wifi: iwlwifi: mvm: fix double free on tx path
CVE: CVE-2022-50248
Component: kernel
CWE: CWE-415
Severity: Moderate
CVSS v3: 6.6/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:H
Release date: 2022-01-01T00:00:00+00:00

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

wifi: iwlwifi: mvm: fix double free on tx path.

We see kernel crashes and lockups and KASAN errors related to ax210
firmware crashes.  One of the KASAN dumps pointed at the tx path,
and it appears there is indeed a way to double-free an skb.

If iwl_mvm_tx_skb_sta returns non-zero, then the 'skb' sent into the
method will be freed.  But, in case where we build TSO skb buffer,
the skb may also be freed in error case.  So, return 0 in that particular
error case and do cleanup manually.

BUG: KASAN: use-after-free in __list_del_entry_valid+0x12/0x90
iwlwifi 0000:06:00.0: 0x00000000 | tsf hi
Read of size 8 at addr ffff88813cfa4ba0 by task btserver/9650

CPU: 4 PID: 9650 Comm: btserver Tainted: G        W         5.19.8+ #5
iwlwifi 0000:06:00.0: 0x00000000 | time gp1
Hardware name: Default string Default string/SKYBAY, BIOS 5.12 02/19/2019
Call Trace:
 <TASK>
 dump_stack_lvl+0x55/0x6d
 print_report.cold.12+0xf2/0x684
iwlwifi 0000:06:00.0: 0x1D0915A8 | time gp2
 ? __list_del_entry_valid+0x12/0x90
 kasan_report+0x8b/0x180
iwlwifi 0000:06:00.0: 0x00000001 | uCode revision type
 ? __list_del_entry_valid+0x12/0x90
 __list_del_entry_valid+0x12/0x90
iwlwifi 0000:06:00.0: 0x00000048 | uCode version major
 tcp_update_skb_after_send+0x5d/0x170
 __tcp_transmit_skb+0xb61/0x15c0
iwlwifi 0000:06:00.0: 0xDAA05125 | uCode version minor
 ? __tcp_select_window+0x490/0x490
iwlwifi 0000:06:00.0: 0x00000420 | hw version
 ? trace_kmalloc_node+0x29/0xd0
 ? __kmalloc_node_track_caller+0x12a/0x260
 ? memset+0x1f/0x40
 ? __build_skb_around+0x125/0x150
 ? __alloc_skb+0x1d4/0x220
 ? skb_zerocopy_clone+0x55/0x230
iwlwifi 0000:06:00.0: 0x00489002 | board version
 ? kmalloc_reserve+0x80/0x80
 ? rcu_read_lock_bh_held+0x60/0xb0
 tcp_write_xmit+0x3f1/0x24d0
iwlwifi 0000:06:00.0: 0x034E001C | hcmd
 ? __check_object_size+0x180/0x350
iwlwifi 0000:06:00.0: 0x24020000 | isr0
 tcp_sendmsg_locked+0x8a9/0x1520
iwlwifi 0000:06:00.0: 0x01400000 | isr1
 ? tcp_sendpage+0x50/0x50
iwlwifi 0000:06:00.0: 0x48F0000A | isr2
 ? lock_release+0xb9/0x400
 ? tcp_sendmsg+0x14/0x40
iwlwifi 0000:06:00.0: 0x00C3080C | isr3
 ? lock_downgrade+0x390/0x390
 ? do_raw_spin_lock+0x114/0x1d0
iwlwifi 0000:06:00.0: 0x00200000 | isr4
 ? rwlock_bug.part.2+0x50/0x50
iwlwifi 0000:06:00.0: 0x034A001C | last cmd Id
 ? rwlock_bug.part.2+0x50/0x50
 ? lockdep_hardirqs_on_prepare+0xe/0x200
iwlwifi 0000:06:00.0: 0x0000C2F0 | wait_event
 ? __local_bh_enable_ip+0x87/0xe0
 ? inet_send_prepare+0x220/0x220
iwlwifi 0000:06:00.0: 0x000000C4 | l2p_control
 tcp_sendmsg+0x22/0x40
 sock_sendmsg+0x5f/0x70
iwlwifi 0000:06:00.0: 0x00010034 | l2p_duration
 __sys_sendto+0x19d/0x250
iwlwifi 0000:06:00.0: 0x00000007 | l2p_mhvalid
 ? __ia32_sys_getpeername+0x40/0x40
iwlwifi 0000:06:00.0: 0x00000000 | l2p_addr_match
 ? rcu_read_lock_held_common+0x12/0x50
 ? rcu_read_lock_sched_held+0x5a/0xd0
 ? rcu_read_lock_bh_held+0xb0/0xb0
 ? rcu_read_lock_sched_held+0x5a/0xd0
 ? rcu_read_lock_sched_held+0x5a/0xd0
 ? lock_release+0xb9/0x400
 ? lock_downgrade+0x390/0x390
 ? ktime_get+0x64/0x130
 ? ktime_get+0x8d/0x130
 ? rcu_read_lock_held_common+0x12/0x50
 ? rcu_read_lock_sched_held+0x5a/0xd0
 ? rcu_read_lock_held_common+0x12/0x50
 ? rcu_read_lock_sched_held+0x5a/0xd0
 ? rcu_read_lock_bh_held+0xb0/0xb0
 ? rcu_read_lock_bh_held+0xb0/0xb0
 __x64_sys_sendto+0x6f/0x80
 do_syscall_64+0x34/0xb0
 entry_SYSCALL_64_after_hwframe+0x46/0xb0
RIP: 0033:0x7f1d126e4531
Code: 00 00 00 00 0f 1f 44 00 00 f3 0f 1e fa 48 8d 05 35 80 0c 00 41 89 ca 8b 00 85 c0 75 1c 45 31 c9 45 31 c0 b8 2c 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 67 c3 66 0f 1f 44 00 00 55 48 83 ec 20 48 89
RSP: 002b:00007ffe21a679d8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 000000000000ffdc RCX: 00007f1d126e4531
RDX: 0000000000010000 RSI: 000000000374acf0 RDI: 0000000000000014
RBP: 00007ffe21a67ac0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R
---truncated---

Statement: Impact: Double-free in iwlwifi mvm TX error path (TSO) can lead to use-after-free and kernel crash. Privilege escalation cannot be ruled out. Affected only when the Intel iwlwifi/mvm driver is in use (e.g., AX210) and only by local user who sends traffic using WiFi.
An unprivileged user can trigger by sending traffic over the affected Wi-Fi interface.
Reliable exploitation is non-trivial since it relies on a rare error path.
Fixed in Red Hat Enterprise Linux 8 and in 9 starting from 9.3.

Mitigation: Update to a kernel including the fix. As a temporary mitigation, avoid using the affected adapter/driver; reducing large-segment TX (TSO/GSO) may lower likelihood, but wireless often doesn’t expose these offloads.

Remediation:
To mitigate this issue, prevent module iwlwifi from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.