On 5/24/19 4:36 AM, Jani Nikula wrote:
On Thu, 23 May 2019, tcamuso <tcamuso@xxxxxxxxxx> wrote:From Daniel Kwon <dkwon@xxxxxxxxxx> The system was crashed due to invalid memory access while trying to access auxiliary device. crash> bt PID: 9863 TASK: ffff89d1bdf11040 CPU: 1 COMMAND: "ipmitool" #0 [ffff89cedd7f3868] machine_kexec at ffffffffb0663674 #1 [ffff89cedd7f38c8] __crash_kexec at ffffffffb071cf62 #2 [ffff89cedd7f3998] crash_kexec at ffffffffb071d050 #3 [ffff89cedd7f39b0] oops_end at ffffffffb0d6d758 #4 [ffff89cedd7f39d8] no_context at ffffffffb0d5bcde #5 [ffff89cedd7f3a28] __bad_area_nosemaphore at ffffffffb0d5bd75 #6 [ffff89cedd7f3a78] bad_area at ffffffffb0d5c085 #7 [ffff89cedd7f3aa0] __do_page_fault at ffffffffb0d7080c #8 [ffff89cedd7f3b10] do_page_fault at ffffffffb0d70905 #9 [ffff89cedd7f3b40] page_fault at ffffffffb0d6c758 [exception RIP: drm_dp_aux_dev_get_by_minor+0x3d] RIP: ffffffffc0a589bd RSP: ffff89cedd7f3bf0 RFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff89cedd7f3fd8 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffffc0a613e0 RBP: ffff89cedd7f3bf8 R8: ffff89f1bcbabbd0 R9: 0000000000000000 R10: ffff89f1be7a1cc0 R11: 0000000000000000 R12: 0000000000000000 R13: ffff89f1b32a2830 R14: ffff89d18fadfa00 R15: 0000000000000000 ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 RIP: 00002b45f0d80d30 RSP: 00007ffc416066a0 RFLAGS: 00010246 RAX: 0000000000000002 RBX: 000056062e212d80 RCX: 00007ffc41606810 RDX: 0000000000000000 RSI: 0000000000000002 RDI: 00007ffc41606ec0 RBP: 0000000000000000 R8: 000056062dfed229 R9: 00002b45f0cdf14d R10: 0000000000000002 R11: 0000000000000246 R12: 00007ffc41606ec0 R13: 00007ffc41606ed0 R14: 00007ffc41606ee0 R15: 0000000000000000 ORIG_RAX: 0000000000000002 CS: 0033 SS: 002b ---------------------------------------------------------------------------- It was trying to open '/dev/ipmi0', but as no entry in aux_dir, it returned NULL from 'idr_find()'. This drm_dp_aux_dev_get_by_minor() should have done a check on this, but had failed to do it.I think the better question is, *why* does the idr_find() return NULL? I don't think it should, under any circumstances. I fear adding the check here papers over some other problem, taking us further away from the root cause.
That's a very good question.
Also, can you reproduce this on a recent upstream kernel? The aux device nodes were introduced in kernel v4.6. Whatever you reproduced on v3.10 is pretty much irrelevant for upstream.
I will look into this deeper, using the upstream kernel.
BR, Jani.
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