CVE-2024-40917 — memblock: make memblock_set_node() also warn about use of MAX_NUMNODES

Affected: Linux

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

memblock: make memblock_set_node() also warn about use of MAX_NUMNODES

On an (old) x86 system with SRAT just covering space above 4Gb:

ACPI: SRAT: Node 0 PXM 0 [mem 0x100000000-0xfffffffff] hotplug

the commit referenced below leads to this NUMA configuration no longer being refused by a CONFIG_NUMA=y kernel (previously

NUMA: nodes only cover 6144MB of your 8185MB e820 RAM. Not used. No NUMA configuration found Faking a node at [mem 0x0000000000000000-0x000000027fffffff]

was seen in the log directly after the message quoted above), because of memblock_validate_numa_coverage() checking for NUMA_NO_NODE (only). This in turn led to memblock_alloc_range_nid()'s warning about MAX_NUMNODES triggering, followed by a NULL deref in memmap_init() when trying to access node 64's (NODE_SHIFT=6) node data.

To compensate said change, make memblock_set_node() warn on and adjust a passed in value of MAX_NUMNODES, just like various other functions already do.

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CVE-2024-40917 — memblock: make memblock_set_node() also warn about use of MAX_NUMNODES