Subject: CVE-2021-47540: mt76: mt7915: fix NULL pointer dereference in mt7915_get_phy_mode

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

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

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

mt76: mt7915: fix NULL pointer dereference in mt7915_get_phy_mode

Fix the following NULL pointer dereference in mt7915_get_phy_mode
routine adding an ibss interface to the mt7915 driver.

[  101.137097] wlan0: Trigger new scan to find an IBSS to join
[  102.827039] wlan0: Creating new IBSS network, BSSID 26:a4:50:1a:6e:69
[  103.064756] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
[  103.073670] Mem abort info:
[  103.076520]   ESR = 0x96000005
[  103.079614]   EC = 0x25: DABT (current EL), IL = 32 bits
[  103.084934]   SET = 0, FnV = 0
[  103.088042]   EA = 0, S1PTW = 0
[  103.091215] Data abort info:
[  103.094104]   ISV = 0, ISS = 0x00000005
[  103.098041]   CM = 0, WnR = 0
[  103.101044] user pgtable: 4k pages, 39-bit VAs, pgdp=00000000460b1000
[  103.107565] [0000000000000000] pgd=0000000000000000, p4d=0000000000000000, pud=0000000000000000
[  103.116590] Internal error: Oops: 96000005 [#1] SMP
[  103.189066] CPU: 1 PID: 333 Comm: kworker/u4:3 Not tainted 5.10.75 #0
[  103.195498] Hardware name: MediaTek MT7622 RFB1 board (DT)
[  103.201124] Workqueue: phy0 ieee80211_iface_work [mac80211]
[  103.206695] pstate: 20000005 (nzCv daif -PAN -UAO -TCO BTYPE=--)
[  103.212705] pc : mt7915_get_phy_mode+0x68/0x120 [mt7915e]
[  103.218103] lr : mt7915_mcu_add_bss_info+0x11c/0x760 [mt7915e]
[  103.223927] sp : ffffffc011cdb9e0
[  103.227235] x29: ffffffc011cdb9e0 x28: ffffff8006563098
[  103.232545] x27: ffffff8005f4da22 x26: ffffff800685ac40
[  103.237855] x25: 0000000000000001 x24: 000000000000011f
[  103.243165] x23: ffffff8005f4e260 x22: ffffff8006567918
[  103.248475] x21: ffffff8005f4df80 x20: ffffff800685ac58
[  103.253785] x19: ffffff8006744400 x18: 0000000000000000
[  103.259094] x17: 0000000000000000 x16: 0000000000000001
[  103.264403] x15: 000899c3a2d9d2e4 x14: 000899bdc3c3a1c8
[  103.269713] x13: 0000000000000000 x12: 0000000000000000
[  103.275024] x11: ffffffc010e30c20 x10: 0000000000000000
[  103.280333] x9 : 0000000000000050 x8 : ffffff8006567d88
[  103.285642] x7 : ffffff8006563b5c x6 : ffffff8006563b44
[  103.290952] x5 : 0000000000000002 x4 : 0000000000000001
[  103.296262] x3 : 0000000000000001 x2 : 0000000000000001
[  103.301572] x1 : 0000000000000000 x0 : 0000000000000011
[  103.306882] Call trace:
[  103.309328]  mt7915_get_phy_mode+0x68/0x120 [mt7915e]
[  103.314378]  mt7915_bss_info_changed+0x198/0x200 [mt7915e]
[  103.319941]  ieee80211_bss_info_change_notify+0x128/0x290 [mac80211]
[  103.326360]  __ieee80211_sta_join_ibss+0x308/0x6c4 [mac80211]
[  103.332171]  ieee80211_sta_create_ibss+0x8c/0x10c [mac80211]
[  103.337895]  ieee80211_ibss_work+0x3dc/0x614 [mac80211]
[  103.343185]  ieee80211_iface_work+0x388/0x3f0 [mac80211]
[  103.348495]  process_one_work+0x288/0x690
[  103.352499]  worker_thread+0x70/0x464
[  103.356157]  kthread+0x144/0x150
[  103.359380]  ret_from_fork+0x10/0x18
[  103.362952] Code: 394008c3 52800220 394000e4 7100007f (39400023)

The Linux kernel CVE team has assigned CVE-2021-47540 to this issue.

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

	Issue introduced in 5.8 with commit 37f4ca907c46 and fixed in 5.10.84 with commit 932b338f4e5c
	Issue introduced in 5.8 with commit 37f4ca907c46 and fixed in 5.15.7 with commit 14b03b8cebdf
	Issue introduced in 5.8 with commit 37f4ca907c46 and fixed in 5.16 with commit 6e53d6d26920

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-2021-47540
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/mediatek/mt76/mt7915/mcu.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/932b338f4e5c4cb0c2ed640da3bced1e63620198
	https://git.kernel.org/stable/c/14b03b8cebdf18ff13c39d58501b625411314de2
	https://git.kernel.org/stable/c/6e53d6d26920d5221d3f4d4f5ffdd629ea69aa5c