[PATCH 0/8] Fix missing fops.owner in Rust DRM/misc abstractions

[Alvin Sun <alvin.sun@linux.dev>]

During tyr debugfs development, a kernel NULL pointer dereference was
encountered after `rmmod tyr` while gnome-shell still held /dev/card1 open:

```
  [158827.868132] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
  [158827.868918] Mem abort info:
  [158827.869177]   ESR = 0x0000000086000004
  [158827.869519]   EC = 0x21: IABT (current EL), IL = 32 bits
  [158827.870000]   SET = 0, FnV = 0
  [158827.870281]   EA = 0, S1PTW = 0
  [158827.870571]   FSC = 0x04: level 0 translation fault
  [158827.871043] user pgtable: 4k pages, 48-bit VAs, pgdp=0000000108dec000
  [158827.871623] [0000000000000000] pgd=0000000000000000, p4d=0000000000000000
  [158827.872242] Internal error: Oops: 0000000086000004 [#1]  SMP
  [158827.872246] Modules linked in: tyr sunrpc snd_soc_simple_card rk805_pwrkey snd_soc_simple_card_utils rtw88_8822bu display_connector rtw88_usb rtw88_8822b snd_soc_rockchip_i2s_tdm snd_soc_hdmi_codec
  rtw88_core]
  [158827.872337] CPU: 4 UID: 1000 PID: 11276 Comm: gnome-s:disk$0 Tainted: G                 N  7.1.0-rc1+ #331 PREEMPT
  [158827.880534] Tainted: [N]=TEST
  [158827.880535] Hardware name: FriendlyElec NanoPi R6C/NanoPi R6C, BIOS v1.1 04/09/2025
  [158827.880538] pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
  [158827.880542] pc : 0x0
  [158827.880547] lr : _RNvNtCs257m05FHVbX_3tyr2vm8pt_unmap+0x8c/0x12c [tyr]
  [158827.880578] sp : ffff800083c236b0
  [158827.880579] x29: ffff800083c236d0 x28: ffff00013f8a0000 x27: 0000000000000000
  [158827.880585] x26: 000000000000007c x25: ffff000108e6ed80 x24: 0000000000401000
  [158827.880590] x23: 0000000000000000 x22: 0000000040000000 x21: 0000000000001000
  [158827.880595] x20: ffff00010f778138 x19: 0000000000400000 x18: 00000000ffffffff
  [158827.880600] x17: 000000040044ffff x16: 045000f2b5503510 x15: 0720072007200720
  [158827.880606] x14: 0720072007200720 x13: 0000000000401000 x12: 0000000000400000
  [158827.880611] x11: ffff800083c239d0 x10: ffff000141e4fd88 x9 : 0000000000000000
  [158827.880615] x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000400000
  [158827.880620] x5 : ffff00013f8a0000 x4 : 0000000000000000 x3 : 0000000000000001
  [158827.880625] x2 : 0000000000001000 x1 : 0000000000400000 x0 : ffff00010f778138
  [158827.880630] Call trace:
  [158827.880632]  0x0 (P)
  [158827.880635]  _RNvXs6_NtCs257m05FHVbX_3tyr2vmNtB5_9GpuVmDataNtNtNtCsgmSOfgXi5CZ_6kernel3drm5gpuvm11DriverGpuVm13sm_step_unmap+0x3c/0x120 [tyr]
  [158827.891166]  _RNvMs4_NtNtNtCsgmSOfgXi5CZ_6kernel3drm5gpuvm6sm_opsINtB7_5GpuVmNtNtCs257m05FHVbX_3tyr2vm9GpuVmDataE13sm_step_unmapB13_+0x18/0x34 [tyr]
  [158827.891187]  op_unmap_cb+0x78/0xb0
  [158827.891196]  __drm_gpuvm_sm_unmap+0x18c/0x1b4
  [158827.891204]  drm_gpuvm_sm_unmap+0x38/0x4c
  [158827.891209]  _RNvMs5_NtCs257m05FHVbX_3tyr2vmNtB5_2Vm7exec_op+0x1cc/0x254 [tyr]
  [158827.894085]  _RNvMs5_NtCs257m05FHVbX_3tyr2vmNtB5_2Vm11unmap_range+0x124/0x188 [tyr]
  [158827.894105]  _RINvNtCs5hGKnPbRUFW_4core3ptr13drop_in_placeNtNtCs257m05FHVbX_3tyr3gem8KernelBoEBK_+0x44/0xd8 [tyr]
  [158827.894125]  _RINvNtCs5hGKnPbRUFW_4core3ptr13drop_in_placeINtNtNtCsgmSOfgXi5CZ_6kernel5alloc4kvec3VecNtNtCs257m05FHVbX_3tyr2fw7SectionNtNtBL_9allocator7KmallocEEB1r_+0x3c/0x100 [tyr]
  [158827.894147]  _RINvNtCs5hGKnPbRUFW_4core3ptr13drop_in_placeINtNtNtCsgmSOfgXi5CZ_6kernel4sync3arc3ArcNtNtCs257m05FHVbX_3tyr2fw8FirmwareEEB1p_+0x94/0x190 [tyr]
  [158827.894167]  _RNvMs4_NtNtCsgmSOfgXi5CZ_6kernel3drm6deviceINtB5_6DeviceNtNtCs257m05FHVbX_3tyr6driver12TyrDrmDriverE7releaseBW_+0x30/0x98 [tyr]
  [158827.899550]  drm_dev_put.part.0+0x88/0xc0
  [158827.899557]  drm_minor_release+0x18/0x28
  [158827.899562]  drm_release+0x144/0x170
  [158827.899567]  __fput+0xe4/0x30c
  [158827.899573]  ____fput+0x14/0x20
  [158827.899579]  task_work_run+0x7c/0xe8
  [158827.899586]  do_exit+0x2a8/0xac4
  [158827.899590]  do_group_exit+0x34/0x90
  [158827.899594]  get_signal+0xaac/0xabc
  [158827.899599]  arch_do_signal_or_restart+0x90/0x3e8
  [158827.899606]  exit_to_user_mode_loop+0x140/0x1d0
  [158827.899613]  el0_svc+0x2f4/0x2f8
  [158827.899620]  el0t_64_sync_handler+0xa0/0xe4
  [158827.899627]  el0t_64_sync+0x198/0x19c
  [158827.899632] ---[ end trace 0000000000000000 ]---
```

The root cause: fops.owner was NULL in Rust DRM drivers, so the kernel never
blocked module unloading while file descriptors were open. This leads to
use-after-free when drm_release (or other fops) is called on freed module code. 

The series adds MODULE_PTR to ModuleMetadata, threads ThisModule through the
DRM Driver trait into create_fops(), and applies the same fix to miscdevice.

Signed-off-by: Alvin Sun <alvin.sun@linux.dev>
---
Alvin Sun (8):
      rust: module: add `MODULE_PTR` const to `ModuleMetadata` trait
      rust: driver: make `DriverModule` struct pub(crate) in `module_driver!`
      rust: drm: add `ThisModule` associated type to `Driver` trait
      gpu: nova: implement `ThisModule`
      gpu: tyr: implement `ThisModule`
      rust: drm: set fops.owner from driver module pointer
      rust: miscdevice: add `ThisModule` associated type to `MiscDevice` trait
      samples: rust: rust_misc_device: implement `ThisModule` for `RustMiscDevice`

 drivers/gpu/drm/nova/driver.rs   |  1 +
 drivers/gpu/drm/tyr/driver.rs    |  1 +
 rust/kernel/driver.rs            |  2 +-
 rust/kernel/drm/device.rs        |  3 ++-
 rust/kernel/drm/driver.rs        |  3 +++
 rust/kernel/drm/gem/mod.rs       |  4 ++--
 rust/kernel/lib.rs               |  3 +++
 rust/kernel/miscdevice.rs        |  5 +++++
 rust/macros/module.rs            | 14 ++++++++++++++
 samples/rust/rust_misc_device.rs |  1 +
 10 files changed, 33 insertions(+), 4 deletions(-)
---
base-commit: aa61612ab641d7d62b0b6889f2c7c9251489f6e3
change-id: 20260519-fix-fops-owner-e3a77bb27c6c
prerequisite-change-id: 20260519-miscdev-use-format-9ab7e83b1c11:v1
prerequisite-patch-id: 405b334ff0d48ad350014f05a2321bdbaa025400
prerequisite-patch-id: 604b631c81d5423f4ebb2e12ba2d22e9ce371bfc

Best regards,
-- 
Alvin Sun <alvin.sun@linux.dev>