Linux vulnerability

What happened

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.

Affected versions

Linux: 9a7832ce3d920426a36cdd78eda4b3568d4d09e3 through before bdb35811ff41a1678620a407056b6372f350028a (git); 9a7832ce3d920426a36cdd78eda4b3568d4d09e3 through before c79ef3342632e71ac8612a2a1cc17ac84dd258b4 (git); 9a7832ce3d920426a36cdd78eda4b3568d4d09e3 through before 6a5dc3ee97581da2907fc7acd62853f07184de67 (git); 9a7832ce3d920426a36cdd78eda4b3568d4d09e3 through before a16d1ec4dd0cdcf689f324adde6067083bce9099 (git); 5.12 Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

• Apply vendor-provided updates or mitigations.
• Review affected product exposure and access logs.