CVE-2024-46847 mm: vmalloc: ensure vmap_block is initialised before adding to queue
A race condition in the Linux kernel's vmalloc subsystem allows out-of-bounds access, potentially causing a system crash or denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-46847?
CVE-2024-46847 is a high-severity vulnerability in Linux kernel, published on 27 Sep 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
mm: vmalloc: ensure vmap_block is initialised before adding to queue
Commit 8c61291fd850 ("mm: fix incorrect vbq reference in purge_fragmented_block") extended the 'vmap_block' structure to contain a 'cpu' field which is set at allocation time to the id of the initialising CPU.
When a new 'vmap_block' is being instantiated by new_vmap_block(), the partially initialised structure is added to the local 'vmap_block_queue' xarray before the 'cpu' field has been initialised. If another CPU is concurrently walking the xarray (e.g. via vm_unmap_aliases()), then it may perform an out-of-bounds access to the remote queue thanks to an uninitialised index.
This has been observed as UBSAN errors in Android:
| Internal error: UBSAN: array index out of bounds: 00000000f2005512 [#1] PREEMPT SMP | | Call trace: | purge_fragmented_block+0x204/0x21c | _vm_unmap_aliases+0x170/0x378 | vm_unmap_aliases+0x1c/0x28 | change_memory_common+0x1dc/0x26c | set_memory_ro+0x18/0x24 | module_enable_ro+0x98/0x238 | do_init_module+0x1b0/0x310
Move the initialisation of 'vb->cpu' in new_vmap_block() ahead of the addition to the xarray.
Weakness: CWE-129
Which versions are affected by CVE-2024-46847?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2024-46847?
Apply the vendor's patch.
Is CVE-2024-46847 being exploited?
There is no known exploitation of CVE-2024-46847 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2024-46847, DEBIAN-CVE-2024-46847, GHSA-9r77-32hh-rxf4, UBUNTU-CVE-2024-46847.