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  1. 12 4月, 2020 5 次提交
  3. 11 4月, 2020 5 次提交
  5. 10 4月, 2020 2 次提交
    • J
      io_uring: punt final io_ring_ctx wait-and-free to workqueue · 85faa7b8
      由 Jens Axboe 提交于 
      We can't reliably wait in io_ring_ctx_wait_and_kill(), since the
task_works list isn't ordered (in fact it's LIFO ordered). We could
either fix this with a separate task_works list for io_uring work, or
just punt the wait-and-free to async context. This ensures that
task_work that comes in while we're shutting down is processed
correctly. If we don't go async, we could have work past the fput()
work for the ring that depends on work that won't be executed until
after we're done with the wait-and-free. But as this operation is
blocking, it'll never get a chance to run.

This was reproduced with hundreds of thousands of sockets running
memcached, haven't been able to reproduce this synthetically.
Reported-by: NDan Melnic <dmm@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      85faa7b8
    • E
      proc: Use a dedicated lock in struct pid · 63f818f4
      由 Eric W. Biederman 提交于 
      syzbot wrote:
> ========================================================
> WARNING: possible irq lock inversion dependency detected
> 5.6.0-syzkaller #0 Not tainted
> --------------------------------------------------------
> swapper/1/0 just changed the state of lock:
> ffffffff898090d8 (tasklist_lock){.+.?}-{2:2}, at: send_sigurg+0x9f/0x320 fs/fcntl.c:840
> but this lock took another, SOFTIRQ-unsafe lock in the past:
>  (&pid->wait_pidfd){+.+.}-{2:2}
>
>
> and interrupts could create inverse lock ordering between them.
>
>
> other info that might help us debug this:
>  Possible interrupt unsafe locking scenario:
>
>        CPU0                    CPU1
>        ----                    ----
>   lock(&pid->wait_pidfd);
>                                local_irq_disable();
>                                lock(tasklist_lock);
>                                lock(&pid->wait_pidfd);
>   <Interrupt>
>     lock(tasklist_lock);
>
>  *** DEADLOCK ***
>
> 4 locks held by swapper/1/0:

The problem is that because wait_pidfd.lock is taken under the tasklist
lock.  It must always be taken with irqs disabled as tasklist_lock can be
taken from interrupt context and if wait_pidfd.lock was already taken this
would create a lock order inversion.

Oleg suggested just disabling irqs where I have added extra calls to
wait_pidfd.lock.  That should be safe and I think the code will eventually
do that.  It was rightly pointed out by Christian that sharing the
wait_pidfd.lock was a premature optimization.

It is also true that my pre-merge window testing was insufficient.  So
remove the premature optimization and give struct pid a dedicated lock of
it's own for struct pid things.  I have verified that lockdep sees all 3
paths where we take the new pid->lock and lockdep does not complain.

It is my current day dream that one day pid->lock can be used to guard the
task lists as well and then the tasklist_lock won't need to be held to
deliver signals.  That will require taking pid->lock with irqs disabled.
Acked-by: NChristian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/lkml/00000000000011d66805a25cd73f@google.com/
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Reported-by: syzbot+343f75cdeea091340956@syzkaller.appspotmail.com
Reported-by: syzbot+832aabf700bc3ec920b9@syzkaller.appspotmail.com
Reported-by: syzbot+f675f964019f884dbd0f@syzkaller.appspotmail.com
Reported-by: syzbot+a9fb1457d720a55d6dc5@syzkaller.appspotmail.com
Fixes: 7bc3e6e5 ("proc: Use a list of inodes to flush from proc")
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>
      63f818f4
  7. 09 4月, 2020 1 次提交
  9. 08 4月, 2020 26 次提交
  11. 07 4月, 2020 1 次提交
    • X
      io_uring: initialize fixed_file_data lock · f7fe9346
      由 Xiaoguang Wang 提交于 
      syzbot reports below warning:
INFO: trying to register non-static key.
the code is fine but needs lockdep annotation.
turning off the locking correctness validator.
CPU: 1 PID: 7099 Comm: syz-executor897 Not tainted 5.6.0-next-20200406-syzkaller #0
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+0x188/0x20d lib/dump_stack.c:118
 assign_lock_key kernel/locking/lockdep.c:913 [inline]
 register_lock_class+0x1664/0x1760 kernel/locking/lockdep.c:1225
 __lock_acquire+0x104/0x4e00 kernel/locking/lockdep.c:4223
 lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0x8c/0xbf kernel/locking/spinlock.c:159
 io_sqe_files_register fs/io_uring.c:6599 [inline]
 __io_uring_register+0x1fe8/0x2f00 fs/io_uring.c:8001
 __do_sys_io_uring_register fs/io_uring.c:8081 [inline]
 __se_sys_io_uring_register fs/io_uring.c:8063 [inline]
 __x64_sys_io_uring_register+0x192/0x560 fs/io_uring.c:8063
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x440289
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 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 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffff1bbf558 EFLAGS: 00000246 ORIG_RAX: 00000000000001ab
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440289
RDX: 0000000020000280 RSI: 0000000000000002 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000401b10
R13: 0000000000401ba0 R14: 0000000000000000 R15: 0000000000000000

Initialize struct fixed_file_data's lock to fix this issue.

Reported-by: syzbot+e6eeca4a035da76b3065@syzkaller.appspotmail.com
Fixes: 05589553 ("io_uring: refactor file register/unregister/update handling")
Signed-off-by: NXiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      f7fe9346