UBUNTU: SAUCE: cacheinfo: Check for null last-level cache info

BugLink: https://bugs.launchpad.net/bugs/2049793

Before determining the validity of the last-level cache info, ensure that
it has been allocated. Simply checking for non-zero cache_leaves() is not
sufficient, as some architectures (e.g., Intel processors) have non-zero
cache_leaves() before allocation.

Dereferencing NULL cacheinfo can occur in update_per_cpu_data_slice_size().
This function iterates over all online CPUs. However, a CPU may have come
online recently, but its cacheinfo may not have been allocated yet.

Cc: Andreas Herrmann <aherrmann@suse.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen Yu <yu.c.chen@intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Radu Rendec <rrendec@redhat.com>
Cc: Pierre Gondois <Pierre.Gondois@arm.com>
Cc: Pu Wen <puwen@hygon.cn>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: Will Deacon <will@kernel.org>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: stable@vger.kernel.org
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
(cherry-picked from https://lore.kernel.org/all/20231212222519.12834-2-ricardo.neri-calderon@linux.intel.com/raw)
Signed-off-by: You-Sheng Yang <vicamo.yang@canonical.com>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

drivers/base/cacheinfo.c

@@ -61,6 +61,9 @@ bool last_level_cache_is_valid(unsigned int cpu)
 	if (!cache_leaves(cpu))
 		return false;
 
+	if (!per_cpu_cacheinfo(cpu))
+		return false;
+
 	llc = per_cpu_cacheinfo_idx(cpu, cache_leaves(cpu) - 1);
 
 	return (llc->attributes & CACHE_ID) || !!llc->fw_token;