tty: xilinx_uartps: split sysrq handling

{
  "id": "d16d87336d3957f6f6af89c8be20a8bb8017af44aa1d6547078b81da530402f5",
  "url": "https://osv.dev/vulnerability/CVE-2025-21820",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "tty: xilinx_uartps: split sysrq handling",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: tty: xilinx_uartps: split sysrq handling lockdep detects the following circular locking dependency: CPU 0 CPU 1 ========================== ============================ cdns_uart_isr() printk() uart_port_lock(port) console_lock() cdns_uart_console_write() if (!port->sysrq) uart_port_lock(port) uart_handle_break() port->sysrq = ... uart_handle_sysrq_char() printk() console_lock() The fixed commit attempts to avoid this situation by only taking the port lock in cdns_uart_console_write if port->sysrq unset. However, if (as shown above) cdns_uart_console_write runs before port->sysrq is set, then it will try to take the port lock anyway. This may result in a deadlock. Fix this by splitting sysrq handling into two parts. We use the prepare helper under the port lock and defer handling until we release the lock.",
    "evidence": "osv:CVE-2025-21820",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
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            "value": "5.15.179",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.129",
            "evidence": "/affected/1/ranges"
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          {
            "value": "6.6.78",
            "evidence": "/affected/1/ranges"
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          {
            "value": "6.12.14",
            "evidence": "/affected/1/ranges"
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          {
            "value": "6.13.3",
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    "severity": "unknown",
    "structured": {
      "id": "CVE-2025-21820",
      "aliases": [
        "CVE-2025-21820"
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                  "fixed": "4410dba9807a17a93f649a9f5870ceaf30a675a3"
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            "ecosystem": "Linux"
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      "modified": "2026-10-28T02:30:32.853172651Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/4410dba9807a17a93f649a9f5870ceaf30a675a3",
        "https://git.kernel.org/stable/c/8ea0e7b3d7b8f2f0fc9db491ff22a0abe120801c",
        "https://git.kernel.org/stable/c/9b88a7c4584ba67267a051069b8abe44fc9595b2",
        "https://git.kernel.org/stable/c/b06f388994500297bb91be60ffaf6825ecfd2afe",
        "https://git.kernel.org/stable/c/de5bd24197bd9ee37ec1e379a3d882bbd15c5065",
        "https://git.kernel.org/stable/c/e22a97700901ba5e8bf8db68056a0d50f9440cae",
        "https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/21xxx/CVE-2025-21820.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-21820",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
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    "related_cves": [
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        "value": "CVE-2025-21820",
        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 499808,
  "published_at": "2025-02-27T20:04:17.93+00:00"
}