CVE-2022-48876: linux kernel Null Dereference — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: wifi: mac80211: fix initialization of rx->link and rx->link_sta There are some codepaths that do not initialize rx->link_sta properly. This causes a crash in places which assume that rx->link_sta is valid if rx->sta is valid. One known instance is triggered by __ieee80211_rx_h_amsdu being called from fast-rx. It results in a crash like this one: BUG: kernel NULL pointer dereference, address: 00000000000000a8 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] PREEMPT SMP PTI CPU: 1 PID: 506 Comm: mt76-usb-rx phy Tainted: G E 6.1.0-debian64x+1.7 #3 Hardware name: ZOTAC ZBOX-ID92/ZBOX-IQ01/ZBOX-ID92/ZBOX-IQ01, BIOS B220P007 05/21/2014 RIP: 0010:ieee80211_deliver_skb+0x62/0x1f0 [mac80211] Code: 00 48 89 04 24 e8 9e a7 c3 df 89 c0 48 03 1c c5 a0 ea 39 a1 4c 01 6b 08 48 ff 03 48 83 7d 28 00 74 11 48 8b 45 30 48 63 55 44 <48> 83 84 d0 a8 00 00 00 01 41 8b 86 c0 11 00 00 8d 50 fd 83 fa 01 RSP: 0018:ffff999040803b10 EFLAGS: 00010286 RAX: 0000000000000000 RBX: ffffb9903f496480 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffff999040803ce0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8d21828ac900 R13: 000000000000004a R14: ffff8d2198ed89c0 R15: ffff8d2198ed8000 FS: 0000000000000000(0000) GS:ffff8d24afe80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000000000a8 CR3: 0000000429810002 CR4: 00000000001706e0 Call Trace: <TASK> __ieee80211_rx_h_amsdu+0x1b5/0x240 [mac80211] ? ieee80211_prepare_and_rx_handle+0xcdd/0x1320 [mac80211] ? __local_bh_enable_ip+0x3b/0xa0 ieee80211_prepare_and_rx_handle+0xcdd/0x1320 [mac80211] ? prepare_transfer+0x109/0x1a0 [xhci_hcd] ieee80211_rx_list+0xa80/0xda0 [mac80211] mt76_rx_complete+0x207/0x2e0 [mt76] mt76_rx_poll_complete+0x357/0x5a0 [mt76] mt76u_rx_worker+0x4f5/0x600 [mt76_usb] ? mt76_get_min_avg_rssi+0x140/0x140 [mt76] __mt76_worker_fn+0x50/0x80 [mt76] kthread+0xed/0x120 ? kthread_complete_and_exit+0x20/0x20 ret_from_fork+0x22/0x30 Since the initialization of rx->link and rx->link_sta is rather convoluted and duplicated in many places, clean it up by using a helper function to set it. [remove unnecessary rx->sta->sta.mlo check]

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CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness Type (CWE)

CWE-476 CWE-476

Affected Products

Vendor	Product	Versions
linux	linux_kernel	6.1 — 6.1.8

References

Advisories & Patches

https://git.kernel.org/stable/c/a57c981d9f24d2bd89eaa76dc477e8ca252e22e8 https://git.kernel.org/stable/c/e66b7920aa5ac5b1a1997a454004ba9246a3c005

Frequently Asked Questions

What is CVE-2022-48876? +

In the Linux kernel, the following vulnerability has been resolved: wifi: mac80211: fix initialization of rx->link and rx->link_sta There are some codepaths that do not initialize rx->link_sta properly. This causes a crash in places which assume that rx->link_sta is valid if rx->sta is valid. One known instance is triggered by __ieee80211_rx_h_amsdu being called from fast-rx. It results in a crash like this one: BUG: kernel NULL pointer dereference, address: 00000000000000a8 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] PREEMPT SMP PTI CPU: 1 PID: 506 Comm: mt76-usb-rx phy Tainted: G E 6.1.0-debian64x+1.7 #3 Hardware name: ZOTAC ZBOX-ID92/ZBOX-IQ01/ZBOX-ID92/ZBOX-IQ01, BIOS B220P007 05/21/2014 RIP: 0010:ieee80211_deliver_skb+0x62/0x1f0 [mac80211] Code: 00 48 89 04 24 e8 9e a7 c3 df 89 c0 48 03 1c c5 a0 ea 39 a1 4c 01 6b 08 48 ff 03 48 83 7d 28 00 74 11 48 8b 45 30 48 63 55 44 <48> 83 84 d0 a8 00 00 00 01 41 8b 86 c0 11 00 00 8d 50 fd 83 fa 01 RSP: 0018:ffff999040803b10 EFLAGS: 00010286 RAX: 0000000000000000 RBX: ffffb9903f496480 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffff999040803ce0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8d21828ac900 R13: 000000000000004a R14: ffff8d2198ed89c0 R15: ffff8d2198ed8000 FS: 0000000000000000(0000) GS:ffff8d24afe80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000000000a8 CR3: 0000000429810002 CR4: 00000000001706e0 Call Trace: <TASK> __ieee80211_rx_h_amsdu+0x1b5/0x240 [mac80211] ? ieee80211_prepare_and_rx_handle+0xcdd/0x1320 [mac80211] ? __local_bh_enable_ip+0x3b/0xa0 ieee80211_prepare_and_rx_handle+0xcdd/0x1320 [mac80211] ? prepare_transfer+0x109/0x1a0 [xhci_hcd] ieee80211_rx_list+0xa80/0xda0 [mac80211] mt76_rx_complete+0x207/0x2e0 [mt76] mt76_rx_poll_complete+0x357/0x5a0 [mt76] mt76u_rx_worker+0x4f5/0x600 [mt76_usb] ? mt76_get_min_avg_rssi+0x140/0x140 [mt76] __mt76_worker_fn+0x50/0x80 [mt76] kthread+0xed/0x120 ? kthread_complete_and_exit+0x20/0x20 ret_from_fork+0x22/0x30 Since the initialization of rx->link and rx->link_sta is rather convoluted and duplicated in many places, clean it up by using a helper function to set it. [remove unnecessary rx->sta->sta.mlo check] It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2022-48876? +

CVE-2022-48876 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2022-48876? +

CVE-2022-48876 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2022-48876? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2022-48876