On 1/3/2025 1:43 AM, Shuo Liu wrote:
On Fri 3.Jan'25 at 15:02:38 +0800, Gerry Liu wrote:
2025年1月3日 13:58，Chen, Xiaogang <xiaogang.chen@xxxxxxx> 写道：
On 1/1/2025 11:36 PM, Jiang Liu wrote:
If some GPU device failed to probe, `rmmod amdgpu` will trigger a use
after free bug related to amdgpu_driver_release_kms() as:
2024-12-26 16:17:45 [16002.085540] BUG: kernel NULL pointer
dereference, address: 0000000000000000
2024-12-26 16:17:45 [16002.093792] #PF: supervisor read access in
kernel mode
2024-12-26 16:17:45 [16002.099993] #PF: error_code(0x0000) -
not-present page
2024-12-26 16:17:45 [16002.106188] PGD 0 P4D 0
2024-12-26 16:17:45 [16002.109464] Oops: Oops: 0000 [#1] PREEMPT
SMP NOPTI
2024-12-26 16:17:45 [16002.115372] CPU: 2 PID: 14375 Comm: rmmod
Kdump: loaded Tainted: G W E 6.10.0+ #2
2024-12-26 16:17:45 [16002.125577] Hardware name: Alibaba Alibaba
Cloud ECS/Alibaba Cloud ECS, BIOS 3.0.ES.AL.P.087.05 04/07/2024
2024-12-26 16:17:45 [16002.136858] RIP:
0010:drm_sched_fini+0x3f/0xe0 [gpu_sched]
2024-12-26 16:17:45 [16002.143463] Code: 60 c6 87 be 00 00 00 01 e8
ce e0 90 d8 48 8d bb 80 00 00 00 e8 c2 e0 90 d8 8b 43 20 85 c0 74
51 45 31 e4 48 8b
43 28 4d 63 ec <4a> 8b 2c e8 48 89 ef e8 f5 0e 59 d9 48 8b 45 10 48
8d 55 10 48 39
2024-12-26 16:17:45 [16002.164992] RSP: 0018:ffffb570dbbb7da8
EFLAGS: 00010246
2024-12-26 16:17:45 [16002.171316] RAX: 0000000000000000 RBX:
ffff96b0fdadc878 RCX: 0000000000000000
2024-12-26 16:17:46 [16002.179784] RDX: 000fffffffe00000 RSI:
0000000000000000 RDI: ffff96b0fdadc8f8
2024-12-26 16:17:46 [16002.188252] RBP: ffff96b0fdadc800 R08:
ffff97abbd035040 R09: ffffffff9ac52540
2024-12-26 16:17:46 [16002.196722] R10: 0000000000000000 R11:
0000000000000000 R12: 0000000000000000
2024-12-26 16:17:46 [16002.205179] R13: 0000000000000000 R14:
ffff96b0fdadfc00 R15: 0000000000000000
2024-12-26 16:17:46 [16002.213648] FS: 00007f2737000740(0000)
GS:ffff97abbd100000(0000) knlGS:0000000000000000
2024-12-26 16:17:46 [16002.223189] CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
2024-12-26 16:17:46 [16002.230103] CR2: 0000000000000000 CR3:
000000011be3a005 CR4: 0000000000f70ef0
2024-12-26 16:17:46 [16002.238581] DR0: 0000000000000000 DR1:
0000000000000000 DR2: 0000000000000000
2024-12-26 16:17:46 [16002.247053] DR3: 0000000000000000 DR6:
00000000fffe07f0 DR7: 0000000000000400
e024se+0x3c/0x90 [amdxcp]
2024-12-26 16:17:46 [16002.337645]
__do_sys_delete_module.constprop.0+0x176/0x310
2024-12-26 16:17:46 [16002.344324] do_syscall_64+0x5d/0x170
2024-12-26 16:17:46 [16002.348858]
entry_SYSCALL_64_after_hwframe+0x76/0x7e
2024-12-26 16:17:46 [16002.354956] RIP: 0033:0x7f2736a620cb-12-26
Fix it by unplugging xcp drm devices when failed to probe GPU devices.
Signed-off-by: Jiang Liu <gerry@xxxxxxxxxxxxxxxxx>
<mailto:gerry@xxxxxxxxxxxxxxxxx>
Tested-by: Shuo Liu <shuox.liu@xxxxxxxxxxxxxxxxx>
<mailto:shuox.liu@xxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c | 4 +++-
drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c | 1 +
2 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
index 5ffe1dad9622..e7f35e3a6d2d 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
@@ -164,8 +164,10 @@ int amdgpu_driver_load_kms(struct
amdgpu_device *adev, unsigned long flags)
DRM_WARN("smart shift update failed\n");
out:
- if (r)
+ if (r) {
+ amdgpu_xcp_dev_unplug(adev);
amdgpu_driver_unload_kms(dev);
+ }
I wonder if you can call amdgpu_xcp_dev_unplug here. It will call
drm_dev_unplug that unplugs a hotpluggable DRM device. In you case
amdgpu_driver_load_kms failed during probe time. We need unwind
amdgpu_driver_load_kms. Why need do unplug a DRM device?
The backtrace show:
2024-12-26 16:17:45 [16002.136858] RIP:
0010:drm_sched_fini+0x3f/0xe0 [gpu_sched]
has:
2024-12-26 16:17:45 [16002.085540] BUG: kernel NULL pointer
dereference, address: 0000000000000000
How this change is related to the invalid access above? Can you
explain more?
Per my understanding, `amdgpu_xcp_dev_unplug(adev)` is a workaround
for design flaw of the amdgpu_xcp driver.
Currently the amdgpu_xcp driver assumes everything will go as
expected and there’s no failure or GPU hot-lug operations.
So it only provides an interface `amdgpu_xcp_drm_dev_alloc()` to
create xcp devices for a GPU instance, and another interface
`amdgpu_xcp_drv_release()` to destroy xcp devices for GPU instances.
There’s no interface to undo what done by `amdgpu_xcp_drm_dev_alloc()`.
And I found `amdgpu_xcp_dev_unplug(adev)` can undo work done by
`amdgpu_xcp_drm_dev_alloc()`.
So it’s a workaround, the fundamental solution should be to enhance
amdgpu_xcp driver to provide interface to unroll work
done by `amdgpu_xcp_drm_dev_alloc()`.
Agree. Actually, some ops of amdgpu_partition_driver cannot be reused
directly by amd_xcp drm device. DRM doesn't use its minor->dev as
param of such callbacks, just like .release(). When
amdgpu_driver_release_kms() use a amd_xcp drm dev to find the `struct
amdgpu_device *adev`, unexcepted memory accesses.
I understand the issue is from xcp driver, but I do not see it is a
right workaround. The solution should be unwinding
amdgpu_xcp_drm_dev_alloc(), not unplug drm device though part of
amdgpu_xcp_dev_unplug(adev) may meet what you want.
still, the bracktrace has
2024-12-26 16:17:45 [16002.136858] RIP: 0010:drm_sched_fini+0x3f/0xe0
[gpu_sched]
How the root cause of that is from xcp driver?
Regards
Xiaogang
shuo
The code paths to trigger the use after free are:
1) in function amdgpu_xcp_dev_alloc(), we allocate a drm_device by
calling amdgpu_xcp_drm_dev_alloc(), and then change the device’s
driver to amdgpu_partition_driver.
2) in function amdgpu_xcp_dev_unplug(), it restores drm_device’s
driver to the original device driver.
In function amdgpu_driver_load_kms(), if we don’t call
amdgpu_xcp_dev_unplug() on error recover path, the
`xcp_dev[idx].driver` will still points to amdgpu_partition_driver.
Later when amdgpu_xcp_drv_release() gets called, it will call
platform_device_unregister() -> amdgpu_partition_driver.release ->
amdgpu_driver_release_kms().
Here when amdgpu_driver_release_kms() gets called, the corresponding
amdgpu_device object has already been released on error recovery path
in function amdgpu_pci_probe().
So just like amdgpu_pci_remove(), we call amdgpu_xcp_gpu_dev_unplug()
before calling amdkcl_drm_dev_release().
Regards
Xiaogang
return r;
}
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c
index a6d456ec6aeb..ef4eaacf67f6 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c
@@ -382,6 +382,7 @@ void amdgpu_xcp_dev_unplug(struct amdgpu_device
*adev)
p_ddev->primary->dev = adev->xcp_mgr->xcp[i].pdev;
p_ddev->driver = adev->xcp_mgr->xcp[i].driver;
p_ddev->vma_offset_manager =
adev->xcp_mgr->xcp[i].vma_offset_manager;
+ adev->xcp_mgr->xcp[i].ddev = NULL;
}
}
