Re: [PATCH 1/2] drm/exynos: fix null pointer dereference issue

[Inki Dae <inki.dae@samsung.com>]

On 2014년 11월 21일 08:12, Gustavo Padovan wrote:
> 2014-11-13 Inki Dae <inki.dae@samsung.com>:
> 
>> This patch fixes null pointer dereference issue incurred
>> when ipp driver is enabled and Exynos drm driver is closed.
>>
>> Non kms driver should register its own sub driver to setup necessary
>> resources, which is done by load(). So null pointer dereference
>> occurs when ipp driver is enabled and Exynos drm driver is closed
>> because ipp core device is registered after component_master_add_with_match
>> call.
>>
>> This patch makes exynos_drm_device_subdrv_probe() to be called after all non
>> kms drivers are registered.
> 
> This patch is breaking exynos initialization, exynos_drm_device_subdrv_probe()
> needs the drvdata but it is still NULL at this point which make the whole
> exynos init fails. The drvdata is only set in exynos_drm_load() so we need
> call exynos_drm_device_subdrv_probe() after that.

There might be my missing point but with this patch,
exynos_drm_device_subdrv_probe() will be called after exynos_drm_load()
call because all kms drivers are probed before
component_master_add_with_match call so exynos_drm_load() must be called
by component_master_add_with_match function before
exynos_drm_device_subdrv_probe call.

So could you show me the error messages you faced with? There might be a
corner case I missed.

> 
> Do you have the crash output for this? What is the issue you are fixing?

Ok, below is the error messages,
# modetest
[    5.653291] ------------[ cut here ]------------
[    5.656469] WARNING: CPU: 2 PID: 1404 at kernel/locking/mutex.c:511
__mutex_lock_slowpath+0x3d4/0x3d8()
[    5.665816] DEBUG_LOCKS_WARN_ON(l->magic != l)
[    5.670069] Modules linked in:
[    5.673286] CPU: 2 PID: 1404 Comm: modetest Not tainted
3.18.0-rc3-146775-gbcfef97 #1149
[    5.681389] [<c0014400>] (unwind_backtrace) from [<c0011570>]
(show_stack+0x10/0x14)
[    5.689090] [<c0011570>] (show_stack) from [<c0474060>]
(dump_stack+0x84/0xc4)
[    5.696304] [<c0474060>] (dump_stack) from [<c0021918>]
(warn_slowpath_common+0x6c/0x88)
[    5.704364] [<c0021918>] (warn_slowpath_common) from [<c0021964>]
(warn_slowpath_fmt+0x30/0x40)
[    5.713047] [<c0021964>] (warn_slowpath_fmt) from [<c0477a4c>]
(__mutex_lock_slowpath+0x3d4/0x3d8)
[    5.721984] [<c0477a4c>] (__mutex_lock_slowpath) from [<c0477a5c>]
(mutex_lock+0xc/0x24)
[    5.730069] [<c0477a5c>] (mutex_lock) from [<c028e6fc>]
(ipp_subdrv_close+0x4c/0x13c)
[    5.737881] [<c028e6fc>] (ipp_subdrv_close) from [<c027a51c>]
(exynos_drm_subdrv_close+0x3c/0x4c)
[    5.746731] [<c027a51c>] (exynos_drm_subdrv_close) from [<c025eadc>]
(drm_release+0x94/0x4c8)
[    5.755228] [<c025eadc>] (drm_release) from [<c00cbdd4>]
(__fput+0x80/0x1c8)
[    5.762268] [<c00cbdd4>] (__fput) from [<c0037840>]
(task_work_run+0xac/0xe4)
[    5.769382] [<c0037840>] (task_work_run) from [<c00110f8>]
(do_work_pending+0x94/0xb4)
[    5.777275] [<c00110f8>] (do_work_pending) from [<c000e6e0>]
(work_pending+0xc/0x20)
[    5.784994] ---[ end trace bb48a41ae89d1f25 ]---
[    5.789598] Unable to handle kernel NULL pointer dereference at
virtual address 00000000
[    5.797664] pgd = ee3b8000
[    5.800354] [00000000] *pgd=6e366831, *pte=00000000, *ppte=00000000
[    5.806610] Internal error: Oops: 817 [#1] PREEMPT SMP ARM
[    5.812074] Modules linked in:
[    5.815117] CPU: 2 PID: 1404 Comm: modetest Tainted: G        W
3.18.0-rc3-146775-gbcfef97 #1149
[    5.824314] task: eea90800 ti: ee33c000 task.ti: ee33c000
[    5.829704] PC is at __mutex_lock_slowpath+0xf4/0x3d8
[    5.834730] LR is at __mutex_lock_slowpath+0xdc/0x3d8
[    5.839765] pc : [<c047776c>]    lr : [<c0477754>]    psr: 80000093
[    5.839765] sp : ee33de88  ip : ee33de98  fp : c06cb814
[    5.851220] r10: ee0f5854  r9 : c0700784  r8 : eea90800
[    5.856429] r7 : ee33c008  r6 : 60000013  r5 : ee0f5844  r4 : ee0f5840
[    5.862938] r3 : 00000000  r2 : 00000000  r1 : ee33de88  r0 : ee0f5840
[    5.869451] Flags: Nzcv  IRQs off  FIQs on  Mode SVC_32  ISA ARM
Segment user
[    5.876654] Control: 10c5387d  Table: 6e3b804a  DAC: 00000015
[    5.882383] Process modetest (pid: 1404, stack limit = 0xee33c240)
[    5.888544] Stack: (0xee33de88 to 0xee33e000)
[    5.892888] de80:                   ee0f5854 00000000 11111111
ee33de88 0001d030 ee0f5840
[    5.901048] dea0: c06b1d94 ee0f5810 c0705e4c ee0eeb00 00000000
ee0f5840 ee0f5810 c0477a5c
[    5.909207] dec0: eeb4a510 c028e6fc ee14a434 eeb4a510 c06b2fe4
ee14a400 ee33c000 eeb4a510
[    5.917366] dee0: c06b1d94 ee0eeb00 ee14a400 ee14a434 00000008
ee0eea08 00000000 c027a51c
[    5.925525] df00: c0705e4c ee0eeb00 ee0eea00 ee14a400 ee14a434
c025eadc ee0eea08 00000001
[    5.933684] df20: eebce000 00000000 00000000 00000000 00000021
ee0eea00 ee3354e0 00000000
[    5.941843] df40: ee32a250 ee711428 00000008 ee0eea08 00000000
c00cbdd4 00000000 00000000
[    5.950002] df60: eea90b4c 00000000 c06ca604 eea90800 c000e824
ee33c000 00000000 c0037840
[    5.958161] df80: ee33c018 c000e824 ee33dfb0 ee33c000 c000e824
c00110f8 00000003 00000001
[    5.966320] dfa0: beff0a4c 00000006 c000e824 c000e6e0 00000000
0001d000 00000003 0001d000
[    5.974479] dfc0: 00000003 00000001 beff0a4c 00000006 00000000
00000000 00000000 00000000
[    5.982639] dfe0: 00000000 beff09a4 b6f74257 b6eef626 40000030
00000003 00000000 00000000
[    5.990807] [<c047776c>] (__mutex_lock_slowpath) from [<c0477a5c>]
(mutex_lock+0xc/0x24)
[    5.998883] [<c0477a5c>] (mutex_lock) from [<c028e6fc>]
(ipp_subdrv_close+0x4c/0x13c)
[    6.006693] [<c028e6fc>] (ipp_subdrv_close) from [<c027a51c>]
(exynos_drm_subdrv_close+0x3c/0x4c)
[    6.015546] [<c027a51c>] (exynos_drm_subdrv_close) from [<c025eadc>]
(drm_release+0x94/0x4c8)
[    6.024047] [<c025eadc>] (drm_release) from [<c00cbdd4>]
(__fput+0x80/0x1c8)
[    6.031082] [<c00cbdd4>] (__fput) from [<c0037840>]
(task_work_run+0xac/0xe4)
[    6.038200] [<c0037840>] (task_work_run) from [<c00110f8>]
(do_work_pending+0x94/0xb4)
[    6.046094] [<c00110f8>] (do_work_pending) from [<c000e6e0>]
(work_pending+0xc/0x20)
[    6.053816] Code: e284a014 e584d018 e58da000 e58d3004 (e583d000)
[    6.059892] ---[ end trace bb48a41ae89d1f26 ]---

Thanks,
Inki Dae

> Usually you should add this kind of information to you commit message, it
> helps us understand what you are fixing, specially in cases when a regression
> is introduced, like this patch for example
> 
> 	Gustavo
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