CVE-2024-50263: fork: only invoke khugepaged, ksm hooks if no error
First published: Mon Nov 11 2024(Updated: )
In the Linux kernel, the following vulnerability has been resolved: fork: only invoke khugepaged, ksm hooks if no error There is no reason to invoke these hooks early against an mm that is in an incomplete state. The change in commit d24062914837 ("fork: use __mt_dup() to duplicate maple tree in dup_mmap()") makes this more pertinent as we may be in a state where entries in the maple tree are not yet consistent. Their placement early in dup_mmap() only appears to have been meaningful for early error checking, and since functionally it'd require a very small allocation to fail (in practice 'too small to fail') that'd only occur in the most dire circumstances, meaning the fork would fail or be OOM'd in any case. Since both khugepaged and KSM tracking are there to provide optimisations to memory performance rather than critical functionality, it doesn't really matter all that much if, under such dire memory pressure, we fail to register an mm with these. As a result, we follow the example of commit d2081b2bf819 ("mm: khugepaged: make khugepaged_enter() void function") and make ksm_fork() a void function also. We only expose the mm to these functions once we are done with them and only if no error occurred in the fork operation.
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Linux Kernel | >=6.8<6.11.7 | |
| Linux Kernel | =6.12-rc1 | |
| Linux Kernel | =6.12-rc2 | |
| Linux Kernel | =6.12-rc3 | |
| Linux Kernel | =6.12-rc4 | |
| Linux Kernel | =6.12-rc5 | |
| debian/linux | 5.10.223-1 5.10.226-1 6.1.123-1 6.1.128-1 6.12.12-1 6.12.15-1 |
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Reference Links
- https://git.kernel.org/stable/c/3b85aa0da8cd01173b9afd1f70080fbb9576c4b0
- https://git.kernel.org/stable/c/985da552a98e27096444508ce5d853244019111f
- https://project-zero.issues.chromium.org/issues/373391951
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-50263
- https://nvd.nist.gov/vuln/detail/CVE-2024-50263
- https://launchpad.net/bugs/cve/CVE-2024-50263
- https://security-tracker.debian.org/tracker/CVE-2024-50263
- https://ubuntu.com/security/CVE-2024-50263
- https://git.kernel.org/linus/985da552a98e27096444508ce5d853244019111f
Frequently Asked Questions
What is the severity of CVE-2024-50263?
CVE-2024-50263 has been classified with a low severity level due to its specific conditions requiring incomplete memory states.
How do I fix CVE-2024-50263?
To fix CVE-2024-50263, upgrade the Linux kernel to version 6.12-rc6 or later.
Which versions of the Linux kernel are affected by CVE-2024-50263?
CVE-2024-50263 affects Linux kernel versions from 6.8 to 6.11.7 and 6.12-rc1 through 6.12-rc5.
What types of exploits are possible with CVE-2024-50263?
Exploiting CVE-2024-50263 may lead to unexpected behavior in memory management during the fork operation.
Is there a workaround for CVE-2024-50263?
There are no known workarounds for CVE-2024-50263 other than applying the kernel update.
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