In the Linux kernel, the following vulnerability has been resolved:
perf/x86/intel/uncore: Fix die ID init and look up bugs
In snbep_pci2phy_map_init(), in the nr_node_ids > 8 path,
uncore_device_to_die() may return -1 when all CPUs associated
with the UBOX device are offline.
Remove the WARN_ON_ONCE(die_id == -1) check for two reasons:
-
The current code breaks out of the loop. This is incorrect because
pci_get_device() does not guarantee iteration in domain or bus order,
so additional UBOX devices may be skipped during the scan.
-
Returning -EINVAL is incorrect, since marking offline buses with
die_id == -1 is expected and should not be treated as an error.
Separately, when NUMA is disabled on a NUMA-capable platform,
pcibus_to_node() returns NUMA_NO_NODE, causing uncore_device_to_die()
to return -1 for all PCI devices. As a result,
spr_update_device_location(), used on Intel SPR and EMR, ignores the
corresponding PMON units and does not add them to the RB tree.
Fix this by using uncore_pcibus_to_dieid(), which retrieves topology
from the UBOX GIDNIDMAP register and works regardless of whether NUMA
is enabled in Linux. This requires snbep_pci2phy_map_init() to be
added in spr_uncore_pci_init().
Keep uncore_device_to_die() only for the nr_node_ids > 8 case, where
NUMA is expected to be enabled.