Messages in this thread | | | Subject | Re: [PATCH] drm: assure aux_dev is nonzero before using it | From | Tony Camuso <> | Date | Mon, 23 Sep 2019 11:03:35 -0400 |
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On 7/12/19 1:06 PM, Ville Syrjälä wrote: > On Fri, Jul 12, 2019 at 12:07:46PM -0400, Tony Camuso wrote: >> On 7/10/19 9:56 AM, Ville Syrjälä wrote: >>> On Wed, Jul 10, 2019 at 09:47:11AM -0400, Tony Camuso wrote: >>>> On 5/24/19 4:36 AM, Jani Nikula wrote: >>>>> On Thu, 23 May 2019, tcamuso <tcamuso@redhat.com> wrote: >>>>>> From Daniel Kwon <dkwon@redhat.com> >>>>>> >>>>>> 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. >>>>> >>>>> 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. >>>>> >>>>> >>>>> BR, >>>>> Jani. >>>> >>>> I have not been able to reproduce this problem. >>> >>> mknod /dev/foo c <drm_dp_aux major> 255 >>> cat /dev/foo >>> >>> should do it. >> >> How do I determine <drm_dp_aux major>? > > ls,file,stat. Take your pick. >
Problem here is I can't ls,file,stat /dev/foo until after it's created, but I need to know the drm_dp_aux major number befroe I can use mknod.
What am I missing here?
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