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Medium severity5.5NVD Advisory· Published Jul 29, 2024· Updated May 12, 2026

CVE-2024-42096

CVE-2024-42096

Description

In the Linux kernel, the following vulnerability has been resolved:

x86: stop playing stack games in profile_pc()

The 'profile_pc()' function is used for timer-based profiling, which isn't really all that relevant any more to begin with, but it also ends up making assumptions based on the stack layout that aren't necessarily valid.

Basically, the code tries to account the time spent in spinlocks to the caller rather than the spinlock, and while I support that as a concept, it's not worth the code complexity or the KASAN warnings when no serious profiling is done using timers anyway these days.

And the code really does depend on stack layout that is only true in the simplest of cases. We've lost the comment at some point (I think when the 32-bit and 64-bit code was unified), but it used to say:

Assume the lock function has either no stack frame or a copy of eflags from PUSHF.

which explains why it just blindly loads a word or two straight off the stack pointer and then takes a minimal look at the values to just check if they might be eflags or the return pc:

Eflags always has bits 22 and up cleared unlike kernel addresses

but that basic stack layout assumption assumes that there isn't any lock debugging etc going on that would complicate the code and cause a stack frame.

It causes KASAN unhappiness reported for years by syzkaller [1] and others [2].

With no real practical reason for this any more, just remove the code.

Just for historical interest, here's some background commits relating to this code from 2006:

0cb91a229364 ("i386: Account spinlocks to the caller during profiling for !FP kernels") 31679f38d886 ("Simplify profile_pc on x86-64")

and a code unification from 2009:

ef4512882dbe ("x86: time_32/64.c unify profile_pc")

but the basics of this thing actually goes back to before the git tree.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

The Linux kernel's profile_pc() function makes unsafe stack layout assumptions, causing KASAN warnings; the fix removes the flawed code.

Vulnerability

Description

The profile_pc() function in the x86 architecture of the Linux kernel is used for timer-based profiling. It attempts to attribute time spent in spinlocks to the caller by inspecting the stack, assuming a specific stack layout (no stack frame or a copy of eflags from PUSHF). This assumption is not guaranteed, especially with lock debugging enabled, leading to KASAN (Kernel Address Sanitizer) warnings and potential instability [1][2].

Exploitation

The issue is not directly exploitable for privilege escalation but can be triggered by any timer-based profiling activity on affected kernels. No special privileges are required; it occurs during normal kernel profiling operations. The function's assumptions about stack layout can be violated by various kernel configurations and debugging features, making it a reliability concern rather than a security boundary violation.

Impact

The primary impact is the generation of false positive KASAN reports, which can mask real bugs and cause system instability or denial of service. The vulnerability is listed in Siemens security advisories affecting products like SIMATIC S7-1500 TM MFP - GNU/Linux subsystem [1][2].

Mitigation

The fix removes the problematic code entirely, as the timer-based profiling functionality is no longer considered critical. Patches are available in the stable kernel tree [3][4]. Users should update to a patched kernel version to eliminate the warnings and potential instability.

References
  1. SSA-265688
  2. SSA-398330
  3. Making sure you're not a bot!
  4. Making sure you're not a bot!

AI Insight generated on May 20, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected products

184

Patches

0

No patches discovered yet.

Vulnerability mechanics

AI mechanics synthesis has not run for this CVE yet.

References

11

News mentions

0

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