wifi: brcmfmac: Check the count value of channel spec to prevent out-of-bounds reads
CVE: CVE-2022-49740
Component: kernel
CWE: CWE-125
Severity: Moderate
CVSS v3: 7.4/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Release date: 2022-01-01T00:00:00+00:00

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

wifi: brcmfmac: Check the count value of channel spec to prevent out-of-bounds reads

This patch fixes slab-out-of-bounds reads in brcmfmac that occur in
brcmf_construct_chaninfo() and brcmf_enable_bw40_2g() when the count
value of channel specifications provided by the device is greater than
the length of 'list->element[]', decided by the size of the 'list'
allocated with kzalloc(). The patch adds checks that make the functions
free the buffer and return -EINVAL if that is the case. Note that the
negative return is handled by the caller, brcmf_setup_wiphybands() or
brcmf_cfg80211_attach().

Found by a modified version of syzkaller.

Crash Report from brcmf_construct_chaninfo():
==================================================================
BUG: KASAN: slab-out-of-bounds in brcmf_setup_wiphybands+0x1238/0x1430
Read of size 4 at addr ffff888115f24600 by task kworker/0:2/1896

CPU: 0 PID: 1896 Comm: kworker/0:2 Tainted: G        W  O      5.14.0+ #132
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014
Workqueue: usb_hub_wq hub_event
Call Trace:
 dump_stack_lvl+0x57/0x7d
 print_address_description.constprop.0.cold+0x93/0x334
 kasan_report.cold+0x83/0xdf
 brcmf_setup_wiphybands+0x1238/0x1430
 brcmf_cfg80211_attach+0x2118/0x3fd0
 brcmf_attach+0x389/0xd40
 brcmf_usb_probe+0x12de/0x1690
 usb_probe_interface+0x25f/0x710
 really_probe+0x1be/0xa90
 __driver_probe_device+0x2ab/0x460
 driver_probe_device+0x49/0x120
 __device_attach_driver+0x18a/0x250
 bus_for_each_drv+0x123/0x1a0
 __device_attach+0x207/0x330
 bus_probe_device+0x1a2/0x260
 device_add+0xa61/0x1ce0
 usb_set_configuration+0x984/0x1770
 usb_generic_driver_probe+0x69/0x90
 usb_probe_device+0x9c/0x220
 really_probe+0x1be/0xa90
 __driver_probe_device+0x2ab/0x460
 driver_probe_device+0x49/0x120
 __device_attach_driver+0x18a/0x250
 bus_for_each_drv+0x123/0x1a0
 __device_attach+0x207/0x330
 bus_probe_device+0x1a2/0x260
 device_add+0xa61/0x1ce0
 usb_new_device.cold+0x463/0xf66
 hub_event+0x10d5/0x3330
 process_one_work+0x873/0x13e0
 worker_thread+0x8b/0xd10
 kthread+0x379/0x450
 ret_from_fork+0x1f/0x30

Allocated by task 1896:
 kasan_save_stack+0x1b/0x40
 __kasan_kmalloc+0x7c/0x90
 kmem_cache_alloc_trace+0x19e/0x330
 brcmf_setup_wiphybands+0x290/0x1430
 brcmf_cfg80211_attach+0x2118/0x3fd0
 brcmf_attach+0x389/0xd40
 brcmf_usb_probe+0x12de/0x1690
 usb_probe_interface+0x25f/0x710
 really_probe+0x1be/0xa90
 __driver_probe_device+0x2ab/0x460
 driver_probe_device+0x49/0x120
 __device_attach_driver+0x18a/0x250
 bus_for_each_drv+0x123/0x1a0
 __device_attach+0x207/0x330
 bus_probe_device+0x1a2/0x260
 device_add+0xa61/0x1ce0
 usb_set_configuration+0x984/0x1770
 usb_generic_driver_probe+0x69/0x90
 usb_probe_device+0x9c/0x220
 really_probe+0x1be/0xa90
 __driver_probe_device+0x2ab/0x460
 driver_probe_device+0x49/0x120
 __device_attach_driver+0x18a/0x250
 bus_for_each_drv+0x123/0x1a0
 __device_attach+0x207/0x330
 bus_probe_device+0x1a2/0x260
 device_add+0xa61/0x1ce0
 usb_new_device.cold+0x463/0xf66
 hub_event+0x10d5/0x3330
 process_one_work+0x873/0x13e0
 worker_thread+0x8b/0xd10
 kthread+0x379/0x450
 ret_from_fork+0x1f/0x30

The buggy address belongs to the object at ffff888115f24000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1536 bytes inside of
 2048-byte region [ffff888115f24000, ffff888115f24800)

Memory state around the buggy address:
 ffff888115f24500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888115f24580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888115f24600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                   ^
 ffff888115f24680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888115f24700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crash Report from brcmf_enable_bw40_2g():
==========
---truncated---


Remediation: