nouveau: lock the client object tree.

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

nouveau: lock the client object tree.

It appears the client object tree has no locking unless I've missed
something else. Fix races around adding/removing client objects,
mostly vram bar mappings.

4562.099306] general protection fault, probably for non-canonical address 0x6677ed422bceb80c: 0000 [#1] PREEMPT SMP PTI
[ 4562.099314] CPU: 2 PID: 23171 Comm: deqp-vk Not tainted 6.8.0-rc6+ #27
[ 4562.099324] Hardware name: Gigabyte Technology Co., Ltd. Z390 I AORUS PRO WIFI/Z390 I AORUS PRO WIFI-CF, BIOS F8 11/05/2021
[ 4562.099330] RIP: 0010:nvkm_object_search+0x1d/0x70 [nouveau]
[ 4562.099503] Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 66 0f 1f 00 0f 1f 44 00 00 48 89 f8 48 85 f6 74 39 48 8b 87 a0 00 00 00 48 85 c0 74 12 <48> 8b 48 f8 48 39 ce 73 15 48 8b 40 10 48 85 c0 75 ee 48 c7 c0 fe
[ 4562.099506] RSP: 0000:ffffa94cc420bbf8 EFLAGS: 00010206
[ 4562.099512] RAX: 6677ed422bceb814 RBX: ffff98108791f400 RCX: ffff9810f26b8f58
[ 4562.099517] RDX: 0000000000000000 RSI: ffff9810f26b9158 RDI: ffff98108791f400
[ 4562.099519] RBP: ffff9810f26b9158 R08: 0000000000000000 R09: 0000000000000000
[ 4562.099521] R10: ffffa94cc420bc48 R11: 0000000000000001 R12: ffff9810f02a7cc0
[ 4562.099526] R13: 0000000000000000 R14: 00000000000000ff R15: 0000000000000007
[ 4562.099528] FS: 00007f629c5017c0(0000) GS:ffff98142c700000(0000) knlGS:0000000000000000
[ 4562.099534] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 4562.099536] CR2: 00007f629a882000 CR3: 000000017019e004 CR4: 00000000003706f0
[ 4562.099541] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 4562.099542] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 4562.099544] Call Trace:
[ 4562.099555] <TASK>
[ 4562.099573] ? die_addr+0x36/0x90
[ 4562.099583] ? exc_general_protection+0x246/0x4a0
[ 4562.099593] ? asm_exc_general_protection+0x26/0x30
[ 4562.099600] ? nvkm_object_search+0x1d/0x70 [nouveau]
[ 4562.099730] nvkm_ioctl+0xa1/0x250 [nouveau]
[ 4562.099861] nvif_object_map_handle+0xc8/0x180 [nouveau]
[ 4562.099986] nouveau_ttm_io_mem_reserve+0x122/0x270 [nouveau]
[ 4562.100156] ? dma_resv_test_signaled+0x26/0xb0
[ 4562.100163] ttm_bo_vm_fault_reserved+0x97/0x3c0 [ttm]
[ 4562.100182] ? __mutex_unlock_slowpath+0x2a/0x270
[ 4562.100189] nouveau_ttm_fault+0x69/0xb0 [nouveau]
[ 4562.100356] __do_fault+0x32/0x150
[ 4562.100362] do_fault+0x7c/0x560
[ 4562.100369] __handle_mm_fault+0x800/0xc10
[ 4562.100382] handle_mm_fault+0x17c/0x3e0
[ 4562.100388] do_user_addr_fault+0x208/0x860
[ 4562.100395] exc_page_fault+0x7f/0x200
[ 4562.100402] asm_exc_page_fault+0x26/0x30
[ 4562.100412] RIP: 0033:0x9b9870
[ 4562.100419] Code: 85 a8 f7 ff ff 8b 8d 80 f7 ff ff 89 08 e9 18 f2 ff ff 0f 1f 84 00 00 00 00 00 44 89 32 e9 90 fa ff ff 0f 1f 84 00 00 00 00 00 <44> 89 32 e9 f8 f1 ff ff 0f 1f 84 00 00 00 00 00 66 44 89 32 e9 e7
[ 4562.100422] RSP: 002b:00007fff9ba2dc70 EFLAGS: 00010246
[ 4562.100426] RAX: 0000000000000004 RBX: 000000000dd65e10 RCX: 000000fff0000000
[ 4562.100428] RDX: 00007f629a882000 RSI: 00007f629a882000 RDI: 0000000000000066
[ 4562.100432] RBP: 00007fff9ba2e570 R08: 0000000000000000 R09: 0000000123ddf000
[ 4562.100434] R10: 0000000000000001 R11: 0000000000000246 R12: 000000007fffffff
[ 4562.100436] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
[ 4562.100446] </TASK>
[ 4562.100448] Modules linked in: nf_conntrack_netbios_ns nf_conntrack_broadcast nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set nf_tables libcrc32c nfnetlink cmac bnep sunrpc iwlmvm intel_rapl_msr intel_rapl_common snd_sof_pci_intel_cnl x86_pkg_temp_thermal intel_powerclamp snd_sof_intel_hda_common mac80211 coretemp snd_soc_acpi_intel_match kvm_intel snd_soc_acpi snd_soc_hdac_hda snd_sof_pci snd_sof_xtensa_dsp snd_sof_intel_hda_mlink
---truncated---