Bug 1225057 (CVE-2021-47318)

Summary: VUL-0: CVE-2021-47318: kernel: arch_topology: avoid use-after-free for scale_freq_data
Product: [Novell Products] SUSE Security Incidents Reporter: SMASH SMASH <smash_bz>
Component: IncidentsAssignee: Security Team bot <security-team>
Status: RESOLVED FIXED QA Contact: Security Team bot <security-team>
Severity: Major    
Priority: P2 - High CC: camila.matos, jlee, meissner
Version: unspecified   
Target Milestone: ---   
Hardware: Other   
OS: Other   
URL: https://smash.suse.de/issue/406954/
Whiteboard: CVSSv3.1:SUSE:CVE-2021-47318:7.0:(AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H)
Found By: Security Response Team Services Priority:
Business Priority: Blocker: ---
Marketing QA Status: --- IT Deployment: ---
Bug Depends on:    
Bug Blocks: 1227499    

Description SMASH SMASH 2024-05-22 17:33:50 UTC 
In the Linux kernel, the following vulnerability has been resolved:

arch_topology: Avoid use-after-free for scale_freq_data

Currently topology_scale_freq_tick() (which gets called from
scheduler_tick()) may end up using a pointer to "struct
scale_freq_data", which was previously cleared by
topology_clear_scale_freq_source(), as there is no protection in place
here. The users of topology_clear_scale_freq_source() though needs a
guarantee that the previously cleared scale_freq_data isn't used
anymore, so they can free the related resources.

Since topology_scale_freq_tick() is called from scheduler tick, we don't
want to add locking in there. Use the RCU update mechanism instead
(which is already used by the scheduler's utilization update path) to
guarantee race free updates here.

synchronize_rcu() makes sure that all RCU critical sections that started
before it is called, will finish before it returns. And so the callers
of topology_clear_scale_freq_source() don't need to worry about their
callback getting called anymore.

References:
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-47318
https://www.cve.org/CVERecord?id=CVE-2021-47318
https://git.kernel.org/stable/c/83150f5d05f065fb5c12c612f119015cabdcc124
https://git.kernel.org/stable/c/ccdf7e073170886bc370c613e269de610a794c4a
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2021/CVE-2021-47318.mbox
Comment 1 Joey Lee 2024-05-23 04:44:03 UTC 
joeyli@linux-691t:/mnt/working/source_code-git/kernel-source> ./scripts/check-kernel-fix CVE-2021-47318
83150f5d05f0 ("arch_topology: Avoid use-after-free for scale_freq_data") merged v5.14-rc1~47^2~1^2^2~1
Fixes: 01e055c120a4 ("arch_topology: Allow multiple entities to provide sched_freq_tick() callback") merged v5.13-rc1~156^2~4^2~1^2~14
Security fix for CVE-2021-47318 bsc#1225057 with CVSS 7
Experts candidates: tiwai@suse.de 
..............................
NO ACTION NEEDED: All relevant branches contain the fix!

This issue did not affect any kernel branch. reset assigner
Comment 2 Gabriele Sonnu 2024-06-07 15:38:06 UTC 
All done, closing.