[PATCH] drm/radeon: Fix oops upon driver load on PowerXpress laptops

[Lukas Wunner]

On Mon, May 22, 2017 at 09:24:34PM +0200, Daniel Vetter wrote:
> On Thu, May 18, 2017 at 09:33:44PM +0200, Lukas Wunner wrote:
> > Nicolai Stange reports the following oops which is caused by
> > dereferencing rdev->pdev before it's subsequently set by
> > radeon_device_init().  Fix it.
> > 
> >   BUG: unable to handle kernel NULL pointer dereference at 00000000000007cb
> >   IP: radeon_driver_load_kms+0xeb/0x230 [radeon]
> >   PGD 0
> >   P4D 0
> > 
> >   Oops: 0000 [#1] SMP
> >   Modules linked in: amdkfd amd_iommu_v2 i915(+) radeon(+) i2c_algo_bit drm_kms_helper ttm e1000e drm sdhci_pci sdhci_acpi ptp sdhci crc32c_intel serio_raw mmc_core pps_core video i2c_hid hid_plantronics
> >   CPU: 4 PID: 389 Comm: systemd-udevd Not tainted 4.12.0-rc1-next-20170515+ #1
> >   Hardware name: Dell Inc. Latitude E6540/0725FP, BIOS A10 06/26/2014
> >   task: ffff97d62c8f0000 task.stack: ffffb96f01478000
> >   RIP: 0010:radeon_driver_load_kms+0xeb/0x230 [radeon]
> >   RSP: 0018:ffffb96f0147b9d0 EFLAGS: 00010246
> >   RAX: 0000000000000000 RBX: ffff97d620085000 RCX: 0000000000610037
> >   RDX: 0000000000000000 RSI: 000000000000002b RDI: 0000000000000000
> >   RBP: ffffb96f0147b9e8 R08: 0000000000000002 R09: ffffb96f0147b924
> >   R10: 0000000000000000 R11: ffff97d62edd2ec0 R12: ffff97d628d5c000
> >   R13: 0000000000610037 R14: ffffffffc0698280 R15: 0000000000000000
> >   FS:  00007f496363d8c0(0000) GS:ffff97d62eb00000(0000) knlGS:0000000000000000
> >   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >   CR2: 00000000000007cb CR3: 000000022c14c000 CR4: 00000000001406e0
> >   Call Trace:
> >    drm_dev_register+0x146/0x1d0 [drm]
> >    drm_get_pci_dev+0x9a/0x180 [drm]
> >    radeon_pci_probe+0xb8/0xe0 [radeon]
> >    local_pci_probe+0x45/0xa0
> >    pci_device_probe+0x14f/0x1a0
> >    driver_probe_device+0x29c/0x450
> >    __driver_attach+0xdf/0xf0
> >    ? driver_probe_device+0x450/0x450
> >    bus_for_each_dev+0x6c/0xc0
> >    driver_attach+0x1e/0x20
> >    bus_add_driver+0x170/0x270
> >    driver_register+0x60/0xe0
> >    ? 0xffffffffc0508000
> >    __pci_register_driver+0x4c/0x50
> >    drm_pci_init+0xeb/0x100 [drm]
> >    ? vga_switcheroo_register_handler+0x6a/0x90
> >    ? 0xffffffffc0508000
> >    radeon_init+0x98/0xb6 [radeon]
> >    do_one_initcall+0x52/0x1a0
> >    ? __vunmap+0x81/0xb0
> >    ? kmem_cache_alloc_trace+0x159/0x1b0
> >    ? do_init_module+0x27/0x1f8
> >    do_init_module+0x5f/0x1f8
> >    load_module+0x27ce/0x2be0
> >    SYSC_finit_module+0xdf/0x110
> >    ? SYSC_finit_module+0xdf/0x110
> >    SyS_finit_module+0xe/0x10
> >    do_syscall_64+0x67/0x150
> >    entry_SYSCALL64_slow_path+0x25/0x25
> >   RIP: 0033:0x7f4962295679
> >   RSP: 002b:00007ffdd8c4f878 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
> >   RAX: ffffffffffffffda RBX: 000055c014ed8200 RCX: 00007f4962295679
> >   RDX: 0000000000000000 RSI: 00007f4962dd19c5 RDI: 0000000000000010
> >   RBP: 00007f4962dd19c5 R08: 0000000000000000 R09: 00007ffdd8c4f990
> >   R10: 0000000000000010 R11: 0000000000000246 R12: 0000000000000000
> >   R13: 000055c014ed81a0 R14: 0000000000020000 R15: 000055c0149d1fca
> >   Code: 5d 5d c3 8b 05 a7 05 14 00 49 81 cd 00 00 08 00 85 c0 74 a3 e8 e7 c0 0e 00 84 c0 74 9a 41 f7 c5 00 00 02 00 75 91 49 8b 44 24 10 <0f> b6 90 cb 07 00 00 f6 c2 20 74 1e e9 7b ff ff ff 48 8b 40 38
> >   RIP: radeon_driver_load_kms+0xeb/0x230 [radeon] RSP: ffffb96f0147b9d0
> >   CR2: 00000000000007cb
> >   ---[ end trace 89cc4ba7e569c65c ]---
> > 
> > Reported-by: Nicolai Stange <nicstange at gmail.com>
> > Fixes: 7ffb0ce31cf9 ("drm/radeon: Don't register Thunderbolt eGPU with vga_switcheroo")
> > Signed-off-by: Lukas Wunner <lukas at wunner.de>
> > ---
> > 
> > Awaiting a Tested-by: from Nicolai, but it's clear this is a bug and
> > needs to be fixed, so sending out with a proper commit message now.
> > The bug was only introduced to radeon, not amdgpu.
> > 
> > @Alex Deucher: I could push this to drm-misc-fixes but then it wouldn't
> > land before -rc3 because Sean Paul has already sent out the -rc2 pull.
> > I notice you haven't sent out a pull for -rc2 yet, so maybe you want to
> > take it yourself?  Whichever you prefer.  Thanks & sorry for the breakage!
> 
> Just noticed that this has landed already in drm-misc-fixes, without any
> r-b or at least an ack from radeon driver folks. That's breaking the
> drm-misc rules, we need at least an ack for small drivers (which radeon
> really isn't) and a full reviewed-by tag on everything else.
> 
> Patch doesn't look wrong, so not much harm, but please follow the ground
> rules and especially don't ever push your own patches without any peer
> feedback.

I was aware of that rule and that the available peer feedback (Nicolai's
Tested-by) was thin.  I misinterpreted Christian's remark that he has
"all hands full replacing" Alex such that he is swamped in work and
didn't get the chance to look at my patch so far.  Christian was already
cc'ed on Nicolai's regression report and on every single e-mail that
followed.  I figured that nagging Christian wouldn't be helpful if he's
already overloaded, yet didn't want to miss another rc cycle, so I pushed
without waiting further for a response.  I'm sorry for the irritation this
has caused, I guess in the future nagging Christian despite regrets is the
only option in such a case.

Thanks,

Lukas