Subject: CVE-2024-26895: wifi: wilc1000: prevent use-after-free on vif when cleaning up all interfaces

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

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

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

wifi: wilc1000: prevent use-after-free on vif when cleaning up all interfaces

wilc_netdev_cleanup currently triggers a KASAN warning, which can be
observed on interface registration error path, or simply by
removing the module/unbinding device from driver:

echo spi0.1 > /sys/bus/spi/drivers/wilc1000_spi/unbind

==================================================================
BUG: KASAN: slab-use-after-free in wilc_netdev_cleanup+0x508/0x5cc
Read of size 4 at addr c54d1ce8 by task sh/86

CPU: 0 PID: 86 Comm: sh Not tainted 6.8.0-rc1+ #117
Hardware name: Atmel SAMA5
 unwind_backtrace from show_stack+0x18/0x1c
 show_stack from dump_stack_lvl+0x34/0x58
 dump_stack_lvl from print_report+0x154/0x500
 print_report from kasan_report+0xac/0xd8
 kasan_report from wilc_netdev_cleanup+0x508/0x5cc
 wilc_netdev_cleanup from wilc_bus_remove+0xc8/0xec
 wilc_bus_remove from spi_remove+0x8c/0xac
 spi_remove from device_release_driver_internal+0x434/0x5f8
 device_release_driver_internal from unbind_store+0xbc/0x108
 unbind_store from kernfs_fop_write_iter+0x398/0x584
 kernfs_fop_write_iter from vfs_write+0x728/0xf88
 vfs_write from ksys_write+0x110/0x1e4
 ksys_write from ret_fast_syscall+0x0/0x1c

[...]

Allocated by task 1:
 kasan_save_track+0x30/0x5c
 __kasan_kmalloc+0x8c/0x94
 __kmalloc_node+0x1cc/0x3e4
 kvmalloc_node+0x48/0x180
 alloc_netdev_mqs+0x68/0x11dc
 alloc_etherdev_mqs+0x28/0x34
 wilc_netdev_ifc_init+0x34/0x8ec
 wilc_cfg80211_init+0x690/0x910
 wilc_bus_probe+0xe0/0x4a0
 spi_probe+0x158/0x1b0
 really_probe+0x270/0xdf4
 __driver_probe_device+0x1dc/0x580
 driver_probe_device+0x60/0x140
 __driver_attach+0x228/0x5d4
 bus_for_each_dev+0x13c/0x1a8
 bus_add_driver+0x2a0/0x608
 driver_register+0x24c/0x578
 do_one_initcall+0x180/0x310
 kernel_init_freeable+0x424/0x484
 kernel_init+0x20/0x148
 ret_from_fork+0x14/0x28

Freed by task 86:
 kasan_save_track+0x30/0x5c
 kasan_save_free_info+0x38/0x58
 __kasan_slab_free+0xe4/0x140
 kfree+0xb0/0x238
 device_release+0xc0/0x2a8
 kobject_put+0x1d4/0x46c
 netdev_run_todo+0x8fc/0x11d0
 wilc_netdev_cleanup+0x1e4/0x5cc
 wilc_bus_remove+0xc8/0xec
 spi_remove+0x8c/0xac
 device_release_driver_internal+0x434/0x5f8
 unbind_store+0xbc/0x108
 kernfs_fop_write_iter+0x398/0x584
 vfs_write+0x728/0xf88
 ksys_write+0x110/0x1e4
 ret_fast_syscall+0x0/0x1c
 [...]

David Mosberger-Tan initial investigation [1] showed that this
use-after-free is due to netdevice unregistration during vif list
traversal. When unregistering a net device, since the needs_free_netdev has
been set to true during registration, the netdevice object is also freed,
and as a consequence, the corresponding vif object too, since it is
attached to it as private netdevice data. The next occurrence of the loop
then tries to access freed vif pointer to the list to move forward in the
list.

Fix this use-after-free thanks to two mechanisms:
- navigate in the list with list_for_each_entry_safe, which allows to
  safely modify the list as we go through each element. For each element,
  remove it from the list with list_del_rcu
- make sure to wait for RCU grace period end after each vif removal to make
  sure it is safe to free the corresponding vif too (through
  unregister_netdev)

Since we are in a RCU "modifier" path (not a "reader" path), and because
such path is expected not to be concurrent to any other modifier (we are
using the vif_mutex lock), we do not need to use RCU list API, that's why
we can benefit from list_for_each_entry_safe.

[1] https://lore.kernel.org/linux-wireless/[email-masked]/

The Linux kernel CVE team has assigned CVE-2024-26895 to this issue.

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

	Issue introduced in 5.5 with commit 8399918f3056 and fixed in 5.10.214 with commit 5956f4203b6c
	Issue introduced in 5.5 with commit 8399918f3056 and fixed in 5.15.153 with commit fe20e3d56bc9
	Issue introduced in 5.5 with commit 8399918f3056 and fixed in 6.1.83 with commit a9545af2a533
	Issue introduced in 5.5 with commit 8399918f3056 and fixed in 6.6.23 with commit 3da9d32b7f4a
	Issue introduced in 5.5 with commit 8399918f3056 and fixed in 6.7.11 with commit 24228dcf1d30
	Issue introduced in 5.5 with commit 8399918f3056 and fixed in 6.8.2 with commit 73a2aa0aef86
	Issue introduced in 5.5 with commit 8399918f3056 and fixed in 6.9 with commit cb5942b77c05

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-2024-26895
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/microchip/wilc1000/netdev.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/5956f4203b6cdd0755bbdd21b45f3933c7026208
	https://git.kernel.org/stable/c/fe20e3d56bc911408fc3c27a17c59e9d7885f7d1
	https://git.kernel.org/stable/c/a9545af2a533739ffb64d6c9a6fec6f13e2b505f
	https://git.kernel.org/stable/c/3da9d32b7f4a1a9f7e4bb15bb82f2b2dd6719447
	https://git.kernel.org/stable/c/24228dcf1d30c2231caa332be7d3090ac59fbfe9
	https://git.kernel.org/stable/c/73a2aa0aef86c2c07be5a2f42c9e6047e1a2f7bb
	https://git.kernel.org/stable/c/cb5942b77c05d54310a0420cac12935e9b6aa21c