CVE-2024-46847: mm: vmalloc: ensure vmap_block is initialised before adding to queue
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.
Classification
CVE ID: CVE-2024-46847
CVSS Base Severity: MEDIUM
CVSS Base Score: 5.5
CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Affected Products
Vendor: Linux
Product: Linux
Exploit Prediction Scoring System (EPSS)
EPSS Score: 0.03% (probability of being exploited)
EPSS Percentile: 7.43% (scored less or equal to compared to others)
EPSS Date: 2025-06-02 (when was this score calculated)
Stakeholder-Specific Vulnerability Categorization (SSVC)
SSVC Exploitation: none
SSVC Technical Impact: partial
SSVC Automatable: false
References
https://nvd.nist.gov/vuln/detail/CVE-2024-46847https://git.kernel.org/stable/c/1b2770e27d6d952f491bb362b657e5b2713c3efd
https://git.kernel.org/stable/c/6cf74e0e5e3ab5d5c9defb4c73dad54d52224671
https://git.kernel.org/stable/c/3e3de7947c751509027d26b679ecd243bc9db255