cacheinfo: Allocate memory during CPU hotplug if not done from the primary CPU
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: no
- Technical impact: partial
Summary
In the Linux kernel, the following vulnerability has been resolved: cacheinfo: Allocate memory during CPU hotplug if not done from the primary CPU Commit 5944ce092b97 ("arch_topology: Build cacheinfo from primary CPU") adds functionality that architectures can use to optionally allocate and build cacheinfo early during boot. Commit 6539cffa9495 ("cacheinfo: Add arch specific early level initializer") lets secondary CPUs correct (and reallocate memory) cacheinfo data if needed. If the early build functionality is not used and cacheinfo does not need correction, memory for cacheinfo is never allocated. x86 does not use the early build functionality. Consequently, during the cacheinfo CPU hotplug callback, last_level_cache_is_valid() attempts to dereference a NULL pointer: BUG: kernel NULL pointer dereference, address: 0000000000000100 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not present page PGD 0 P4D 0 Oops: 0000 [#1] PREEPMT SMP NOPTI CPU: 0 PID 19 Comm: cpuhp/0 Not tainted 6.4.0-rc2 #1 RIP: 0010: last_level_cache_is_valid+0x95/0xe0a Allocate memory for cacheinfo during the cacheinfo CPU hotplug callback if not done earlier. Moreover, 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. While here, remove an unnecessary indentation in allocate_cache_info(). [ bp: Massage. ]
Timeline
- CVE published
- CISA SSVC assessment
Exploitation: none · Automatable: no · Technical impact: partial
- Record last updated
Affected versions
- Linux Linux
Version range not reported
- Linux Linux
6.4