{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2025-22035",
  "modified": "2026-10-09T11:39:44Z",
  "upstream": [
    "CVE-2025-22035"
  ],
  "published": "2025-04-16T14:14:59Z",
  "summary": "tracing: Fix use-after-free in print_graph_function_flags during tracer switching",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Fix use-after-free in print_graph_function_flags during tracer switching\n\nKairui reported a UAF issue in print_graph_function_flags() during\nftrace stress testing [1]. This issue can be reproduced if puting a\n'mdelay(10)' after 'mutex_unlock(&trace_types_lock)' in s_start(),\nand executing the following script:\n\n  $ echo function_graph > current_tracer\n  $ cat trace > /dev/null &\n  $ sleep 5  # Ensure the 'cat' reaches the 'mdelay(10)' point\n  $ echo timerlat > current_tracer\n\nThe root cause lies in the two calls to print_graph_function_flags\nwithin print_trace_line during each s_show():\n\n  * One through 'iter->trace->print_line()';\n  * Another through 'event->funcs->trace()', which is hidden in\n    print_trace_fmt() before print_trace_line returns.\n\nTracer switching only updates the former, while the latter continues\nto use the print_line function of the old tracer, which in the script\nabove is print_graph_function_flags.\n\nMoreover, when switching from the 'function_graph' tracer to the\n'timerlat' tracer, s_start only calls graph_trace_close of the\n'function_graph' tracer to free 'iter->private', but does not set\nit to NULL. This provides an opportunity for 'event->funcs->trace()'\nto use an invalid 'iter->private'.\n\nTo fix this issue, set 'iter->private' to NULL immediately after\nfreeing it in graph_trace_close(), ensuring that an invalid pointer\nis not passed to other tracers. Additionally, clean up the unnecessary\n'iter->private = NULL' during each 'cat trace' when using wakeup and\nirqsoff tracers.\n\n [1] https://lore.kernel.org/all/20231112150030.84609-1-ryncsn@gmail.com/",
  "severity": [
    {
      "type": "CVSS_V3",
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
    }
  ],
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  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-22035"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/42561fe62c3628ea3bc9623f64f047605e98857f"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/de7b309139f862a44379ecd96e93c9133c69f813"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/81a85b12132c8ffe98f5ddbdc185481790aeaa1b"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/a2cce54c1748216535dda02e185d07a084be837e"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/099ef3385800828b74933a96c117574637c3fb3a"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/c85efe6e13743cac6ba4ccf144cb91f44c86231a"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/f14752d66056d0c7bffe5092130409417d3baa70"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/70be951bc01e4a0e10d443f3510bb17426f257fb"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/7f81f27b1093e4895e87b74143c59c055c3b1906"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T12:19:11Z",
    "severity": {
      "source": "kernel CNA",
      "cvss_v3_score": 7.8,
      "cvss_v3_severity": "High",
      "scenario": "AV:L - The vulnerability is reached only through local file operations on tracefs \u2014 reading `/sys/kernel/tracing/trace` while writing `current_tracer`. There is no network, adjacent-network, or physical path into `print_graph_function_flags()`.\nAC:L - The attacker owns both sides of the sequence \u2014 its own paced reader (small `read()` buffers, or SIGSTOP) and its own `current_tracer` write \u2014 so the free in `s_start()` and the use in `s_show()` can be ordered deterministically without winning any race. Once freed, `iter->private` stays dangling for the rest of the iterator's life, giving unlimited time to groom the ~128-byte slab.\nPR:L - `tracing_check_open_get_tr()` enforces no capability check at all \u2014 only kernel lockdown, which is off by default \u2014 so reachability is governed purely by tracefs permissions, and tracefs's `gid=` mount option is widely used (Android, ChromeOS, CI/perf and developer systems, containers with tracefs bind-mounted) to grant an unprivileged tracing group read/write on `trace` and `current_tracer`.\nUI:N - The attacker performs both the file read and the tracer switch itself; no victim action or pre-existing session state is needed.\nS:U - The freed object and all corrupted memory belong to the kernel itself, and exploitation yields kernel privileges within the same security authority \u2014 no VM, IOMMU, or sandbox boundary is crossed.\nC:H - This is a use-after-free on a general-purpose kmalloc object, so a heap spray gives the attacker control of `data->cpu_data`, and `per_cpu_ptr(data->cpu_data, cpu)->ignore` then reads arbitrary kernel memory; the `data->failed` path additionally formats attacker-supplied `data->ent.ent` function addresses through `print_graph_entry()` straight into the trace output the attacker reads back.\nI:H - `per_cpu_ptr(data->cpu_data, cpu)->ignore = 0` and `= 1` are writes through a pointer taken from freed, sprayable memory, yielding an arbitrary-address write primitive, and the attacker-controlled `data->cpu` is used as an unchecked per-CPU index \u2014 a classic UAF path to privilege escalation.\nA:H - Dereferencing the freed `fgraph_data` and its stale percpu pointer oopses or panics the kernel even without successful grooming, and the read can be repeated at will to crash the machine reliably."
    }
  }
}