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

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

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
• https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html
• https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html