CVE-2025-38255None▾ Sunlit

lib/group_cpus: fix NULL pointer dereference from group_cpus_evenly()

In the Linux kernel, the following vulnerability has been resolved: lib/group_cpus: fix NULL pointer dereference from group_cpus_evenly() While testing null_blk with configfs, echo 0 > poll_queues will trigger following panic: BUG: ke…

▾ Sunlit zone — Low / medium · no exploitation signal

Depth score3/ 100 · Minimal

impact 2.8 · likelihood 0 · exploitation 0

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Proof of concept

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Published

Jul 9, 2025

Updated

Nov 5, 2026

CVSS

—

Vendor

Linux

Product

Linux

CWE

—

Depth score

3 · Minimal

EPSS

0.17% · p6

Platforms

—

Source

CVEORG

Vector

—

CISA SSVC

decided 2026-11-05

Exploitation: none
Automatable: no
Technical impact: partial

Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake.

EPSS history

Exploit-prediction probability, daily snapshots since Nov 5.

0.2% → 0.2%

Timeline

Disclosure to exploitation, from the record and what we observed since indexing it.

3 events · 484 days

Jul 9, 2025Published
Disclosed via CVEORG
Nov 5, 2026Record revised
Last analysed / modified upstream
Nov 5, 2026EPSS first tracked
0.2%

Linux #cve.org

Affected

Linux >= 6a6dcae8f486c3f3298d0767d34505121c7b0b81 < 64a99eff8dcf1f951a544e6058341b2b19a8fdbd
Linux >= 6a6dcae8f486c3f3298d0767d34505121c7b0b81 < 29d39e0d5f16c060e32542b2cf351c09fd22b250
Linux >= 6a6dcae8f486c3f3298d0767d34505121c7b0b81 < 911ef2e8a7de5b2bae8ff11fb0bd01f699e6db65
Linux >= 6a6dcae8f486c3f3298d0767d34505121c7b0b81 < df831e97739405ecbaddb85516bc7d4d1c933d6b
Linux 6.3

Full technical detail▾

Overview

In the Linux kernel, the following vulnerability has been resolved:

lib/group_cpus: fix NULL pointer dereference from group_cpus_evenly()

While testing null_blk with configfs, echo 0 > poll_queues will trigger following panic:

BUG: kernel NULL pointer dereference, address: 0000000000000010 Oops: Oops: 0000 [#1] SMP NOPTI CPU: 27 UID: 0 PID: 920 Comm: bash Not tainted 6.15.0-02023-gadbdb95c8696-dirty #1238 PREEMPT(undef) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 RIP: 0010:__bitmap_or+0x48/0x70 Call Trace: <TASK> __group_cpus_evenly+0x822/0x8c0 group_cpus_evenly+0x2d9/0x490 blk_mq_map_queues+0x1e/0x110 null_map_queues+0xc9/0x170 [null_blk] blk_mq_update_queue_map+0xdb/0x160 blk_mq_update_nr_hw_queues+0x22b/0x560 nullb_update_nr_hw_queues+0x71/0xf0 [null_blk] nullb_device_poll_queues_store+0xa4/0x130 [null_blk] configfs_write_iter+0x109/0x1d0 vfs_write+0x26e/0x6f0 ksys_write+0x79/0x180 __x64_sys_write+0x1d/0x30 x64_sys_call+0x45c4/0x45f0 do_syscall_64+0xa5/0x240 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Root cause is that numgrps is set to 0, and ZERO_SIZE_PTR is returned from kcalloc(), and later ZERO_SIZE_PTR will be deferenced.

Fix the problem by checking numgrps first in group_cpus_evenly(), and return NULL directly if numgrps is zero.

[[email protected]: also fix the non-SMP version]

Affected

Linux >= 6a6dcae8f486c3f3298d0767d34505121c7b0b81 < 64a99eff8dcf1f951a544e6058341b2b19a8fdbd
Linux >= 6a6dcae8f486c3f3298d0767d34505121c7b0b81 < 29d39e0d5f16c060e32542b2cf351c09fd22b250
Linux >= 6a6dcae8f486c3f3298d0767d34505121c7b0b81 < 911ef2e8a7de5b2bae8ff11fb0bd01f699e6db65
Linux >= 6a6dcae8f486c3f3298d0767d34505121c7b0b81 < df831e97739405ecbaddb85516bc7d4d1c933d6b
Linux 6.3

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

References

Related vulnerabilities

Connected by shared product, vendor, weakness, or advisory.

#cve.org

lib/group_cpus: fix NULL pointer dereference from group_cpus_evenly()

▾ Sunlit zone — Low / medium · no exploitation signal

Depth score3/ 100 · Minimal

impact 2.8 · likelihood 0 · exploitation 0

Overview

In the Linux kernel, the following vulnerability has been resolved:

lib/group_cpus: fix NULL pointer dereference from group_cpus_evenly()

While testing null_blk with configfs, echo 0 > poll_queues will trigger following panic:

Root cause is that numgrps is set to 0, and ZERO_SIZE_PTR is returned from kcalloc(), and later ZERO_SIZE_PTR will be deferenced.

Fix the problem by checking numgrps first in group_cpus_evenly(), and return NULL directly if numgrps is zero.

[[email protected]: also fix the non-SMP version]

Affected

Linux >= 6a6dcae8f486c3f3298d0767d34505121c7b0b81 < 64a99eff8dcf1f951a544e6058341b2b19a8fdbd

Linux >= 6a6dcae8f486c3f3298d0767d34505121c7b0b81 < 29d39e0d5f16c060e32542b2cf351c09fd22b250

Linux >= 6a6dcae8f486c3f3298d0767d34505121c7b0b81 < 911ef2e8a7de5b2bae8ff11fb0bd01f699e6db65

Linux >= 6a6dcae8f486c3f3298d0767d34505121c7b0b81 < df831e97739405ecbaddb85516bc7d4d1c933d6b

Linux 6.3