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Linux KernelOperating system · Linux

CVE-2022-48845

MEDIUM · 5.5 CVSS v3.1 Published 2024-07-16
Fix available
A fix is available. Upgrade to 4.9.308 / 4.14.273 or later.
See remediation →
57/100
Remediation priority · Elevated
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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] [<8105a7bc>] show_stack+0x3c/0x140 [ 0.048424] [<8131c2a0>] dump_stack_lvl+0x60/0x80 [ 0.048440] [<8108b5c0>] __warn+0xc0/0xf4 [ 0.048454] [<8108b658>] warn_slowpath_fmt+0x64/0x10c [ 0.048467] [<810bd418>] sched_core_cpu_starting+0x198/0x240 [ 0.048483] [<810c6514>] sched_cpu_starting+0x14/0x80 [ 0.048497] [<8108c0f8>] cpuhp_invoke_callback_range+0x78/0x140 [ 0.048510] [<8108d914>] notify_cpu_starting+0x94/0x140 [ 0.048523] [<8106593c>] 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

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis

A detailed technical summary for this CVE is being prepared.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:< 4.9.308>= 4.10, < 4.14.273>= 4.15, < 4.19.236>= 4.20, < 5.4.186>= 5.5, < 5.10.107>= 5.11, < 5.15.30>= 5.16, < 5.16.16

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 4.9.308 / 4.14.273 / 4.19.236 or later
Fixed in 4.9.3084.14.2734.19.236
Vendor patch git.kernel.org →
Recommended fix High confidence

Linux kernel >= 5.4.186 (specific stable versions include 5.4.186+, 5.10.103+, 5.15.21+, or 5.17+ where the patch was backported)

  1. Identify the current running Linux kernel version using `uname -r`
  2. Determine if the system uses MIPS architecture (this vulnerability specifically affects MIPS)
  3. Check if CONFIG_SCHED_CORE is enabled in the kernel configuration (required for the bug to manifest)
  4. Upgrade the Linux kernel to a version >= 5.4.186 which contains the fix for calculating sibling maps earlier in the boot process
Caveat This is a bug fix for MIPS SMP systems; no breaking changes expected for non-MIPS architectures. The fix simply reorders when sibling/core maps are populated relative to CPU hotplug callbacks.

Generated from the published advisory — verify against the referenced sources before acting.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

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