Hello, I've got the following crash while running syzkaller on 093b995e3b55a0ae0670226ddfcb05bfbf0099ae. Note the preceding injected kmalloc failure, most likely it's the root cause.
FAULT_INJECTION: forcing a failure. name failslab, interval 1, probability 0, space 0, times 0 CPU: 1 PID: 4874 Comm: syz-executor3 Not tainted 4.11.0-rc3+ #364 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Call Trace: kzalloc include/linux/slab.h:495 [inline] register_shrinker+0x10e/0x2d0 mm/vmscan.c:284 sget_userns+0xbf2/0xe40 fs/super.c:521 mount_ns+0x6d/0x190 fs/super.c:1026 mqueue_mount+0xbe/0xe0 ipc/mqueue.c:340 mount_fs+0x66/0x2f0 fs/super.c:1223 vfs_kern_mount.part.23+0xc6/0x4b0 fs/namespace.c:979 vfs_kern_mount fs/namespace.c:3293 [inline] kern_mount_data+0x50/0xb0 fs/namespace.c:3293 mq_init_ns+0x167/0x220 ipc/mqueue.c:1418 create_ipc_ns ipc/namespace.c:57 [inline] copy_ipcs+0x39b/0x580 ipc/namespace.c:83 create_new_namespaces+0x285/0x8c0 kernel/nsproxy.c:86 unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:205 SYSC_unshare kernel/fork.c:2319 [inline] SyS_unshare+0x664/0xf80 kernel/fork.c:2269 entry_SYSCALL_64_fastpath+0x1f/0xc2 RIP: 0033:0x445b79 RSP: 002b:00007fb4faa4e858 EFLAGS: 00000286 ORIG_RAX: 0000000000000110 RAX: ffffffffffffffda RBX: 0000000000708000 RCX: 0000000000445b79 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000a040000 RBP: 0000000000000086 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000286 R12: 00000000004a7e31 R13: 0000000000000000 R14: 00007fb4faa4e618 R15: 00007fb4faa4e788 kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 1 PID: 4874 Comm: syz-executor3 Not tainted 4.11.0-rc3+ #364 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 task: ffff8800390760c0 task.stack: ffff880039228000 RIP: 0010:__list_del_entry_valid+0x7e/0x150 lib/list_debug.c:51 RSP: 0018:ffff88003922ef00 EFLAGS: 00010246 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffff88003a232ea0 RDI: ffff88003a232ea8 RBP: ffff88003922ef18 R08: fffffbfff0c0242c R09: 0000000000000001 R10: ffff8800390760c0 R11: fffffbfff0c0242b R12: 0000000000000000 R13: dffffc0000000000 R14: ffff88003a232740 R15: ffff88003a232ea0 FS: 00007fb4faa4f700(0000) GS:ffff88003fd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020000ff7 CR3: 0000000043a01000 CR4: 00000000000026e0 DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 Call Trace: __list_del_entry include/linux/list.h:116 [inline] list_del include/linux/list.h:124 [inline] unregister_shrinker+0x79/0x300 mm/vmscan.c:301 deactivate_locked_super+0x75/0xe0 fs/super.c:308 deactivate_super+0x151/0x160 fs/super.c:340 cleanup_mnt+0xb2/0x160 fs/namespace.c:1115 mntput_no_expire+0x6e9/0xaa0 fs/namespace.c:1181 mntput fs/namespace.c:1191 [inline] kern_unmount+0x9c/0xd0 fs/namespace.c:2995 mq_put_mnt+0x37/0x50 ipc/mqueue.c:1434 put_ipc_ns+0x4d/0x160 ipc/namespace.c:150 free_nsproxy+0xde/0x230 kernel/nsproxy.c:179 switch_task_namespaces+0xaa/0xc0 kernel/nsproxy.c:228 exit_task_namespaces+0x17/0x20 kernel/nsproxy.c:233 do_exit+0x1ac6/0x26d0 kernel/exit.c:878 do_group_exit+0x149/0x400 kernel/exit.c:983 get_signal+0x696/0x1810 kernel/signal.c:2318 do_signal+0x90/0x1ee0 arch/x86/kernel/signal.c:808 exit_to_usermode_loop+0x1e5/0x2d0 arch/x86/entry/common.c:157 prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline] syscall_return_slowpath+0x3bd/0x460 arch/x86/entry/common.c:260 entry_SYSCALL_64_fastpath+0xc0/0xc2 RIP: 0033:0x445b79 RSP: 002b:00007fb4faa4e858 EFLAGS: 00000202 ORIG_RAX: 00000000000000ca RAX: 0000000000000001 RBX: 0000000000708000 RCX: 0000000000445b79 RDX: 0000000000000009 RSI: 0000000000000001 RDI: 0000000000708024 RBP: 0000000000001d10 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 00000000006dfdd0 R13: 000000008208ae63 R14: 000000002000a000 R15: ffffffffffffffff Code: 00 00 00 00 ad de 49 39 c4 74 66 48 b8 00 02 00 00 00 00 ad de 48 89 da 48 39 c3 74 65 48 c1 ea 03 48 b8 00 00 00 00 00 fc ff df <80> 3c 02 00 75 7b 48 8b 13 48 39 f2 75 57 49 8d 7c 24 08 48 b8 RIP: __list_del_entry_valid+0x7e/0x150 lib/list_debug.c:51 RSP: ffff88003922ef00 ---[ end trace 569c84071b70c014 ]---
