Linux Kernel up to 5.16.15 MIPS kernel/sched/core.c sched_core_cpu_starting privilege escalation

CVSS Meta Temp Score
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CTI Interest Score
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5.4$0-$5k0.00

Summaryinfo

A vulnerability was found in Linux Kernel up to 5.16.15. It has been classified as problematic. Affected by this issue is the function sched_core_cpu_starting of the file kernel/sched/core.c of the component MIPS. This manipulation causes an unknown weakness. This vulnerability is handled as CVE-2022-48845. There is not any exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Linux Kernel up to 5.16.15. It has been declared as problematic. Affected by this vulnerability is the function sched_core_cpu_starting of the file kernel/sched/core.c of the component MIPS. The impact remains unknown. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: MIPS: smp: fill in sibling and core maps earlier After enabling CONFIG_SCHED_CORE (landed during 5.14 cycle), 2-core 2-thread-per-core interAptiv (CPS-driven) started emitting the following: [ 0.025698] CPU1 revision is: 0001a120 (MIPS interAptiv (multi)) [ 0.048183] ------------[ cut here ]------------ [ 0.048187] WARNING: CPU: 1 PID: 0 at kernel/sched/core.c:6025 sched_core_cpu_starting+0x198/0x240 [ 0.048220] Modules linked in: [ 0.048233] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.17.0-rc3+ #35 b7b319f24073fd9a3c2aa7ad15fb7993eec0b26f [ 0.048247] Stack : 817f0000 00000004 327804c8 810eb050 00000000 00000004 00000000 c314fdd1 [ 0.048278] 830cbd64 819c0000 81800000 817f0000 83070bf4 00000001 830cbd08 00000000 [ 0.048307] 00000000 00000000 815fcbc4 00000000 00000000 00000000 00000000 00000000 [ 0.048334] 00000000 00000000 00000000 00000000 817f0000 00000000 00000000 817f6f34 [ 0.048361] 817f0000 818a3c00 817f0000 00000004 00000000 00000000 4dc33260 0018c933 [ 0.048389] ... [ 0.048396] Call Trace: [ 0.048399] [] show_stack+0x3c/0x140 [ 0.048424] [] dump_stack_lvl+0x60/0x80 [ 0.048440] [] __warn+0xc0/0xf4 [ 0.048454] [] warn_slowpath_fmt+0x64/0x10c [ 0.048467] [] sched_core_cpu_starting+0x198/0x240 [ 0.048483] [] sched_cpu_starting+0x14/0x80 [ 0.048497] [] cpuhp_invoke_callback_range+0x78/0x140 [ 0.048510] [] notify_cpu_starting+0x94/0x140 [ 0.048523] [] start_secondary+0xbc/0x280 [ 0.048539] [ 0.048543] ---[ end trace 0000000000000000 ]--- [ 0.048636] Synchronize counters for CPU 1: done. ...for each but CPU 0/boot. Basic debug printks right before the mentioned line say: [ 0.048170] CPU: 1, smt_mask: So smt_mask, which is sibling mask obviously, is empty when entering the function. This is critical, as sched_core_cpu_starting() calculates core-scheduling parameters only once per CPU start, and it's crucial to have all the parameters filled in at that moment (at least it uses cpu_smt_mask() which in fact is `&cpu_sibling_map[cpu]` on MIPS). A bit of debugging led me to that set_cpu_sibling_map() performing the actual map calculation, was being invocated after notify_cpu_start(), and exactly the latter function starts CPU HP callback round (sched_core_cpu_starting() is basically a CPU HP callback). While the flow is same on ARM64 (maps after the notifier, although before calling set_cpu_online()), x86 started calculating sibling maps earlier than starting the CPU HP callbacks in Linux 4.14 (see [0] for the reference). Neither me nor my brief tests couldn't find any potential caveats in calculating the maps right after performing delay calibration, but the WARN splat is now gone. The very same debug prints now yield exactly what I expected from them: [ 0.048433] CPU: 1, smt_mask: 0-1 [0] https://git.kernel.org/pub/scm/linux/kernel/git/mips/linux.git/commit/?id=76ce7cfe35ef

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2022-48845 since 07/16/2024. The exploitation appears to be easy. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 247015 (Linux Distros Unpatched Vulnerability : CVE-2022-48845), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 4.9.308, 4.14.273, 4.19.236, 5.4.186, 5.10.107, 5.15.30 or 5.16.16 eliminates this vulnerability. Applying the patch 7315f8538db0/32813321f18d/56eaacb8137b/c2420bc33331/e8ad9ecc4069/be538b764a46/94647aec80d0/f2703def339c is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (247015). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.5
VulDB Meta Temp Score: 5.4

VulDB Base Score: 5.5
VulDB Temp Score: 5.3
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 5.5
NVD Vector: 🔍

CVSSv2info

AVACAuCIA
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VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

Exploitinginfo

Class: Privilege escalation
CWE: Unknown
CAPEC: 🔍
ATT&CK: 🔍

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

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Nessus ID: 247015
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2022-48845

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔍

Upgrade: Kernel 4.9.308/4.14.273/4.19.236/5.4.186/5.10.107/5.15.30/5.16.16
Patch: 7315f8538db0/32813321f18d/56eaacb8137b/c2420bc33331/e8ad9ecc4069/be538b764a46/94647aec80d0/f2703def339c

Timelineinfo

07/16/2024 🔍
07/16/2024 +0 days 🔍
07/16/2024 +0 days 🔍
08/10/2025 +390 days 🔍

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2022-48845 (🔍)
GCVE (CVE): GCVE-0-2022-48845
GCVE (VulDB): GCVE-100-271591

Entryinfo

Created: 07/16/2024 16:51
Updated: 08/10/2025 03:13
Changes: 07/16/2024 16:51 (58), 07/25/2024 03:04 (11), 08/10/2025 03:13 (2)
Complete: 🔍
Cache ID: 216::103

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