Subject: CVE-2024-35938: wifi: ath11k: decrease MHI channel buffer length to 8KB

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

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

The Linux kernel CVE team has assigned CVE-2024-35938 to this issue.

Affected and fixed versions
===========================

	Fixed in 5.15.155 with commit 805a1cdde82f
	Fixed in 6.1.86 with commit 6597a6687af5
	Fixed in 6.6.27 with commit 138fdeac75fb
	Fixed in 6.8.6 with commit ae5876b3b7b2
	Fixed in 6.9 with commit 1cca1bddf9ef

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-35938
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/net/wireless/ath/ath11k/mhi.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/805a1cdde82fec00c7471a393f4bb437b2741559
	https://git.kernel.org/stable/c/6597a6687af54e2cb58371cf8f6ee4dd85c537de
	https://git.kernel.org/stable/c/138fdeac75fb7512a7f9f1c3b236cd2e754af793
	https://git.kernel.org/stable/c/ae5876b3b7b2243d874e2afa099e7926122087a1
	https://git.kernel.org/stable/c/1cca1bddf9ef080503c15378cecf4877f7510015