kernel test robot <rong.a.c...@intel.com> writes:
> FYI, we noticed the following commit (built with gcc-7):
>
> commit: 9cb54e254ca479ce636857a1fd1e1a3e9f8796b1 ("[PATCH net-next v4 4/6]
> xdp: Always use a devmap for XDP_REDIRECT to a device")
> url:
> https://github.com/0day-ci/linux/commits/Toke-H-iland-J-rgensen/xdp-Use-a-default-map-for-xdp_redirect-helper/20190409-161851
>
>
> in testcase: trinity
> with following parameters:
>
> runtime: 300s
>
> test-description: Trinity is a linux system call fuzz tester.
> test-url: http://codemonkey.org.uk/projects/trinity/
>
>
> on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 8G
>
> caused below changes (please refer to attached dmesg/kmsg for entire
> log/backtrace):
>
>
> +--------------------------------------------------------------+------------+------------+
> | | c76c665440 |
> 9cb54e254c |
> +--------------------------------------------------------------+------------+------------+
> | boot_successes | 0 |
> 0 |
> | boot_failures | 40 |
> 38 |
> | BUG:kernel_reboot-without-warning_in_test_stage | 28 |
> 10 |
> | BUG:kernel_hang_in_boot_stage | 12 |
> 12 |
> | WARNING:suspicious_RCU_usage | 0 |
> 16 |
> | kernel/bpf/devmap.c:#suspicious_rcu_dereference_check()usage | 0 |
> 16 |
> +--------------------------------------------------------------+------------+------------+
>
>
>
> [ 413.653218] WARNING: suspicious RCU usage
> [ 413.654564] 5.1.0-rc4-00599-g9cb54e2 #43 Tainted: G T
> [ 413.656563] -----------------------------
> [ 413.657808] kernel/bpf/devmap.c:807 suspicious rcu_dereference_check()
> usage!
> [ 413.660285]
> [ 413.660285] other info that might help us debug this:
> [ 413.660285]
> [ 413.662614]
> [ 413.662614] rcu_scheduler_active = 2, debug_locks = 1
> [ 413.664483] 2 locks held by trinity-c3/2248:
> [ 413.665800] #0: 00000000713e8e50 (&f->f_pos_lock){+.+.}, at:
> __fdget_pos+0x81/0x90
> [ 413.668184] #1: 000000005e54a26c (&p->lock){+.+.}, at:
> seq_lseek+0x42/0x1c0
> [ 413.670412]
> [ 413.670412] stack backtrace:
> [ 413.671876] CPU: 0 PID: 2248 Comm: trinity-c3 Tainted: G T
> 5.1.0-rc4-00599-g9cb54e2 #43
> [ 413.674557] Call Trace:
> [ 413.675374] dump_stack+0x1e/0x28
> [ 413.676366] lockdep_rcu_suspicious+0xc6/0xd0
> [ 413.677802] dev_map_default_show+0x84/0xd0
Ah, right, seems I forgot an rcu_read_lock() here. Will fix :)
-Toke
