Linux Kernel MIPS ftrace: Memory Corruption when Kernel > 32bit
CVE-2025-71109 Published on January 14, 2026
MIPS: ftrace: Fix memory corruption when kernel is located beyond 32 bits
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.
Products Associated with CVE-2025-71109
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Affected Versions
Linux:- Version e424054000878d7eb11e44289242886d6e219d22 and below e3e33ac2eb69d595079a1a1e444c2fb98efdd42d is affected.
- Version e424054000878d7eb11e44289242886d6e219d22 and below 7f39b9d0e86ed6236b9a5fb67616ab1f76c4f150 is affected.
- Version e424054000878d7eb11e44289242886d6e219d22 and below 36dac9a3dda1f2bae343191bc16b910c603cac25 is affected.
- Version 2.6.35 is affected.
- Before 2.6.35 is unaffected.
- Version 6.12.64, <= 6.12.* is unaffected.
- Version 6.18.3, <= 6.18.* is unaffected.
- Version 6.19, <= * is unaffected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.