FKIE_CVE-2025-71109

Vulnerability from fkie_nvd - Published: 2026-01-14 15:15 - Updated: 2026-01-14 16:25
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: MIPS: ftrace: Fix memory corruption when kernel is located beyond 32 bits Since commit e424054000878 ("MIPS: Tracing: Reduce the overhead of dynamic Function Tracer"), the macro UASM_i_LA_mostly has been used, and this macro can generate more than 2 instructions. At the same time, the code in ftrace assumes that no more than 2 instructions can be generated, which is why it stores them in an int[2] array. However, as previously noted, the macro UASM_i_LA_mostly (and now UASM_i_LA) causes a buffer overflow when _mcount is beyond 32 bits. This leads to corruption of the variables located in the __read_mostly section. This corruption was observed because the variable __cpu_primary_thread_mask was corrupted, causing a hang very early during boot. This fix prevents the corruption by avoiding the generation of instructions if they could exceed 2 instructions in length. Fortunately, insn_la_mcount is only used if the instrumented code is located outside the kernel code section, so dynamic ftrace can still be used, albeit in a more limited scope. This is still preferable to corrupting memory and/or crashing the kernel.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/36dac9a3dda1f2bae343191bc16b910c603cac25
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7f39b9d0e86ed6236b9a5fb67616ab1f76c4f150
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e3e33ac2eb69d595079a1a1e444c2fb98efdd42d
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{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nMIPS: ftrace: Fix memory corruption when kernel is located beyond 32 bits\n\nSince commit e424054000878 (\"MIPS: Tracing: Reduce the overhead of\ndynamic Function Tracer\"), the macro UASM_i_LA_mostly has been used,\nand this macro can generate more than 2 instructions. At the same\ntime, the code in ftrace assumes that no more than 2 instructions can\nbe generated, which is why it stores them in an int[2] array. However,\nas previously noted, the macro UASM_i_LA_mostly (and now UASM_i_LA)\ncauses a buffer overflow when _mcount is beyond 32 bits. This leads to\ncorruption of the variables located in the __read_mostly section.\n\nThis corruption was observed because the variable\n__cpu_primary_thread_mask was corrupted, causing a hang very early\nduring boot.\n\nThis fix prevents the corruption by avoiding the generation of\ninstructions if they could exceed 2 instructions in\nlength. Fortunately, insn_la_mcount is only used if the instrumented\ncode is located outside the kernel code section, so dynamic ftrace can\nstill be used, albeit in a more limited scope. This is still\npreferable to corrupting memory and/or crashing the kernel."
    }
  ],
  "id": "CVE-2025-71109",
  "lastModified": "2026-01-14T16:25:12.057",
  "metrics": {},
  "published": "2026-01-14T15:15:59.973",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/36dac9a3dda1f2bae343191bc16b910c603cac25"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/7f39b9d0e86ed6236b9a5fb67616ab1f76c4f150"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e3e33ac2eb69d595079a1a1e444c2fb98efdd42d"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}


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