Homepage

CVE-2024-42096 Affecting kernel-rt-debug-modules-extra package, versions <0:4.18.0-553.22.1.rt7.363.el8_10

Severity

 Recommended
high

Based on AlmaLinux security rating.

Threat Intelligence

EPSS
0.04% (15th percentile)

Do your applications use this vulnerable package?

In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.

Test your applications
  • Snyk IDSNYK-ALMALINUX8-KERNELRTDEBUGMODULESEXTRA-8096896
  • published25 Sept 2024
  • disclosed11 Sept 2024
Report a new vulnerability Found a mistake?

Introduced: 11 Sep 2024

CVE-2024-42096  (opens in a new tab)

How to fix?

Upgrade AlmaLinux:8 kernel-rt-debug-modules-extra to version 0:4.18.0-553.22.1.rt7.363.el8_10 or higher.
This issue was patched in ALSA-2024:7001.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-rt-debug-modules-extra package and not the kernel-rt-debug-modules-extra package as distributed by AlmaLinux. See How to fix? for AlmaLinux:8 relevant fixed versions and status.

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.

References

CVSS Scores

version 3.1