CVE-2024-50150

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

usb: typec: altmode should keep reference to parent

The altmode device release refers to its parent device, but without keeping a reference to it.

When registering the altmode, get a reference to the parent and put it in the release function.

Before this fix, when using CONFIG_DEBUG_KOBJECT_RELEASE, we see issues like this:

[ 43.572860] kobject: port0.0 (ffff8880057ba008): kobject_release, parent 0000000000000000 (delayed 3000) [ 43.573532] kobject: port0.1 (ffff8880057bd008): kobject_release, parent 0000000000000000 (delayed 1000) [ 43.574407] kobject: port0 (ffff8880057b9008): kobject_release, parent 0000000000000000 (delayed 3000) [ 43.575059] kobject: port1.0 (ffff8880057ca008): kobject_release, parent 0000000000000000 (delayed 4000) [ 43.575908] kobject: port1.1 (ffff8880057c9008): kobject_release, parent 0000000000000000 (delayed 4000) [ 43.576908] kobject: typec (ffff8880062dbc00): kobject_release, parent 0000000000000000 (delayed 4000) [ 43.577769] kobject: port1 (ffff8880057bf008): kobject_release, parent 0000000000000000 (delayed 3000) [ 46.612867] ================================================================== [ 46.613402] BUG: KASAN: slab-use-after-free in typec_altmode_release+0x38/0x129 [ 46.614003] Read of size 8 at addr ffff8880057b9118 by task kworker/2:1/48 [ 46.614538] [ 46.614668] CPU: 2 UID: 0 PID: 48 Comm: kworker/2:1 Not tainted 6.12.0-rc1-00138-gedbae730ad31 #535 [ 46.615391] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014 [ 46.616042] Workqueue: events kobject_delayed_cleanup [ 46.616446] Call Trace: [ 46.616648] [ 46.616820] dump_stack_lvl+0x5b/0x7c [ 46.617112] ? typec_altmode_release+0x38/0x129 [ 46.617470] print_report+0x14c/0x49e [ 46.617769] ? rcu_read_unlock_sched+0x56/0x69 [ 46.618117] ? __virt_addr_valid+0x19a/0x1ab [ 46.618456] ? kmem_cache_debug_flags+0xc/0x1d [ 46.618807] ? typec_altmode_release+0x38/0x129 [ 46.619161] kasan_report+0x8d/0xb4 [ 46.619447] ? typec_altmode_release+0x38/0x129 [ 46.619809] ? process_scheduled_works+0x3cb/0x85f [ 46.620185] typec_altmode_release+0x38/0x129 [ 46.620537] ? process_scheduled_works+0x3cb/0x85f [ 46.620907] device_release+0xaf/0xf2 [ 46.621206] kobject_delayed_cleanup+0x13b/0x17a [ 46.621584] process_scheduled_works+0x4f6/0x85f [ 46.621955] ? __pfx_process_scheduled_works+0x10/0x10 [ 46.622353] ? hlock_class+0x31/0x9a [ 46.622647] ? lock_acquired+0x361/0x3c3 [ 46.622956] ? move_linked_works+0x46/0x7d [ 46.623277] worker_thread+0x1ce/0x291 [ 46.623582] ? __kthread_parkme+0xc8/0xdf [ 46.623900] ? __pfx_worker_thread+0x10/0x10 [ 46.624236] kthread+0x17e/0x190 [ 46.624501] ? kthread+0xfb/0x190 [ 46.624756] ? __pfx_kthread+0x10/0x10 [ 46.625015] ret_from_fork+0x20/0x40 [ 46.625268] ? __pfx_kthread+0x10/0x10 [ 46.625532] ret_from_fork_asm+0x1a/0x30 [ 46.625805] [ 46.625953] [ 46.626056] Allocated by task 678: [ 46.626287] kasan_save_stack+0x24/0x44 [ 46.626555] kasan_save_track+0x14/0x2d [ 46.626811] __kasan_kmalloc+0x3f/0x4d [ 46.627049] __kmalloc_noprof+0x1bf/0x1f0 [ 46.627362] typec_register_port+0x23/0x491 [ 46.627698] cros_typec_probe+0x634/0xbb6 [ 46.628026] platform_probe+0x47/0x8c [ 46.628311] really_probe+0x20a/0x47d [ 46.628605] device_driver_attach+0x39/0x72 [ 46.628940] bind_store+0x87/0xd7 [ 46.629213] kernfs_fop_write_iter+0x1aa/0x218 [ 46.629574] vfs_write+0x1d6/0x29b [ 46.629856] ksys_write+0xcd/0x13b [ 46.630128] do_syscall_64+0xd4/0x139 [ 46.630420] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 46.630820] [ 46.630946] Freed by task 48: [ 46.631182] kasan_save_stack+0x24/0x44 [ 46.631493] kasan_save_track+0x14/0x2d [ 46.631799] kasan_save_free_info+0x3f/0x4d [ 46.632144] __kasan_slab_free+0x37/0x45 [ 46.632474] —truncated—

Weakness

Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.

Affected Software

Extended Description

The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:

In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.

Potential Mitigations

References

• https://git.kernel.org/stable/c/1ded6b12499e6dee9b0e1ceac633be36538f6fc2
• https://git.kernel.org/stable/c/2b0b33e8a58388fa9078f0fbe9af1900e6b08879
• https://git.kernel.org/stable/c/2c15c4133d00f5da632fce60ed013fc31aa9aa58
• https://git.kernel.org/stable/c/68a7c7fe322546be1464174c8d85874b8161deda
• https://git.kernel.org/stable/c/6af43ec3bf40f8b428d9134ffa7a291aecd60da8
• https://git.kernel.org/stable/c/87474406056891e4fdea0794e1f632b21b3dfa27
• https://git.kernel.org/stable/c/bee1b68cb8bcee4fd3a8bde3a4886e0b1375dc4d
• https://git.kernel.org/stable/c/befab3a278c59db0cc88c8799638064f6d3fd6f8