It is a racy bug between l2cap_chan_timeout() and l2cap_sock_release() cause by SIGKILL. Sorry for the less context and no fix here. For the l2cap_sock.c in the stack trace, please refer this file for your convenience: https://gist.github.com/swkim101/5c3b8cb7c7d7172aef23810c9412f323 This is discovered by FuzzBT on top of Syzkaller with Sungwoo Kim (me). Other contributors for FuzzBT project are Ruoyu Wu(wuruoyu@xxxxxx) and Hui Peng(benquike@xxxxxxxxx). ================================================================== BUG: KASAN: use-after-free in l2cap_sock_kill (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/net/sock.h:986 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1281) Read of size 8 at addr ffff88800f7f4060 by task l2cap-server/1764 CPU: 0 PID: 1764 Comm: l2cap-server Not tainted 6.1.0-rc2 #129 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 Call Trace: <TASK> dump_stack_lvl (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/lib/dump_stack.c:105) print_address_description+0x7e/0x360 print_report (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/report.c:187 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/report.c:389) ? __virt_addr_valid (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/mmzone.h:1855 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/arch/x86/mm/physaddr.c:65) ? kasan_complete_mode_report_info (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/report_generic.c:104 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/report_generic.c:127 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/report_generic.c:136) ? l2cap_sock_kill (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/net/sock.h:986 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1281) kasan_report (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/report.c:? /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/report.c:484) ? l2cap_sock_kill (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/net/sock.h:986 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1281) kasan_check_range (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/generic.c:85 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/generic.c:115 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/generic.c:128 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/generic.c:159 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/generic.c:180 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/generic.c:189) __kasan_check_read (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/shadow.c:31) l2cap_sock_kill (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/net/sock.h:986 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1281) l2cap_sock_teardown_cb (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/net/bluetooth/bluetooth.h:304 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1475 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1612) l2cap_chan_close (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:885) ? __kasan_check_write (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/shadow.c:37) l2cap_sock_shutdown (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/kcsan-checks.h:231 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/net/sock.h:2470 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1321 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1377) ? _raw_write_unlock (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/asm-generic/qrwlock.h:122 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/rwlock_api_smp.h:225 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/locking/spinlock.c:342) l2cap_sock_release (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1453) sock_close (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/socket.c:1382) ? sock_mmap (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/socket.c:?) __fput (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/fsnotify.h:? /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/fsnotify.h:99 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/fsnotify.h:341 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/fs/file_table.c:306) ____fput (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/fs/file_table.c:348) task_work_run (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/task_work.c:165) do_exit (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/exit.c:?) do_group_exit (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/exit.c:943) ? __kasan_check_write (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/shadow.c:37) get_signal (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/signal.c:2863) ? _raw_spin_unlock (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/spinlock_api_smp.h:142 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/locking/spinlock.c:186) ? finish_task_switch (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./arch/x86/include/asm/current.h:15 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/sched/core.c:5065) arch_do_signal_or_restart (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/arch/x86/kernel/signal.c:869) exit_to_user_mode_prepare (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/entry/common.c:383) syscall_exit_to_user_mode (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./arch/x86/include/asm/current.h:15 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/entry/common.c:261 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/entry/common.c:283 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/entry/common.c:296) do_syscall_64 (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/arch/x86/entry/common.c:50 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/arch/x86/entry/common.c:80) ? sysvec_apic_timer_interrupt (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/arch/x86/kernel/apic/apic.c:1107) entry_SYSCALL_64_after_hwframe (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/arch/x86/entry/entry_64.S:120) RIP: 0033:0x7f66c14db970 Code: Unable to access opcode bytes at 0x7f66c14db946. Code starting with the faulting instruction =========================================== RSP: 002b:00007ffe166a5508 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: 0000000000000013 RBX: 0000000000000013 RCX: 00007f66c14db970 RDX: 0000000000000013 RSI: 00007ffe166a56d0 RDI: 0000000000000002 RBP: 00007ffe166a56d0 R08: 00007f66c1a28440 R09: 0000000000000013 R10: 0000000000000078 R11: 0000000000000246 R12: 0000000000000013 R13: 0000000000000001 R14: 00007f66c179a520 R15: 0000000000000013 </TASK> Allocated by task 77: kasan_set_track (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/common.c:51) kasan_save_alloc_info (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/generic.c:432 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/generic.c:498) __kasan_kmalloc (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/common.c:356) __kmalloc (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/slab_common.c:943 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/slab_common.c:968) sk_prot_alloc (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/core/sock.c:2028) sk_alloc (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/core/sock.c:2083) l2cap_sock_alloc (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1903) l2cap_sock_new_connection_cb (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1504) l2cap_connect (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:102 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:4277) l2cap_bredr_sig_cmd (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:5634 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:5927) l2cap_recv_frame (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:7851 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:7919) l2cap_recv_acldata (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:8601 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:8631) hci_rx_work (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/net/bluetooth/hci_core.h:1121 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/hci_core.c:3937 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/hci_core.c:4189) process_one_work (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:2225) worker_thread (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:816 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:2107 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:2159 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:2408) kthread (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/kthread.c:361) ret_from_fork (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/arch/x86/entry/entry_64.S:306) Freed by task 52: kasan_set_track (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/common.c:51) kasan_save_free_info (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/generic.c:508) ____kasan_slab_free (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/slub_def.h:164 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/common.c:214) __kasan_slab_free (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/kasan/common.c:244) slab_free_freelist_hook (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/slub.c:381 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/slub.c:1747) __kmem_cache_free (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/slub.c:3656 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/slub.c:3674) kfree (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/mm/slab_common.c:1007) __sk_destruct (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/cred.h:288 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/core/sock.c:2147) __sk_free (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/sock_diag.h:87 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/core/sock.c:2175) sk_free (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/instrumented.h:? /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/atomic/atomic-instrumented.h:176 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/refcount.h:272 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/refcount.h:315 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/linux/refcount.h:333 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/core/sock.c:2188) l2cap_sock_kill (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/net/bluetooth/bluetooth.h:286 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1284) l2cap_sock_close_cb (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_sock.c:1576) l2cap_chan_timeout (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/./include/net/bluetooth/bluetooth.h:296 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/net/bluetooth/l2cap_core.c:462) process_one_work (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:2225) worker_thread (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:816 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:2107 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:2159 /home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/workqueue.c:2408) kthread (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/kernel/kthread.c:361) ret_from_fork (/home/sungwoo/fuzzbt/v6.1-rc2-bzimage/arch/x86/entry/entry_64.S:306) The buggy address belongs to the object at ffff88800f7f4000 which belongs to the cache kmalloc-1k of size 1024 The buggy address is located 96 bytes inside of 1024-byte region [ffff88800f7f4000, ffff88800f7f4400) The buggy address belongs to the physical page: page:00000000b8d65c1d refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88800f7f6800 pfn:0xf7f4 head:00000000b8d65c1d order:2 compound_mapcount:0 compound_pincount:0 flags: 0xfffffc0010200(slab|head|node=0|zone=1|lastcpupid=0x1fffff) raw: 000fffffc0010200 ffffea0000993408 ffffea0000991308 ffff888005841dc0 raw: ffff88800f7f6800 0000000000080002 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88800f7f3f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff88800f7f3f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff >ffff88800f7f4000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88800f7f4080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88800f7f4100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================
