In the Linux kernel, the following vulnerability has been resolved:
x86/amd_node: Avoid divide by zero on virtualized systems
On a virtualized system, the number of nodes does not have a relationship to the number of roots. A Xen PVH dom0 can calculate roots_per_node as 0, which crashes with a divide by zero in:
if (count++ % roots_per_node)
because the underlying topology code on Xen ends up making num_nodes 2 and num_roots 1 and the integer division result is 0.
The issue is seen with Xen, but it could affect other systems.
Set roots_per_node to 1 in this case. Print a firmware bug when this is performed for non-virtualized systems.
[ bp: Massage commit message. ]
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