Re: [PATCH v2 00/10] drm/msm: probe deferral fixes
From: Steev Klimaszewski
Date: Tue Sep 13 2022 - 16:23:22 EST
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.
These bugs are not new but have become critical with the release of
5.19 where probe is deferred in case the aux-bus EP panel driver has not
yet been loaded.
The underlying problem is lifetime issues due to careless use of
device-managed resources.
Specifically, device-managed resources allocated post component bind
must be tied to the lifetime of the aggregate DRM device or they will
not necessarily be released when binding of the aggregate device is
deferred.
The following call chain and pseudo code serves as an illustration of
the problem:
- platform_probe(pdev1)
- dp_display_probe()
- component_add()
- platform_probe(pdev2) // last component
- dp_display_probe() // d0
- component_add()
- try_to_bring_up_aggregate_device()
- devres_open_group(adev->parent) // d1
- msm_drm_bind()
- msm_drm_init()
- component_bind_all()
- for_each_component()
- component_bind()
- devres_open_group(&pdev->dev) // d2
- dp_display_bind()
- devm_kzalloc(&pdev->dev) // a1, OK
- devres_close_group(&pdev->dev) // d3
- dpu_kms_hw_init()
- for_each_panel()
- msm_dp_modeset_init()
- dp_display_request_irq()
- devm_request_irq(&pdev->dev) // a2, BUG
- if (pdev == pdev2 && condition)
- return -EPROBE_DEFER;
- if (error)
- component_unbind_all()
- for_each_component()
- component_unbind()
- dp_display_unbind()
- devres_release_group(&pdev->dev) // d4, only a1 is freed
- if (error)
- devres_release_group(adev->parent) // d5
The device-managed allocation a2 is buggy as its lifetime is tied to the
component platform device and will not be released when the aggregate
device bind fails (e.g. due to a probe deferral).
When pdev2 is later probed again, the attempt to allocate the IRQ a
second time will fail for pdev1 (which is still bound to its platform
driver).
This series fixes the lifetime issues by tying the lifetime of a2 (and
similar allocations) to the lifetime of the aggregate device so that a2
is released at d5.
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.
Johan
Changes in v2
- use a custom devres action instead of amending the AUX bus interface
(Doug)
- split sanity check fixes and cleanups per bridge type (Dmitry)
- add another Fixes tag for the missing bridge counter reset (Dmitry)
Johan Hovold (10):
drm/msm: fix use-after-free on probe deferral
drm/msm/dp: fix memory corruption with too many bridges
drm/msm/dsi: fix memory corruption with too many bridges
drm/msm/hdmi: fix memory corruption with too many bridges
drm/msm/dp: fix IRQ lifetime
drm/msm/dp: fix aux-bus EP lifetime
drm/msm/dp: fix bridge lifetime
drm/msm/hdmi: fix IRQ lifetime
drm/msm/dp: drop modeset sanity checks
drm/msm/dsi: drop modeset sanity checks
drivers/gpu/drm/msm/dp/dp_display.c | 26 +++++++++++++++++++-------
drivers/gpu/drm/msm/dp/dp_parser.c | 6 +++---
drivers/gpu/drm/msm/dp/dp_parser.h | 5 +++--
drivers/gpu/drm/msm/dsi/dsi.c | 9 +++++----
drivers/gpu/drm/msm/hdmi/hdmi.c | 7 ++++++-
drivers/gpu/drm/msm/msm_drv.c | 1 +
6 files changed, 37 insertions(+), 17 deletions(-)
I've tested this on both sc8180x (Lenovo Flex 5G) and sdm850 (Lenovo
Yoga C630), and both of them show the same issue:
[ 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@xxxxxxxxxx/
applied here which makes the 10th patch not apply cleanly.
It fails actually, but I applied it manually here.