------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 0 PID: 27955 at lib/refcount.c:190 refcount_sub_and_test_checked lib/refcount.c:190 [inline] WARNING: CPU: 0 PID: 27955 at lib/refcount.c:190 refcount_sub_and_test_checked+0x1d0/0x200 lib/refcount.c:180 Kernel panic - not syncing: panic_on_warn set ... CPU: 0 PID: 27955 Comm: syz-executor.0 Not tainted 5.1.0-rc7+ #96 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+0x172/0x1f0 lib/dump_stack.c:113 panic+0x2cb/0x65c kernel/panic.c:214 __warn.cold+0x20/0x45 kernel/panic.c:571 report_bug+0x263/0x2b0 lib/bug.c:186 fixup_bug arch/x86/kernel/traps.c:179 [inline] fixup_bug arch/x86/kernel/traps.c:174 [inline] do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272 do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973 RIP: 0010:refcount_sub_and_test_checked lib/refcount.c:190 [inline] RIP: 0010:refcount_sub_and_test_checked+0x1d0/0x200 lib/refcount.c:180 Code: 1d c8 30 2a 06 31 ff 89 de e8 0c 32 40 fe 84 db 75 94 e8 c3 30 40 fe 48 c7 c7 60 79 a1 87 c6 05 a8 30 2a 06 01 e8 ae de 12 fe <0f> 0b e9 75 ff ff ff e8 a4 30 40 fe e9 6e ff ff ff 48 89 df e8 37 RSP: 0018:ffff8880a877f860 EFLAGS: 00010282 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000040000 RSI: ffffffff815afcb6 RDI: ffffed10150efefe RBP: ffff8880a877f8f8 R08: ffff8880550923c0 R09: ffffed1015d05011 R10: ffffed1015d05010 R11: ffff8880ae828087 R12: 00000000ffffffff R13: 0000000000000001 R14: ffff8880a877f8d0 R15: 0000000000000000 refcount_dec_and_test_checked+0x1b/0x20 lib/refcount.c:220 kref_put include/linux/kref.h:66 [inline] p9_req_put+0x20/0x60 net/9p/client.c:401 p9_conn_destroy net/9p/trans_fd.c:880 [inline] p9_fd_close+0x2ee/0x570 net/9p/trans_fd.c:913 p9_client_create+0x998/0x1400 net/9p/client.c:1083 v9fs_session_init+0x1e7/0x1960 fs/9p/v9fs.c:421 v9fs_mount+0x7d/0x920 fs/9p/vfs_super.c:135 legacy_get_tree+0xf2/0x200 fs/fs_context.c:584 vfs_get_tree+0x123/0x450 fs/super.c:1481 do_new_mount fs/namespace.c:2622 [inline] do_mount+0x1436/0x2c40 fs/namespace.c:2942 ksys_mount+0xdb/0x150 fs/namespace.c:3151 __do_sys_mount fs/namespace.c:3165 [inline] __se_sys_mount fs/namespace.c:3162 [inline] __x64_sys_mount+0xbe/0x150 fs/namespace.c:3162 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x458da9 Code: ad b8 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 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f6ad9a65c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 00007f6ad9a65c90 RCX: 0000000000458da9 RDX: 0000000020000100 RSI: 00000000200000c0 RDI: 0000000000000000 RBP: 000000000073bf00 R08: 00000000200013c0 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f6ad9a666d4 R13: 00000000004c4da7 R14: 00000000004d8a20 R15: 0000000000000005 Kernel Offset: disabled Rebooting in 86400 seconds..