CVE-2024-46847: mm: vmalloc: ensure vmap_block is initialised before adding to queue

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-09-27 · updated 2026-08-04
Weakness: CWE-129

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.

Affected products

Linux kernel: from 6.6.37 before 6.6.51; from 6.9.8 before 6.10; from 6.10 before 6.10.10; 6.11-rc1, 6.11-rc2, 6.11-rc3, 6.11-rc4, 6.11-rc5, 6.11-rc6 — fixed in 6.10, 6.10.10, 6.6.51

How to fix

Upgrade to a fixed version: Linux kernel 6.10, 6.10.10, 6.6.51. Check the vendor advisory for mitigations.

References

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