{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2025-38255",
  "modified": "2026-10-07T17:22:01Z",
  "upstream": [
    "CVE-2025-38255"
  ],
  "published": "2025-07-09T10:43:51Z",
  "summary": "lib/group_cpus: fix NULL pointer dereference from group_cpus_evenly()",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nlib/group_cpus: fix NULL pointer dereference from group_cpus_evenly()\n\nWhile testing null_blk with configfs, echo 0 > poll_queues will trigger\nfollowing panic:\n\nBUG: kernel NULL pointer dereference, address: 0000000000000010\nOops: Oops: 0000 [#1] SMP NOPTI\nCPU: 27 UID: 0 PID: 920 Comm: bash Not tainted 6.15.0-02023-gadbdb95c8696-dirty #1238 PREEMPT(undef)\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014\nRIP: 0010:__bitmap_or+0x48/0x70\nCall Trace:\n <TASK>\n __group_cpus_evenly+0x822/0x8c0\n group_cpus_evenly+0x2d9/0x490\n blk_mq_map_queues+0x1e/0x110\n null_map_queues+0xc9/0x170 [null_blk]\n blk_mq_update_queue_map+0xdb/0x160\n blk_mq_update_nr_hw_queues+0x22b/0x560\n nullb_update_nr_hw_queues+0x71/0xf0 [null_blk]\n nullb_device_poll_queues_store+0xa4/0x130 [null_blk]\n configfs_write_iter+0x109/0x1d0\n vfs_write+0x26e/0x6f0\n ksys_write+0x79/0x180\n __x64_sys_write+0x1d/0x30\n x64_sys_call+0x45c4/0x45f0\n do_syscall_64+0xa5/0x240\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nRoot cause is that numgrps is set to 0, and ZERO_SIZE_PTR is returned from\nkcalloc(), and later ZERO_SIZE_PTR will be deferenced.\n\nFix the problem by checking numgrps first in group_cpus_evenly(), and\nreturn NULL directly if numgrps is zero.\n\n[yukuai3@huawei.com: also fix the non-SMP version]",
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            "linux_commit": "8f77e03530f65209a377d25023e912b288e039cd",
            "upstream_version": "6.12.34",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.12.36"
          }
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    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-38255"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/64a99eff8dcf1f951a544e6058341b2b19a8fdbd"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/29d39e0d5f16c060e32542b2cf351c09fd22b250"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/911ef2e8a7de5b2bae8ff11fb0bd01f699e6db65"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/df831e97739405ecbaddb85516bc7d4d1c933d6b"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-05-12T04:54:46Z"
  }
}