wifi: brcmfmac: Fix potential shift-out-of-bounds in brcmf_fw_alloc_request()
CVE: CVE-2022-50551
Component: kernel
CWE: CWE-682
Severity: Moderate
CVSS v3: 6.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/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: Fix potential shift-out-of-bounds in brcmf_fw_alloc_request()

This patch fixes a shift-out-of-bounds in brcmfmac that occurs in
BIT(chiprev) when a 'chiprev' provided by the device is too large.
It should also not be equal to or greater than BITS_PER_TYPE(u32)
as we do bitwise AND with a u32 variable and BIT(chiprev). The patch
adds a check that makes the function return NULL if that is the case.
Note that the NULL case is later handled by the bus-specific caller,
brcmf_usb_probe_cb() or brcmf_usb_reset_resume(), for example.

Found by a modified version of syzkaller.

UBSAN: shift-out-of-bounds in drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.c
shift exponent 151055786 is too large for 64-bit type 'long unsigned int'
CPU: 0 PID: 1885 Comm: kworker/0:2 Tainted: G           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
 ubsan_epilogue+0x5/0x40
 __ubsan_handle_shift_out_of_bounds.cold+0x53/0xdb
 ? lock_chain_count+0x20/0x20
 brcmf_fw_alloc_request.cold+0x19/0x3ea
 ? brcmf_fw_get_firmwares+0x250/0x250
 ? brcmf_usb_ioctl_resp_wait+0x1a7/0x1f0
 brcmf_usb_get_fwname+0x114/0x1a0
 ? brcmf_usb_reset_resume+0x120/0x120
 ? number+0x6c4/0x9a0
 brcmf_c_process_clm_blob+0x168/0x590
 ? put_dec+0x90/0x90
 ? enable_ptr_key_workfn+0x20/0x20
 ? brcmf_common_pd_remove+0x50/0x50
 ? rcu_read_lock_sched_held+0xa1/0xd0
 brcmf_c_preinit_dcmds+0x673/0xc40
 ? brcmf_c_set_joinpref_default+0x100/0x100
 ? rcu_read_lock_sched_held+0xa1/0xd0
 ? rcu_read_lock_bh_held+0xb0/0xb0
 ? lock_acquire+0x19d/0x4e0
 ? find_held_lock+0x2d/0x110
 ? brcmf_usb_deq+0x1cc/0x260
 ? mark_held_locks+0x9f/0xe0
 ? lockdep_hardirqs_on_prepare+0x273/0x3e0
 ? _raw_spin_unlock_irqrestore+0x47/0x50
 ? trace_hardirqs_on+0x1c/0x120
 ? brcmf_usb_deq+0x1a7/0x260
 ? brcmf_usb_rx_fill_all+0x5a/0xf0
 brcmf_attach+0x246/0xd40
 ? wiphy_new_nm+0x1476/0x1d50
 ? kmemdup+0x30/0x40
 brcmf_usb_probe+0x12de/0x1690
 ? brcmf_usbdev_qinit.constprop.0+0x470/0x470
 usb_probe_interface+0x25f/0x710
 really_probe+0x1be/0xa90
 __driver_probe_device+0x2ab/0x460
 ? usb_match_id.part.0+0x88/0xc0
 driver_probe_device+0x49/0x120
 __device_attach_driver+0x18a/0x250
 ? driver_allows_async_probing+0x120/0x120
 bus_for_each_drv+0x123/0x1a0
 ? bus_rescan_devices+0x20/0x20
 ? lockdep_hardirqs_on_prepare+0x273/0x3e0
 ? trace_hardirqs_on+0x1c/0x120
 __device_attach+0x207/0x330
 ? device_bind_driver+0xb0/0xb0
 ? kobject_uevent_env+0x230/0x12c0
 bus_probe_device+0x1a2/0x260
 device_add+0xa61/0x1ce0
 ? __mutex_unlock_slowpath+0xe7/0x660
 ? __fw_devlink_link_to_suppliers+0x550/0x550
 usb_set_configuration+0x984/0x1770
 ? kernfs_create_link+0x175/0x230
 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
 ? driver_allows_async_probing+0x120/0x120
 bus_for_each_drv+0x123/0x1a0
 ? bus_rescan_devices+0x20/0x20
 ? lockdep_hardirqs_on_prepare+0x273/0x3e0
 ? trace_hardirqs_on+0x1c/0x120
 __device_attach+0x207/0x330
 ? device_bind_driver+0xb0/0xb0
 ? kobject_uevent_env+0x230/0x12c0
 bus_probe_device+0x1a2/0x260
 device_add+0xa61/0x1ce0
 ? __fw_devlink_link_to_suppliers+0x550/0x550
 usb_new_device.cold+0x463/0xf66
 ? hub_disconnect+0x400/0x400
 ? _raw_spin_unlock_irq+0x24/0x30
 hub_event+0x10d5/0x3330
 ? hub_port_debounce+0x280/0x280
 ? __lock_acquire+0x1671/0x5790
 ? wq_calc_node_cpumask+0x170/0x2a0
 ? lock_release+0x640/0x640
 ? rcu_read_lock_sched_held+0xa1/0xd0
 ? rcu_read_lock_bh_held+0xb0/0xb0
 ? lockdep_hardirqs_on_prepare+0x273/0x3e0
 process_one_work+0x873/0x13e0
 ? lock_release+0x640/0x640
 ? pwq_dec_nr_in_flight+0x320/0x320
 ? rwlock_bug.part.0+0x90/0x90
 worker_thread+0x8b/0xd10
 ? __kthread_parkme+0xd9/0x1d0
 ? pr
---truncated---

Statement: The patch prevents a shift-out-of-bounds in brcmf_fw_map_chip_to_name() (BIT(chiprev)) when a device reports an out-of-range chiprev, which could otherwise lead to undefined behavior and kernel crashes during driver probe.
Impact is mostly DoS: it can be reproduced by attaching a malicious/buggy Broadcom USB/SDIO device (or USB emulator/gadget) that advertises an excessively large chiprev, triggering the UBSAN splat/panic during probe.
For the CVSS the PR:H — exploitation requires control of the hardware/firmware or the ability to emulate/hot-plug a crafted device (or load/probe the driver).

Remediation: