Messages in this thread | | | Date | Mon, 28 May 2018 10:35:02 -0700 | Subject | Re: possible deadlock in bpf_tcp_close | From | syzbot <> |
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syzbot has found a reproducer for the following crash on:
HEAD commit: 7a1a98c171ea Merge branch 'bpf-sendmsg-hook' git tree: bpf-next console output: https://syzkaller.appspot.com/x/log.txt?x=149ae2b7800000 kernel config: https://syzkaller.appspot.com/x/.config?x=e4078980b886800c dashboard link: https://syzkaller.appspot.com/bug?extid=47ed903f50684f046b15 compiler: gcc (GCC) 8.0.1 20180413 (experimental) syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=1553b17b800000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1460be2f800000
IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+47ed903f50684f046b15@syzkaller.appspotmail.com
random: sshd: uninitialized urandom read (32 bytes read) random: sshd: uninitialized urandom read (32 bytes read) random: sshd: uninitialized urandom read (32 bytes read)
====================================================== WARNING: possible circular locking dependency detected 4.17.0-rc6+ #25 Not tainted ------------------------------------------------------ syz-executor800/4527 is trying to acquire lock: (ptrval) (&htab->buckets[i].lock){+...}, at: bpf_tcp_close+0x822/0x10b0 kernel/bpf/sockmap.c:285
but task is already holding lock: (ptrval) (clock-AF_INET6){++..}, at: bpf_tcp_close+0x241/0x10b0 kernel/bpf/sockmap.c:260
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (clock-AF_INET6){++..}: __raw_write_lock_bh include/linux/rwlock_api_smp.h:203 [inline] _raw_write_lock_bh+0x31/0x40 kernel/locking/spinlock.c:312 sock_hash_delete_elem+0x7c6/0xaf0 kernel/bpf/sockmap.c:2338 map_delete_elem+0x32e/0x4e0 kernel/bpf/syscall.c:815 __do_sys_bpf kernel/bpf/syscall.c:2349 [inline] __se_sys_bpf kernel/bpf/syscall.c:2317 [inline] __x64_sys_bpf+0x342/0x510 kernel/bpf/syscall.c:2317 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x49/0xbe
-> #0 (&htab->buckets[i].lock){+...}: lock_acquire+0x1dc/0x520 kernel/locking/lockdep.c:3920 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline] _raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:168 bpf_tcp_close+0x822/0x10b0 kernel/bpf/sockmap.c:285 inet_release+0x104/0x1f0 net/ipv4/af_inet.c:427 inet6_release+0x50/0x70 net/ipv6/af_inet6.c:459 sock_release+0x96/0x1b0 net/socket.c:594 sock_close+0x16/0x20 net/socket.c:1149 __fput+0x34d/0x890 fs/file_table.c:209 ____fput+0x15/0x20 fs/file_table.c:243 task_work_run+0x1e4/0x290 kernel/task_work.c:113 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0x1aee/0x2730 kernel/exit.c:865 do_group_exit+0x16f/0x430 kernel/exit.c:968 get_signal+0x886/0x1960 kernel/signal.c:2482 do_signal+0x98/0x2040 arch/x86/kernel/signal.c:810 exit_to_usermode_loop+0x28a/0x310 arch/x86/entry/common.c:162 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline] syscall_return_slowpath arch/x86/entry/common.c:265 [inline] do_syscall_64+0x6ac/0x800 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1 ---- ---- lock(clock-AF_INET6); lock(&htab->buckets[i].lock); lock(clock-AF_INET6); lock(&htab->buckets[i].lock);
*** DEADLOCK ***
2 locks held by syz-executor800/4527: #0: (ptrval) (rcu_read_lock){....}, at: bpf_tcp_close+0x0/0x10b0 kernel/bpf/sockmap.c:2106 #1: (ptrval) (clock-AF_INET6){++..}, at: bpf_tcp_close+0x241/0x10b0 kernel/bpf/sockmap.c:260
stack backtrace: CPU: 0 PID: 4527 Comm: syz-executor800 Not tainted 4.17.0-rc6+ #25 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_circular_bug.isra.36.cold.54+0x1bd/0x27d kernel/locking/lockdep.c:1223 check_prev_add kernel/locking/lockdep.c:1863 [inline] check_prevs_add kernel/locking/lockdep.c:1976 [inline] validate_chain kernel/locking/lockdep.c:2417 [inline] __lock_acquire+0x343e/0x5140 kernel/locking/lockdep.c:3431 lock_acquire+0x1dc/0x520 kernel/locking/lockdep.c:3920 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline] _raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:168 bpf_tcp_close+0x822/0x10b0 kernel/bpf/sockmap.c:285 inet_release+0x104/0x1f0 net/ipv4/af_inet.c:427 inet6_release+0x50/0x70 net/ipv6/af_inet6.c:459 sock_release+0x96/0x1b0 net/socket.c:594 sock_close+0x16/0x20 net/socket.c:1149 __fput+0x34d/0x890 fs/file_table.c:209 ____fput+0x15/0x20 fs/file_table.c:243 task_work_run+0x1e4/0x290 kernel/task_work.c:113 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0x1aee/0x2730 kernel/exit.c:865 do_group_exit+0x16f/0x430 kernel/exit.c:968 get_signal+0x886/0x1960 kernel/signal.c:2482 do_signal+0x98/0x2040 arch/x86/kernel/signal.c:810 exit_to_usermode_loop+0x28a/0x310 arch/x86/entry/common.c:162 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline] syscall_return_slowpath arch/x86/entry/common.c:265 [inline] do_syscall_64+0x6ac/0x800 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x445709 RSP: 002b:00007f36c605ddb8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca RAX: fffffffffffffe00 RBX: 00000000006dac3c RCX: 0000000000445709 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000006dac3c RBP: 00000000006dac38 R08: 0000000000000000 R09: 000
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