Re: [PATCH v2 00/10] drm/msm: probe deferral fixes

Steev Klimaszewski
2022-09-16T16:44:03Z

Hi Johan,

On Wed, Sep 14, 2022 at 1:01 AM Johan Hovold <johan@kernel.org> wrote:
>
> On Tue, Sep 13, 2022 at 03:23:10PM -0500, Steev Klimaszewski wrote:
> > Hi Johan,
> >
> > On 9/13/22 3:53 AM, Johan Hovold wrote:
> > > The MSM DRM driver is currently broken in multiple ways with respect to
> > > probe deferral. Not only does the driver currently fail to probe again
> > > after a late deferral, but due to a related use-after-free bug this also
> > > triggers NULL-pointer dereferences.
>
> > > In some cases, such has for the DP IRQ, the above situation can also be
> > > avoided by moving the allocation in question to the platform driver
> > > probe (d0) or component bind (between d2 and d3). But as doing so is not
> > > a general fix, this can be done later as a cleanup/optimisation.
>
> > I've tested this on both sc8180x (Lenovo Flex 5G) and sdm850 (Lenovo
> > Yoga C630), and both of them show the same issue:
>
> [ Copied the below from IRC instead as the formatting in your mail was
> off. ]
>
> > [ 7.449305] platform ae9a000.displayport-controller: Fixing up cyclic dependency with ae01000.mdp
> > [ 7.454344] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008
> > [ 7.454406] Mem abort info:
> > [ 7.454423] ESR = 0x0000000096000004
> > [ 7.454446] EC = 0x25: DABT (current EL), IL = 32 bits
> > [ 7.454475] SET = 0, FnV = 0
> > [ 7.454494] EA = 0, S1PTW = 0
> > [ 7.454512] FSC = 0x04: level 0 translation fault
> > [ 7.454539] Data abort info:
> > [ 7.454556] ISV = 0, ISS = 0x00000004
> > [ 7.454577] CM = 0, WnR = 0
> > [ 7.454595] user pgtable: 4k pages, 48-bit VAs, pgdp=0000000101504000
> > [ 7.454629] [0000000000000008] pgd=0000000000000000, p4d=0000000000000000
> > [ 7.454669] Internal error: Oops: 96000004 [#1] PREEMPT SMP
> > [ 7.454700] Modules linked in: i2c_hid_of i2c_hid leds_qcom_lpg led_class_multicolor rtc_pm8xxx msm mdt_loader gpu_sched drm_dp_aux_bus drm_display_helper drm_kms_helper drm phy_qcom_edp llcc_qcom i2c_qcom_geni phy_qcom_qmp_combo phy_qcom_snps_femto_v2 phy_qcom_qmp_ufs phy_qcom_qmp_pcie ufs_qcom pwm_bl
> > [ 7.454860] CPU: 2 PID: 76 Comm: kworker/u16:2 Not tainted 5.19.0-rc8-next-20220728 #26
> > [ 7.454902] Hardware name: LENOVO 82AK/LNVNB161216, BIOS EACN43WW(V1.15) 09/13/2021
> > [ 7.454941] Workqueue: events_unbound deferred_probe_work_func
> > [ 7.454982] pstate: 40400005 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> > [ 7.455020] pc : dp_display_request_irq+0x50/0xdc [msm]
> > [ 7.455145] lr : dp_display_request_irq+0x2c/0xdc [msm]
> > [ 7.455265] sp : ffff800008c1bb30
> > [ 7.455285] x29: ffff800008c1bb30 x28: 0000000000000000 x27: 0000000000000000
> > [ 7.455327] x26: ffffc9c918420000 x25: ffffc9c9186ec570 x24: 000000000000003a
> > [ 7.455368] x23: ffffc9c918811d30 x22: ffff2a5806baa998 x21: ffff2a5806ba3410
> > [ 7.455410] x20: ffff2a5806baa880 x19: ffff2a5806baa998 x18: ffffffffffffffff
> > [ 7.455451] x17: 0000000000000038 x16: ffffc9c9164eeb24 x15: ffffffffffffffff
> > [ 7.455492] x14: ffff2a5806bc3004 x13: ffff2a5806bc3000 x12: 0000000000000000
> > [ 7.455533] x11: 0000000000000040 x10: ffffc9c918493080 x9 : ffffc9c918493078
> > [ 7.455574] x8 : ffff2a5800681b88 x7 : 0000000000000000 x6 : ffff2a5806baa880
> > [ 7.455616] x5 : ffffc9c8ca2de000 x4 : 0000000000080004 x3 : 0000000000000000
> > [ 7.455656] x2 : ffffc9c8ca296000 x1 : 00000000000000a8 x0 : 0000000000000000
> > [ 7.455698] Call trace:
> > [ 7.455714] dp_display_request_irq+0x50/0xdc [msm]
> > [ 7.455834] dp_display_probe+0xf8/0x4a4 [msm]
> > [ 7.455950] platform_probe+0x6c/0xc4
> > [ 7.455976] really_probe+0xbc/0x2d4
> > [ 7.455999] __driver_probe_device+0x78/0xe0
> > [ 7.456025] driver_probe_device+0x3c/0x13c
> > [ 7.456051] __device_attach_driver+0xb8/0x120
> > [ 7.456077] bus_for_each_drv+0x78/0xd0
> > [ 7.456105] __device_attach+0x9c/0x1a0
> > [ 7.456129] device_initial_probe+0x18/0x2c
> > [ 7.456154] bus_probe_device+0x9c/0xa4
> > [ 7.456178] deferred_probe_work_func+0x88/0xc0
> > [ 7.456204] process_one_work+0x1d4/0x330
> > [ 7.456231] worker_thread+0x70/0x42c
> > [ 7.456255] kthread+0x10c/0x110
> > [ 7.456278] ret_from_fork+0x10/0x20
> > [ 7.456306] Code: aa1403e6 f2a00104 f0000225 f0ffffe2 (f9400400)
> > [ 7.456341] ---[ end trace 0000000000000000 ]---
>
> > This is from the sc8180x, sdm850 is the same call stack, just with
> > different addresses.
> >
> > I do have
> > https://lore.kernel.org/all/20220712132258.671263-1-dmitry.baryshkov@linaro.org/
> > applied here which makes the 10th patch not apply cleanly.
>
> Yeah, that is expected. You need to drop Dmitry's series first. Once you
> verified that this series works, you can add it back if you want but you
> then need to restore the device pointer used when allocating the irq in
> dp_display_request_irq():
>
> - rc = devm_request_irq(dp_display->drm_dev->dev, dp->irq,
> + rc = devm_request_irq(&dp->pdev->dev, dp->irq,
>
> > It fails actually, but I applied it manually here.
>
> Please drop that series and give this one another spin.
>
> Johan

I thought as much but wasn't sure. Thanks for the clarification.
With Dmitriy's patchset backed out, this series does work as expected.

Tested-by: Steev Klimaszewski <steev@kali.org>