locking/rwsem-xadd.c:518 kobject: 'loop1' (0000000042cf1ea5): fill_kobj_path: path = '/devices/virtual/block/loop1' kobject: 'loop2' (000000006e1a6a52): kobject_uevent_env kobject: 'loop2' (000000006e1a6a52): fill_kobj_path: path = '/devices/virtual/block/loop2' rwsem_down_write_failed+0xe/0x10 kernel/locking/rwsem-xadd.c:606 call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:117 __down_write arch/x86/include/asm/rwsem.h:142 [inline] down_write+0xa5/0x130 kernel/locking/rwsem.c:72 kobject: 'loop5' (00000000edd59d60): kobject_uevent_env grab_super+0xcc/0x400 fs/super.c:383 kobject: 'loop5' (00000000edd59d60): fill_kobj_path: path = '/devices/virtual/block/loop5' sget_userns+0x435/0xed0 fs/super.c:511 kernfs_mount_ns+0x1d7/0xa80 fs/kernfs/mount.c:324 kernfs_mount include/linux/kernfs.h:554 [inline] cgroup_do_mount+0xc4/0x330 kernel/cgroup/cgroup.c:2038 cgroup_mount+0xb6d/0xd30 kernel/cgroup/cgroup.c:2102 mount_fs+0xae/0x31d fs/super.c:1261 vfs_kern_mount.part.35+0xdc/0x4f0 fs/namespace.c:961 vfs_kern_mount fs/namespace.c:951 [inline] do_new_mount fs/namespace.c:2469 [inline] do_mount+0x581/0x31f0 fs/namespace.c:2801 ksys_mount+0x12d/0x140 fs/namespace.c:3017 __do_sys_mount fs/namespace.c:3031 [inline] __se_sys_mount fs/namespace.c:3028 [inline] __x64_sys_mount+0xbe/0x150 fs/namespace.c:3028 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x457ec9 Code: 6d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fbd6c16dc78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 00007fbd6c16dc90 RCX: 0000000000457ec9 RDX: 0000000020000200 RSI: 0000000020000080 RDI: 0000000000000000 RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fbd6c16e6d4 R13: 00000000004c3a19 R14: 00000000004d64a8 R15: 0000000000000003 Allocated by task 29676: save_stack+0x43/0xd0 mm/kasan/common.c:73 set_track mm/kasan/common.c:85 [inline] kasan_kmalloc+0xcb/0xd0 mm/kasan/common.c:482 kasan_slab_alloc+0x12/0x20 mm/kasan/common.c:397 kmem_cache_alloc_node+0x147/0x730 mm/slab.c:3631 alloc_task_struct_node kernel/fork.c:158 [inline] dup_task_struct kernel/fork.c:849 [inline] copy_process+0x2027/0x8790 kernel/fork.c:1757 _do_fork+0x1cb/0x11d0 kernel/fork.c:2222 __do_sys_clone kernel/fork.c:2329 [inline] __se_sys_clone kernel/fork.c:2323 [inline] __x64_sys_clone+0xbf/0x150 kernel/fork.c:2323 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe Freed by task 29709: save_stack+0x43/0xd0 mm/kasan/common.c:73 set_track mm/kasan/common.c:85 [inline] __kasan_slab_free+0x102/0x150 mm/kasan/common.c:444 kasan_slab_free+0xe/0x10 mm/kasan/common.c:452 __cache_free mm/slab.c:3485 [inline] kmem_cache_free+0x83/0x290 mm/slab.c:3747 free_task_struct kernel/fork.c:163 [inline] free_task+0x16e/0x1f0 kernel/fork.c:462 __put_task_struct+0x2e6/0x620 kernel/fork.c:735 put_task_struct include/linux/sched/task.h:96 [inline] delayed_put_task_struct+0x2ff/0x4c0 kernel/exit.c:181 __rcu_reclaim kernel/rcu/rcu.h:240 [inline] rcu_do_batch kernel/rcu/tree.c:2452 [inline] invoke_rcu_callbacks kernel/rcu/tree.c:2773 [inline] rcu_process_callbacks+0xc5b/0x1600 kernel/rcu/tree.c:2754 __do_softirq+0x30c/0xb2e kernel/softirq.c:292 The buggy address belongs to the object at ffff88805631c700 which belongs to the cache task_struct(17:syz0) of size 6080 The buggy address is located 56 bytes inside of 6080-byte region [ffff88805631c700, ffff88805631dec0) The buggy address belongs to the page: page:ffffea000158c700 count:1 mapcount:0 mapping:ffff88808d959e40 index:0x0 compound_mapcount: 0 flags: 0x1fffc0000010200(slab|head) raw: 01fffc0000010200 ffffea00023f4688 ffffea0000394788 ffff88808d959e40 raw: 0000000000000000 ffff88805631c700 0000000100000001 ffff88805aa82c00 page dumped because: kasan: bad access detected page->mem_cgroup:ffff88805aa82c00 Memory state around the buggy address: ffff88805631c600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88805631c680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88805631c700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88805631c780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88805631c800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================