wifi: ath11k: decrease MHI channel buffer length to 8KB

Summary

In the Linux kernel, the following vulnerability has been resolved: wifi: ath11k: decrease MHI channel buffer length to 8KB Currently buf_len field of ath11k_mhi_config_qca6390 is assigned with 0, making MHI use a default size, 64KB, to allocate channel buffers. This is likely to fail in some scenarios where system memory is highly fragmented and memory compaction or reclaim is not allowed. There is a fail report which is caused by it: kworker/u32:45: page allocation failure: order:4, mode:0x40c00(GFP_NOIO|__GFP_COMP), nodemask=(null),cpuset=/,mems_allowed=0 CPU: 0 PID: 19318 Comm: kworker/u32:45 Not tainted 6.8.0-rc3-1.gae4495f-default #1 openSUSE Tumbleweed (unreleased) 493b6d5b382c603654d7a81fc3c144d59a1dfceb Workqueue: events_unbound async_run_entry_fn Call Trace: <TASK> dump_stack_lvl+0x47/0x60 warn_alloc+0x13a/0x1b0 ? srso_alias_return_thunk+0x5/0xfbef5 ? __alloc_pages_direct_compact+0xab/0x210 __alloc_pages_slowpath.constprop.0+0xd3e/0xda0 __alloc_pages+0x32d/0x350 ? mhi_prepare_channel+0x127/0x2d0 [mhi 40df44e07c05479f7a6e7b90fba9f0e0031a7814] __kmalloc_large_node+0x72/0x110 __kmalloc+0x37c/0x480 ? mhi_map_single_no_bb+0x77/0xf0 [mhi 40df44e07c05479f7a6e7b90fba9f0e0031a7814] ? mhi_prepare_channel+0x127/0x2d0 [mhi 40df44e07c05479f7a6e7b90fba9f0e0031a7814] mhi_prepare_channel+0x127/0x2d0 [mhi 40df44e07c05479f7a6e7b90fba9f0e0031a7814] __mhi_prepare_for_transfer+0x44/0x80 [mhi 40df44e07c05479f7a6e7b90fba9f0e0031a7814] ? __pfx_____mhi_prepare_for_transfer+0x10/0x10 [mhi 40df44e07c05479f7a6e7b90fba9f0e0031a7814] device_for_each_child+0x5c/0xa0 ? __pfx_pci_pm_resume+0x10/0x10 ath11k_core_resume+0x65/0x100 [ath11k a5094e22d7223135c40d93c8f5321cf09fd85e4e] ? srso_alias_return_thunk+0x5/0xfbef5 ath11k_pci_pm_resume+0x32/0x60 [ath11k_pci 830b7bfc3ea80ebef32e563cafe2cb55e9cc73ec] ? srso_alias_return_thunk+0x5/0xfbef5 dpm_run_callback+0x8c/0x1e0 device_resume+0x104/0x340 ? __pfx_dpm_watchdog_handler+0x10/0x10 async_resume+0x1d/0x30 async_run_entry_fn+0x32/0x120 process_one_work+0x168/0x330 worker_thread+0x2f5/0x410 ? __pfx_worker_thread+0x10/0x10 kthread+0xe8/0x120 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x34/0x50 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1b/0x30 </TASK> Actually those buffers are used only by QMI target -> host communication. And for WCN6855 and QCA6390, the largest packet size for that is less than 6KB. So change buf_len field to 8KB, which results in order 1 allocation if page size is 4KB. In this way, we can at least save some memory, and as well as decrease the possibility of allocation failure in those scenarios. Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3.6510.30