Bug 2025645 (CVE-2021-4001)

Summary: CVE-2021-4001 kernel: race condition when the EBPF map is frozen
Product: [Other] Security Response Reporter: Guilherme de Almeida Suckevicz <gsuckevi>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: acaringi, adscvr, airlied, alciregi, bdettelb, bhu, bskeggs, chwhite, dhoward, dvlasenk, hdegoede, hkrzesin, jarod, jarodwilson, jburrell, jeremy, jforbes, jglisse, jlelli, jonathan, josef, jshortt, jstancek, jwboyer, kcarcia, kernel-maint, kernel-mgr, lgoncalv, linville, masami256, mchehab, nmurray, ptalbert, qzhao, rkeshri, rvrbovsk, steved, swood, vkumar, walters, williams
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: kernel 5.16 rc2 Doc Type: If docs needed, set a value
Doc Text:
A race condition was found in the Linux kernel's ebpf verifier between bpf_map_update_elem and bpf_map_freeze due to a missing lock in kernel/bpf/syscall.c. In this flaw, a local user with a special privilege (cap_sys_admin or cap_bpf) can modify the frozen mapped address space.
 Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Bug Depends On: 2025646, 2027593, 2029194, 2029195, 2029196, 2029197, 2029198    
Bug Blocks: 2024668, 2025647    

Description Guilherme de Almeida Suckevicz 2021-11-22 16:34:57 UTC 
A race problem is found in the ebpf verifier between bpf_map_update_elem and bpf_map_freeze due to a missing lock in kernel/bpf/syscall.c. In this flaw, a local user with a special privilege (cap_sys_admin or cap_bpf) can modify the frozen mapped address space.

Reference and upstream patch:
https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=353050be4c19e102178ccc05988101887c25ae53
Comment 1 Guilherme de Almeida Suckevicz 2021-11-22 16:35:58 UTC 
Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 2025646]