drm/nouveau: prime: fix ttm_bo_delayed_delete oops

In the Linux kernel, the following vulnerability has been resolved:

drm/nouveau: prime: fix ttm_bo_delayed_delete oops

Fix an oops in ttm_bo_delayed_delete which results from dererencing a

dangling pointer:

Oops: general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b7b: 0000 [#1] PREEMPT SMP

CPU: 4 UID: 0 PID: 1082 Comm: kworker/u65:2 Not tainted 6.14.0-rc4-00267-g505460b44513-dirty #216

Hardware name: LENOVO 82N6/LNVNB161216, BIOS GKCN65WW 01/16/2024

Workqueue: ttm ttm_bo_delayed_delete [ttm]

RIP: 0010:dma_resv_iter_first_unlocked+0x55/0x290

Code: 31 f6 48 c7 c7 00 2b fa aa e8 97 bd 52 ff e8 a2 c1 53 00 5a 85 c0 74 48 e9 88 01 00 00 4c 89 63 20 4d 85 e4 0f 84 30 01 00 00 <41> 8b 44 24 10 c6 43 2c 01 48 89 df 89 43 28 e8 97 fd ff ff 4c 8b

RSP: 0018:ffffbf9383473d60 EFLAGS: 00010202

RAX: 0000000000000001 RBX: ffffbf9383473d88 RCX: 0000000000000000

RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000

RBP: ffffbf9383473d78 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000000 R12: 6b6b6b6b6b6b6b6b

R13: ffffa003bbf78580 R14: ffffa003a6728040 R15: 00000000000383cc

FS: 0000000000000000(0000) GS:ffffa00991c00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000758348024dd0 CR3: 000000012c259000 CR4: 0000000000f50ef0

PKRU: 55555554

Call Trace:

<TASK>

? __die_body.cold+0x19/0x26

? die_addr+0x3d/0x70

? exc_general_protection+0x159/0x460

? asm_exc_general_protection+0x27/0x30

? dma_resv_iter_first_unlocked+0x55/0x290

dma_resv_wait_timeout+0x56/0x100

ttm_bo_delayed_delete+0x69/0xb0 [ttm]

process_one_work+0x217/0x5c0

worker_thread+0x1c8/0x3d0

? apply_wqattrs_cleanup.part.0+0xc0/0xc0

kthread+0x10b/0x240

? kthreads_online_cpu+0x140/0x140

ret_from_fork+0x40/0x70

? kthreads_online_cpu+0x140/0x140

ret_from_fork_asm+0x11/0x20

</TASK>

The cause of this is:

- drm_prime_gem_destroy calls dma_buf_put(dma_buf) which releases the

reference to the shared dma_buf. The reference count is 0, so the

dma_buf is destroyed, which in turn decrements the corresponding

amdgpu_bo reference count to 0, and the amdgpu_bo is destroyed -

calling drm_gem_object_release then dma_resv_fini (which destroys the

reservation object), then finally freeing the amdgpu_bo.

- nouveau_bo obj->bo.base.resv is now a dangling pointer to the memory

formerly allocated to the amdgpu_bo.

- nouveau_gem_object_del calls ttm_bo_put(&nvbo->bo) which calls

ttm_bo_release, which schedules ttm_bo_delayed_delete.

- ttm_bo_delayed_delete runs and dereferences the dangling resv pointer,

resulting in a general protection fault.

Fix this by moving the drm_prime_gem_destroy call from

nouveau_gem_object_del to nouveau_bo_del_ttm. This ensures that it will

be run after ttm_bo_delayed_delete.