Bug 2276375

Summary:	Missing randomized slab caches for normal kmalloc: enable CONFIG_RANDOM_KMALLOC_CACHES=y
Product:	[Fedora] Fedora	Reporter:	jvoisin <julien.voisin+fedora>
Component:	kernel	Assignee:	Kernel Maintainer List <kernel-maint>
Status:	CLOSED ERRATA	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	medium	Docs Contact:
Priority:	unspecified
Version:	40	CC:	acaringi, adscvr, airlied, alciregi, bskeggs, hdegoede, hpa, jarod, josef, kernel-maint, linville, masami256, mchehab, ptalbert, steved
Target Milestone:	---	Keywords:	RFE, Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	kernel-6.8.9-200.fc39 kernel-6.8.9-100.fc38 kernel-6.8.9-300.fc40	Doc Type:	---
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2024-05-10 01:05:17 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description jvoisin 2024-04-22 11:08:24 UTC

1. Please describe the problem:

It's currently trivial to perform heap feng-shui on Fedora to exploit heap-related memory corruption like use-after-free or types-confusion. Enabling CONFIG_RANDOM_KMALLOC_CACHES would make it arguably harder for attacker to produce reliable exploits. It's a ~150LoC not-so-bad security mitigation with performance impact in the noise level, I don't see why it shouldn't be enabled by default.

See the following links for in-detail analysis:

- https://dustri.org/b/some-notes-on-randomized-slab-caches-for-kmalloc.html
- https://sam4k.com/exploring-linux-random-kmalloc-caches/
- https://lwn.net/Articles/938246/

2. What is the Version-Release number of the kernel:

N/A

3. Did it work previously in Fedora? If so, what kernel version did the issue
*first* appear? Old kernels are available for download at
https://koji.fedoraproject.org/koji/packageinfo?packageID=8 :

4. Can you reproduce this issue? If so, please provide the steps to reproduce
the issue below:

Yes, rebuild with `CONFIG_RANDOM_KMALLOC_CACHES=y` and notice that nothing breaks.

5. Does this problem occur with the latest Rawhide kernel? To install the
Rawhide kernel, run ``sudo dnf install fedora-repos-rawhide`` followed by
``sudo dnf update --enablerepo=rawhide kernel``:

N/A

6. Are you running any modules that not shipped with directly Fedora's kernel?:

N/A

7. Please attach the kernel logs. You can get the complete kernel log
for a boot with ``journalctl --no-hostname -k > dmesg.txt``. If the
issue occurred on a previous boot, use the journalctl ``-b`` flag.

N/A

Reproducible: Always

Comment 1 Fedora Update System 2024-05-03 00:44:54 UTC

FEDORA-2024-e513c6594d (kernel-6.8.9-100.fc38) has been submitted as an update to Fedora 38.
https://bodhi.fedoraproject.org/updates/FEDORA-2024-e513c6594d

Comment 2 Fedora Update System 2024-05-03 00:44:56 UTC

FEDORA-2024-c90afc5c01 (kernel-6.8.9-300.fc40) has been submitted as an update to Fedora 40.
https://bodhi.fedoraproject.org/updates/FEDORA-2024-c90afc5c01

Comment 3 Fedora Update System 2024-05-03 00:44:58 UTC

FEDORA-2024-3697e3b459 (kernel-6.8.9-200.fc39) has been submitted as an update to Fedora 39.
https://bodhi.fedoraproject.org/updates/FEDORA-2024-3697e3b459

Comment 4 Fedora Update System 2024-05-04 02:14:15 UTC

FEDORA-2024-e513c6594d has been pushed to the Fedora 38 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2024-e513c6594d`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2024-e513c6594d

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Comment 5 Fedora Update System 2024-05-04 03:17:42 UTC

FEDORA-2024-3697e3b459 has been pushed to the Fedora 39 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2024-3697e3b459`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2024-3697e3b459

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Comment 6 Fedora Update System 2024-05-04 03:37:55 UTC

FEDORA-2024-c90afc5c01 has been pushed to the Fedora 40 testing repository.
Soon you'll be able to install the update with the following command:
`sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2024-c90afc5c01`
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2024-c90afc5c01

See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.

Comment 7 Fedora Update System 2024-05-10 01:05:17 UTC

FEDORA-2024-3697e3b459 (kernel-6.8.9-200.fc39) has been pushed to the Fedora 39 stable repository.
If problem still persists, please make note of it in this bug report.

Comment 8 Fedora Update System 2024-05-10 01:34:31 UTC

FEDORA-2024-e513c6594d (kernel-6.8.9-100.fc38) has been pushed to the Fedora 38 stable repository.
If problem still persists, please make note of it in this bug report.

Comment 9 Fedora Update System 2024-05-10 02:59:15 UTC

FEDORA-2024-c90afc5c01 (kernel-6.8.9-300.fc40) has been pushed to the Fedora 40 stable repository.
If problem still persists, please make note of it in this bug report.